Climate Change Vulnerability Assessment for Boeung Chhmar

Climate change vulnerability assessment for Boeung Chhmar

Mekong Water Dialogues Peter-John Meynell, Kimsreng Kong, Pheakdey Sorn and Vanny Lou

The designation of geographical entities in Citation: Meynell, P. J., Kong, K., Sorn, this book, and the presentation of the Pheakdey. and Lou, V. (2014). Climate material, do not imply the expression of change vulnerability assessment for any opinion whatsoever on the part of Boeung Chhmar. Thailand: IUCN. IUCN or the concerning the legal status of 120pp. any country, territory, or area, or of its authorities, or concerning the delimitation Cover photo: © IUCN Cambodia of its frontiers or boundaries. The views expressed in this publication do not Layout by: Ria Sen/Nguyen Thuy Anh necessarily reflect those of IUCN, the Ministry of Foreign Affairs of Finland, Produced by: IUCN Southeast Asia European Union or any other participating Group organizations. Available from: IUCN Asia Regional This publication has been made possible Office, 63 Soi Prompong, Sukhumvit 39, by funding from the Ministry of Foreign Wattana 10110 Bangkok, Thailand Affairs for Finland and European Union. Tel: +66 2 662 4029

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Contents

Acknowledgements ...... 9 Acronyms and abbreviations ...... 10 Executive summary ...... 11 1 Introduction ...... 17 2 Methods ...... 19 2.1 Wetland and climate change case studies guidance ...... 19 2.2 VCA ...... 21 2.3 Climate Change Adaptation and Mitigation Methodology (CAM) ...... 21 2.4 Determining ecological response to climate change ...... 25 2.4.1 Comfort zones ...... 26 3 Description of Boeung Chhmar ...... 28 3.1 Hydrological characteristics...... 30 3.1.1 The Tonle Sap system ...... 30 3.1.2 Boeung Chhmar ...... 31 3.2 Habitats – area and extent ...... 32 3.3 Seasonal ecological processes ...... 37 3.4 Key species ...... 38 3.4.1 Fish ...... 38 3.4.2 Invertebrates ...... 40 3.4.3 Large water birds ...... 41 3.4.4 Mammals ...... 43 3.4.5 Reptiles ...... 43 3.5 Community conservation sites ...... 45 3.6 Communities and key livelihood activities ...... 45 3.7 Perceived non-climate threats and changes ...... 46 4 Management and institutional situation ...... 47 4.1 Ramsar site ...... 47 4.2 Management plan ...... 48 4.3 Abolition of fishing lot #6 and implications ...... 48 5 Climate – present and future ...... 49 5.1 Current climate ...... 49

5.2 Future projections ...... 50 5.2.1 Climate projection methods ...... 51 5.2.2 Temperature changes...... 51 5.2.3 Rainfall...... 56 5.2.4 Storms and extreme events ...... 59 5.3 Local perceptions of climate trends and extreme events ...... 60 5.4 Hydrology and habitat changes ...... 61 6 Vulnerability assessment ...... 69 6.1 Summary of main climate threats ...... 69 6.2 Vulnerability of key physical and ecological processes ...... 70 6.3 Key habitats ...... 75 6.3.1 Open water ...... 75 6.3.2 Gallery forest – alongside Tonle Sap and along river banks...... 76 6.3.3 Mixed flooded shrubland with trees ...... 78 6.3.4 Flooded grassland ...... 78 6.4 Vulnerability assessments of key plant species ...... 79 6.4.1 Swamp forest trees – Barringtonia sp ...... 79 6.4.2 Shrubs – Sesbania sesban ...... 80 6.4.3 Shrubs – Mimosa pigra ...... 81 6.5 Vulnerability assessments of key fauna ...... 81 6.5.1 Fish ...... 81 6.5.2 Eel ...... 85 6.5.3 Crustacea - Rice field Shrimp – Machrobrachium lanchesteri ...... 86 6.5.4 Snails – Pila scutata and Pomacea canaliculata ...... 88 6.5.5 Reptiles – Water snakes ...... 89 6.5.6 Turtles...... 91 6.5.7 Large water birds ...... 93 6.5.8 Mammals ...... 93 7 Vulnerability of livelihood activities in Boeung Chhmar ...... 94 7.1 Fishing ...... 94 7.2 Fish raising ...... 101 7.3 Fishing supporting activities ...... 101 7.4 Water supply ...... 101

7.5 NTFP collection ...... 102 7.6 Ecotourism ...... 102 8 Conclusion ...... 103 References ...... 105 Annex 1: CAM matrices of the key habitats ...... 107 Annex 2: CAM matrices of selected species ...... 114 Annex 3: CAM matrices of fish species from Mekong ARCC Fisheries study 118

List of figures and tables

Figures

Figure 2.1 Nine steps approach for wetland and climate change case studies

Figure 2.2 Vulnerability assessment and adaptation process

Figure 2.3 Climate change impact and vulnerability assessment process

Figure 2.4 Parameters and issues considered in the baseline and vulnerability assessment process

Figure 2.5 Summary of some of the predicted aspects of climate change and examples of the effects that these are likely to have on species

Figure 2.6 Maximum temperature comfort zone analysis of temperature range shifts in wet and dry season, Kampong Thom Province

Figure 3.1 Overview map of the Tonle Sap with major land use/land cover classes from JICA (1999) below 15 m asl and water depth measurements

Figure 3.2 Map of Boeung Chhmar Ramsar site

Figure 3.3 Satellite imagery of Boueng Chhmar, showing bodies of open water and creek system

Figure 3.4 Cross section of floodplain habitats in Kampong Thom province during a) October/November and b) May/June

Figure 3.5 Vertical distribution of dominant plant species in the Tonle Sap floodplain (to 6 m elevation)

Figure 3.6 Map of key habitats in Boeung Chhmar Ramsar Site

Figure 5.1 Monthly maximum and minimum temperatures at Kampong Thom, 2002- 2010

Figure 5.2 Monthly mean maximum temperature at Kampong Thom provincial town, 2002- 2010

Figure 5.3 Rainfall measured at Kampong Thom station from 2000-2010

Figure 5.4 Monthly average rainfall, measured at Kampong Thom station

Figure 5.5 Monthly average temperatures for baseline (1980-2004) and climate models (2045-2069)

Figure 5.6 Maximum temperatures for baseline (1980-2004) and climate change models (2045-2069)

Figure 5.7 Daily maximum temperatures for baseline (1980-2004) and climate change models (2045-2069)

Figure 5.8 Daily minimum temperatures for baseline (1980-2004) and climate change models (2045-2069)

Figure 5.9 Annual proportion of daily exceedance of maximum (left) and minimum (right) temperatures

Figure 5.10 Maximum temperature comfort zone analysis of temperature range shifts, differentiated by wet and dry season (left) and over the whole year (right)

Figure 5.11 Minimum temperature comfort zone analysis of temperature range shifts, differentiated by wet and dry season (left) and over the whole year (right)

Figure 5.12 Combined maximum and minimum comfort zones for Boeung Chhmar

Figure 5.13 Average monthly rainfall at Boeung Chhmar, baseline and future climate change (2045-2069)

Figure 5.14 Total rainfall vs total number of days of precipitation, dry season (left) wet season right for baseline and GCM average

Figure 5.15 Start of the monsoon as indicated by first month of the year in which the rainfall exceeds 200 mm

Figure 5.16 Ecological comfort zones for rainfall for Boeung Chhmar, by wet and dry season (left) and combined for the whole year (right)

Figure 5.17 Annual average precipitation and % precipitation change in 2050 in Kampong Thom province, Cambodia

Figure 5.18 Ranking of annual maximum rainfall events

Figure 6.1 Comparison of mean monthly water levels at Kampong Loung for historical observed records and model predictions for a) an average year, b) a dry year and c) a wet year.

Figure 6.2 Annual flood duration (months) and extent during a) an average year, b) dry year and c) wet year

Figure 6.3 Flood duration (months) zone dominance - % of flood zone area covered by each of five habitat types during a) average years, b) dry years, c) wet years

Figure 6.5 Spatial extent of flooding in a) dry season – increase of about 30% compared to baseline (left) and b) wet season – decrease of -10% compared to baseline (right)

Figure 6.6 Habitat changes from the baseline around Boeung Chhmar due to upstream hydropower development in 2030s and Climate change in 2040’s

Tables

Table 2.1 Determining impact – Exposure X Sensitivity

Table 2.2 Determining vulnerability – Impact / Adaptive capacity

Table 3.1 Seasonal calendar of different physical and ecological process in the Tonle Sap

Table 3.2 Fish species of conservation concern in the Boeung Chhmar Ramsar site

Table 3.3 Waterbird species of conservation concern in Boeung Chhmar Ramsar site

Table 6.1 Flood duration rules used for modelling habitat cover in the Tonle Sap

Table 6.2 Area changes in modelled habitat cover from the baseline as a response to future scenarios

Table 7.1 Main climate changes expected at different seasons and possible impacts on key physical and ecological processes in Tonle Sap

Table 7.2 Optimum water temperature ranges for commonly cultured fish in the Lower Mekong Basin

Table 7.3 CAM Matrix summary for Machrobrachium lanchesteri

Table 7.4 CAM vulnerability assessment matrix for both species of turtle found in Boeung Chhmar

Table 8.1 Summary of climate change vulnerabilities of components of the Boeung Chhmar ecosystem

Acknowledgements

The authors would like to acknowledge the support and assistance of the following people and organisations without whom this study would not have been possible; the rangers of the Boeung Chhmar Ramsar site; the community leaders and people consulted in the core villages in the Boeung Chhmar Ramsar site, Dr. Srey Sunleang, director of department of wetlands and coastal zones of GDANCP, MoE, especially the deep sense of thanks to H.E Say Samal, Minister of Environment in Cambodia. The method of analysing vulnerability to climate change, the CAM, was developed by Dr Jeremy Carew Reid and his associates in the International Centre for Environmental Management, ICEM, and the climate change projection for Kampong Thom province was provided by ICEM as part of their work on the USAID funded Mekong ARCC project. The funding for this study came from the Mekong Water Dialogues project funded by the Government of Finland.

Acronyms and abbreviations

3S Sekong, Sesan and Srepok Rivers BCA Biodiversity Conservation Area CCAI Climate Change Adaptation Initiative CCD Climate Change Department CFi Community Fisheries site CPA Community Protected Area EIA Environmental Impact Assessment IBA Important Bird Area ICEM International Centre for Environmental Management IPCC International Panel on Climate Change IUCN International Union for Conservation of Nature FiA Fisheries Administration GCM Global Circulation Model GDANCP General Department of Administration for Nature Conservation and Protection Km Kilometre LSS Lower Stung Sen M Metre MAFF Ministry of Agriculture, Forestry and Fisheries MEA Millennium Ecosystem Assessment MoE Ministry of Environment MRC Mekong River Commission NCDM National Committee for Disaster Management NGO Non-Governmental Organisation NIS National Institute of Statistics NMC National Mekong Committee NTFP Non Timber Forest Product PA Protected Area PRA Participatory Rapid Appraisal PPA Participatory Poverty Assessment SEA Southeast Asia Global Change System for Analysis, Research & Training START Network, Regional Centre TSA Tonle Sap Authority UNESCO United Nations Education, Scientific and Cultural Organisation WCD Department of Wetlands and Coastal Zones WEPA Water Environment Partnership in Asia

Executive summary

A vulnerability assessment of the impacts of climate change on the Ramsar site at Boeung Chhmar, one of the three core zones of the Tonle Sap Biosphere reserve in Cambodia has been carried out. This follows on from earlier vulnerability assessments that were carried out as part of the MRC’s study on wetlands and climate change in the Lower Mekong Basin, for which relevant case studies at Lower Stung Sen in Cambodia were particularly instructive in this assessment. In addition climate change projections for Kampong Thom province that had been prepared for the USAID funded Mekong ARCC project, were directly relevant and used for the downscaled projections at Boeung Chhmar. The thematic studies of the Mekong ARC project on fisheries, agriculture, livestock and NTFPs were also used and the vulnerability assessments for particular wild capture fisheries and aquaculture were tailored to the projected conditions in Boeung Chhmar. In addition a recent vulnerability assessment carried out in the Ramsar site of Beung Kiat Ngong in southern Lao PDR also provided parallel assessments for comparison.

The overall description of the wetland ecosystem and its components were drawn from the 2005 Status review of the Tonle Sap Biosphere Reserve, and the 2008 Management Plan for the Ramsar site at Boeung Chhmar. The statistics about the local communities and their perceptions about climate change were drawn from the 2013 IUCN Situation analysis at three project sites on the Tonle Sap Lake.

The Ramsar site of Boeung Chhmar and associated river system and floodplain was designated in 1999 and covers a total area of 28,000 ha of which 23,000 lies in Kampong Thom Province and 5,000 ha in Siem Reap province. The maximum elevation of the site is 10 m above sea level. The site consists of a permanent open water body of about 3,803 ha, surrounded by a complex creek system and flood plains, with flooded forest fringing the shores of the Tonle Sap and parts of the open water lake. The major habitats are the lake's open water and the vast inundated floodplain. Most of the plain can be classified as "seasonal freshwater swamp savannah". The hydrology of the site is largely determined by two rivers the Stung Staung and Stung Chikreng and the interaction with the adjacent Tonle Sap Great Lake. The creek systems are mostly shallow especially in April with a maximum depth of about 2 m. The lake is shallower at 0.5 to 1 m deep. During inundation the lake reaches a maximum depth of 4 m.

The key species found in the Ramsar site include the Black fish – residents, inhabiting relatively clear-water swamps and plains year round and making limited lateral migrations, the grey fish – opportunist small, fast growing species, and the White fish species mainly associated with the main channels and streams, and exhibit strong lateral and longitudinal migrations, including into floodplains. Eels are considered separately because of their importance to the fishery. Invertebrates include snails – Pila scutata and the invasive Golden Apple Snail, crustacean, such as the rice field crab and Machrobrachium lanchesteri. Boeung Chhmar is famous for the large water birds that come to feed especially during the later dry season, including Greater and Lesser Adjutants, Spot-billed Pelican, Painted and Milky Storks, Black-headed Ibis, Darter and Indian Cormorant. Boeung Chhmar is an important breeding area for the Tonle Sap water snakes and for turtles.

There are 5 villages within the Ramsar site with 645 households and a total population of 3,351. 65% of the people are poor and highly dependent upon fisheries as the main source of livelihood, both as source of income and for their own consumption. They have no agricultural fields, though they may have some small livestock and aquaculture cages.

The non-climate threats to the wetland include dry season rice farming in St. Staung causing water abstraction upstream of Boeung Chhmar, and depleting water levels in the lake during the late dry season; outsiders coming into fish dry season during March to June; illegal fishing using fishing techniques such as electric fishing and bag nets; invasion by mimosa pigra and water hyacinth. The removal of the commercial fishing lots has tended to reduce the fishing pressure on fish populations, in particular Fishing Lot No 6, which covered Boeung Chhmar, and associated disturbance and shooting of birds.

The projections for 2050 in Boeung Chhmar indicate that in the dry season, there is likely to be up to 3 deg C rise in maximum temperatures with the average daily maximum temperature rising steadily from 32oC in March to 35 oC with the hottest time extending through till mid-May. In the wet season the monthly maximum temperatures are expected to incrase by up to 4 deg C from 27.5 oC to over 31oC. The total average annual rainfall for the baseline is 1,249.3 mm/yr split between wet season of 975.1 mm from June to November and dry season of 274.2 mm from December to May. With climate change to 2050, this is expected to increase to 1381.4 mm per year split between wet season at 1,091.0 mm and dry season 290.4 mm. This represents an annual increase of 10.6%, a wet season increase of 11.9% and a dry season increase of 5.9%, though the distribution of rainfall in the dry season will be more variable, with small decreases during January and February and 7.5% decrease in April, counterbalanced by an increase in rainfall in May of 13.2%.

In terms of extreme events, there is likely to be an increase in heavy rainstorm with over 80 mm in a day each year from 7 to 11 events per year, and the intensity of the storms is also likely to increase, with the largest rainfall day increasing from 170 to 190 mm in a day. One of the features of the climate in Boeung Chhmar has been the incidence of sudden strong winds late in the dry season (April/May) which disturbs the shallow open water surface, and causes release of poor quality water, with massive fish kills resulting. It is likely that such events will increase.

The hydrology of the Tonle Sap and Boeung Chhmar is a very important ecological driver which will determine the extent of different wetland habitats. A recent paper by Arias et al. (2012) has attempted to quantify the changes in flooding and habitats in the Tonle Sap due to water infrastructure and climate change. This shows that during average years the mean water levels during the peak flood may be increased by 0.5 m due to climate change, which to some extent would be modified by a decrease due to water storage infrastructure. In dry years the changes are more pronounced. Area changes in seasonally flooded habitats in the wider Tonle Sap area would show an increase of about 7% due to climate change, but a decrease of about 13% due to infrastructure, with Gallery forests showing the greatest changes.

The Vulnerability assessments, which generally followed the CAM methodology developed by ICEM in the earlier studies, focused on the wetland habitats and ecosystem components that were directly used by the local communities.

Open water - The open water of Boeung Chhmar shows generally very high vulnerability to climate change which is likely to affect both the extent of the open water during the flood season and the depth and water quality of the open water in the dry season. Because it is so shallow, especially in the dry season, the water will become much hotter with the increased temperatures under climate change. It is particularly vulnerable to the strong winds that occur late in the dry season when the water is overturned and poor quality water is mixed up from the bottom layers, causing massive fish mortality.

Gallery forests - The gallery forests around Boeung Chhmar are particularly vulnerable to changes the water levels in the wet season and the depth and duration of the flood. Under climate change it is likely that expected that the wet season flooded area will increase slightly, but this may be moderated by the impacts of infrastructure development which will store water during the wet season. The dry season flooded area extent under climate change is likely to be reduced, but with infrastructure development, the flooded area extent will increase. This will threaten the survival of much of the flooded forest of Boeung Chhmar. For other aspects of climate change the gallery forest habitat is less vulnerable, though increased temperature at the time of flowering and fruiting may reduce the fertility of seeds. One of the main species, Barringtonia acutangula, is considered to have moderate vulnerability to climate change, principally for this reason, though it can adapt to prolonged inundation.

Shrublands - Shrubland habitats are generally quite resilient to climate changes and able to adapt to changes in water levels, and seasonal drying out. One of the main shrubs in the area, Sesbania sesban, has been shown to have low vulnerability to climate change, although the invasion into these areas by Mimosa pigra may increase with climate change.

Seasonally inundated grasslands - Grassland habitats appear to be quite resilient to changes in climate, with the highest temperatures occurring when the grasses and herbs have matured and seeded. There may be some changes in extent of the grassland areas especially at the deeper flooded grasslands, which may tend to evolve as flooded shrublands. Increased risk of fires in the dry season is part of natural grassland cycle and may control conversion to shrubland. There may be changes in the predominant species mix of the grassland, but the habitat will remain.

Impacts on some of the key species include:

Fish - Black fish tend to be less vulnerable to climate change because they are able to survive poor water quality conditions (low Dissolved Oxygen, low pH, high turbidity and high ammonia). Black fish are able to withstand harsh dry season environments including high temperatures and anoxic conditions and their limited migratory habits make them less vulnerable to wetlands fragmentation.

Most white fish species require higher water quality conditions in terms of Dissolved oxygen and alkalinity. They are more vulnerable to increased temperatures, especially at maturation and fry stages and more vulnerable to decreases in water availability e.g. in the dry season.

Fish and other aquatic animals in this ecological zone have evolved to survive the harsh conditions through the dry season and at the onset of the rains to mature quickly and breed. The survival of fish through the dry season depends to a large extent on the availability of

13 perennial waterbodies, such as in Boeung Chhmar. Shifting rainfall patterns, including longer dry periods could affect the survival of fish in the dry season.

Any changes in temperature will influence the metabolism, growth rate, reproduction, recruitment and susceptibility to toxins and disease. The response of fish to increased temperatures is likely to be a shift in behaviour and it could be that some species extend their ranges at the expense of others. Because of the higher tolerance of black fish to temperatures compared to white fish, there could be a shift towards greater populations of black fish.

Eels - are generally very hardy species able to tolerate climate extremes of drought and poor water quality and able to move overland to more favourable areas. In terms of climate change vulnerability, the Mekong ARCC fisheries study carried out a vulnerability assessment of an eel-like fish species, Mastacembalus armatus. The species is tolerant of high water temperatures and low dissolved oxygen, and the projected increases in temperature are within the tolerance range of the species. For M. armatus the drying out of water bodies during prolonged dry seasons would render it moderately vulnerable, but the swamp eel can move away to find other remaining bodies of water, and it can burrow into the mud and survive. Its vulnerability would therefore be low. Increased rainfall in the wet season, greater extent of the inundated area and flooding are likely to be beneficial for the species, providing both more habitat for the populations to expand into and larger populations of prey species.

Rice field shrimp - Machrobrachium lanchesterii - Ricefield shrimps appear to be tolerant of adverse water quality conditions and have a relatively prolific and adaptable breeding cycle. Of the various climate change threats the shrimp populations will be most vulnerable to drought and the drying out of shallow floodplain pools in the dry season. Populations living in the open water bodies will be able to survive drought, but may be susceptible to higher temperatures and poor water quality during strong wind events in the late dry season.

Snails - The CAM analysis for Pomacea canaliculata in the Mekong delta supported the hypothesis that climate change would enhance the invasiveness of the Golden Apple Snail. However, in comparison to Pila scutata, both would appear to be well adapted to cope with a hotter and drier dry season, and both able to take advantage of the increased rains and larger wetland area in the rainy season. From the above comparisons it may well be the habitat requirement for permanent wetland area that determines the populations of Pila. On the other hand, it may be that the higher reproductive capacity and voraciousness of the feeding habits of Pomacea drive its invasiveness, rather than climate change.

Water snakes - Unlike other reptiles e.g. turtles and crocodiles, the gender of water snakes is not dependent on environmental factors such as temperature. The rises in temperature are note expected to be so critical, but may encourage water snakes to aestivate more in the late dry season, which may make them more vulnerable to collection. The habitat changes induced by climate change are unlikely to affect the breeding of water snakes, although the populations are under severe pressure from hunting, which may increase as dependence upon other livelihood activities are threatened by climate change.

Turtles - Malaysian snail eating turtle and Yellow-headed temple turtle - The major climate change threat to turtles is increased temperature, especially during the period of

14 nesting and incubation of the eggs which takes place during the dry season, when temperatures are highest. Increased temperatures can affect the sex of the hatchlings and skew the sex ratios of populations, with greater numbers of females being produced at higher temperatures. There is little adaptive capacity available for turtles to adjust this. Also increased temperatures have been shown to affect behaviour of turtles, with slower swimming speeds and tendency to swim closer to the surface for those hatchlings incubated at higher temperatures. The lower rainfall and higher evapotranspiration in the dry season is likely to cause a shrinkage of the wetland habitats with smaller wetted areas and shallower pools making the turtles easier to catch, i.e increased vulnerability at this time. When the rains come and expand the wetted area again, the turtles are likely to benefit from the expanded area and higher availability of food sources.

Large water birds - The vulnerabilities of the large water birds, such as the storks, adjutants and Asian Open bill will be dependent upon the climatic conditions at the time of breeding and incubation, but this has not been considered since nesting occurs in the bird colonies at Prek Toal, rather than in Boeung Chhmar. However these birds are an important part of the ecosystem in Boeung Chhmar since they come in large numbers in March and April to feed taking advantage of the rich food sources to be found at Boeung Chhmar at the end of the dry season. The low water levels at that time of year make fish, snails and other aquatic animals easier to catch. It is important because the juvenile birds need this source of food to complete their growth to maturity. Thus the critical time for the ecological relationship between the large water birds and Boeung Chhmar will be at the end of the dry season. The most important factor is likely to be the impacts of climate change upon food availability at this time, and hence the populations of the food organisms. If these food sources decline in the future due to the influence of climate change, then the large water bird populations are likely to decline as well. (Milne, 2013)

The vulnerabilities of livelihood activities have been assessed based upon climate impacts upon the different natural resources on which they depend. The different fish resources have been considered, with black fish being less vulnerable to climate changes, except perhaps for the fish kills late in the dry season due to poor quality water released during strong winds. In the short term these fish kills represent a bonanza for the fishermen, but if they become a regular occurrence, they could affect fish populations and hence the local fishery, which would have serious implications for livelihoods of the communities around Boeung Chhmar.

White fish are more sensitive to poor water quality, but they will not be resident in Boeung Chhmar at this time of year. Other climate change threats elsewhere may affect the white fish, and climate change may alter breeding habitats which may influence fish populations.

Fish raising occurs in cages located underneath the houses. Caged fish are more vulnerable to extremes of temperature and poor water quality than fish in their native habitat, and outbreaks of disease can wipe out the stock very quickly.

Fishing supporting activities include fish processing and marketing, boat and engine maintenance, equipment supply etc. All small business are highly dependent upon the success of the fishermen. If fish stocks decline because of climate change, so will the fishing support livelihoods.

Water supply is a very significant issue for these communities, because although surrounded by water the quality of water in the immediate vicinity of the houses tends to be poor and not fit for drinking. Disposal of excreta and household wastes, excess fish food and fish excreta from cages cause poor quality conditions. It has been noted already that even such water used for bathing and washing can cause skin problems. With climate change the availability of good quality water for drinking will continue to be an issue, especially late in the dry season, and algal blooms increased by increasing temperatures may accentuate the skin disease problems.

The vulnerability of NTFP collection has considered Sesbania, rice field shrimps, snails, water snakes and turtles. In particular the combination of impacts of climate change with existing threats to water snakes and turtles make the collection of these wetland products especially vulnerable.

Ecotourism as a livelihood activity has not been developed, though visitors come for the bird watching in March to May. If large water bird populations visiting Boeung Chhmar decline, then the attractiveness of the location for tourists will also decline and activities such as home stay, guiding etc. will not develop.

Looking ahead to adaptation planning, some of the key features to manage and protect in Boeung Chhmar include ensuring adequate dry season flows of the Stung Staung and Stung Chikreng to maintain a positive inflow into the Ramsar site and especially into the open water areas; reducing the pressure on the gallery forests, through management of tree cutting, and replanting; reducing harvesting pressure on vulnerable groups such as the turtles and water snakes; managing the spread of alien species such as Mimosa pigra and Golden Apple Snail, and protection of predator species such as Open bill storks; provision of good quality drinking water for the communities.

1 Introduction

The Lower Mekong Basin (LMB) covers the four countries of Cambodia, Lao PDR, Thailand and Vietnam. It has a total area of 606,000 km2 and a population of more than 60 million people. The region is rich in natural resources, particularly forests, rivers and wetlands. These form important refuges for biodiversity and support the livelihoods of a large proportion of the LMB population, many of whom rely directly on natural resources. There are an increasing number of studies related to climate change and its potential impacts in the LMB, although these are largely focused on the regional level.

The LMB’s wetlands are vulnerable to changes in the transaction zone between aquatic and terrestrial environments, based upon their hydrological regimes and relatively low capacities for adaptation (Bates et al., 2008, and Bezuijen, 2011). A range of pressures caused by humans, including population pressure, overexploitation, infrastructure development, agricultural intensification, and mismanagement, affects the functions and services of wetlands. These already damaged systems are being further stressed by climate change. One aspect central to adaptation strategies for natural systems is thus to address the adaptation deficit (existing stresses that exacerbate climate change impacts) by increasing ecosystem resilience and rehabilitating ecosystem integrity. There is a need for analysis of these inter-linkages and an understanding of the implications of climate change to the health and function of the region’s wetlands.

Two sets of studies have to some extent filled the gap for specific ecosystems such as wetlands and these are:

 Mekong River Commission (2012) Wetlands of the Lower Mekong Basin – Basin- wide climate change impact and vulnerability Assessment. This included case studies of specific wetlands:  Cambodia – Stung Treng  Cambodia – Lower Stung Sen  Lao PDR – Siphandone  Lao PDR – Xe Champhone  Thailand – Lower Songkhram river basin  Thailand – Keang La Wa  Vietnam – Tram Chim  Vietnam – Mui Ca Mau  USAID’s Mekong Adaptation and Resilience to Climate Change (Mekong ARCC) (2013). This developed downscaled climate and hydrological modelling for assessing the vulnerability of different agricultural systems in selected priority provinces (Chiang Rai, Gia Lai, Kien Giang, Khammouane and Mondulkiri) of the four Lower Mekong countries, including:  Agriculture  Aquaculture and capture fisheries  Natural systems – NTFPs and Crop Wild Relatives in Protected Areas  Livestock  Socio-economics – focused on health and infrastructure

This study extends the climate vulnerability assessment of another wetland in Cambodia – the Boeung Chhmar Ramsar site within the Tonle Sap system. It draws upon the findings of the previous studies, especially the nearby core area of the Tonle Sap Biosphere reserve at Lower Stun Sen and the downscaled projections for climate change for Kampong Thom province used in the Mekong ARCC project.

The purpose of the study is to complement livelihood assessments carried out by IUCN in the communities around Boeung Chhmar as a part of the development of the management plan for the Ramsar site. As stated in the guidance for the preparation of case studies of climate change vulnerability of wetlands, the purpose of this assessment is:

“To identify the specific threats to the target wetland biodiversity, ecosystem services and livelihoods resulting from climate change and to develop a range of adaptation and management measures to ensure the continued existence of the wetland, its biodiversity and the ecosystem services that it provides.” （ICEM，2012）

The study has been funded through the Mekong Water Dialogues programme with funds from Ministry for Foreign Affairs of Finland.

2 Methods

The methods that have been used for assessing the vulnerability of the wetlands and wetland livelihoods to climate change guidance provided for the MRC’s case studies on climate change vulnerability of Mekong wetlands, the VCA analysis for community vulnerability, and the ICEM Climate Change Vulnerability Assessment and Adaptation (CAM). Climate change threat profiles for Kampong Thom province were taken from the USAID Mekong ARCC study.

2.1 Wetland and climate change case studies guidance

One of the products of the MRC’s basin-wide study of the impacts of climate change on wetlands was a manual providing guidance for wetland case studies （ICEM，2012）. This manual suggested nine steps for conducting such wetland climate change assessments:

1. Reviewing institutional and policy frameworks at the local and national level for those elements which influence management and use of the site 2. Describing the main biodiversity and ecosystem service characteristics of the site, their status and the ways they contribute to livelihoods. 3. Define the main features which determine the wetland type/category 4. Document the nature and impact of past climate extremes on the wetland and the “adaptation” responses by communities, government and others. 5. Assess the impact of projected climate change threats on the key “assets” of the wetland 6. Document the other development threats to the wetlands and the main drivers of change 7. Define the adaptation options and their phasing to maintain and enhance the wetland’s natural systems and services 8. If resources permit, value the impact of climate change on wetlands if not action is taken and the cost of adaptation 9. Define a road map for implementing an adaptation plan for the wetland

These steps together with component aspects to be studied are shown in Figure 2.1.

This study focused on steps 2 – 6 and left the adaptation and management steps, and wetland valuation for further follow-up development. Of particular use for this study was the guidance provided in the manual for carrying out the assessments for:

 Wetland hydrology field survey checklist  Wetland habitat and biodiversity vulnerability  Wetland ecosystem services trend analysis  Wetland livelihood vulnerability.

Figure 2.1 Nine steps approach for wetland and climate change case studies

Source: ICEM 2012

2.2 VCA

The design of the VCA as participatory tools were used aiming to capture seasonality of climate and non-climate impacts, the vulnerability of major livelihoods, natural resources and land use; historical trajectories of extreme climatic events and how people could manage to mitigate their impacts; and internal strengths/weakness and external opportunities and threats towards climate and human made stressors.

2.3 Climate Change Adaptation and Mitigation Methodology (CAM)

The ICEM Climate Change Vulnerability Assessment and Adaptation (CAM) is an integrated approach to climate change mitigation and adaptation planning developed by ICEM. The methodology has and continues to be developed and adapted to project and case specific needs. CAM is an overall conceptual approach that has been designed to integrate a wide range of tools and processes that can be applied at different levels and stages of climate change mitigation and adaptation planning. This description of the CAM process is taken from USAID Mekong ARCC Main report. （ICEM，2013）

Figure 2.2 Vulnerability assessment and adaptation process

Figure 2.2 to Figure 2.4 summarize the CAM process steps and concepts. It has three main phases — vulnerability assessment, adaptation planning, and then adaptation implementation (Figure 2.2). This study has gone only part way along the adaptation process, focusing on the first phase of identifying impacts and assessing vulnerability for Boeung Chhmar habitats and species of relevance for livelihoods (Figure 2.3).

Figure 2.3 Climate change impact and vulnerability assessment process

The vulnerability assessment follows a recognized pattern of assessing the exposure and sensitivities to the climate change threats, and the likely impacts that may result. When combined with the adaptive capacity of the species or system, a ranking and analysis of their vulnerability can be made.

Figure 2.2, Figure 2.3 and Figure 2.4 are conceptual in nature. For their practical application, a precise step-wise process is defined and supported by a tool box which facilitates appropriate information inputs at each step. The operational vulnerability assessment and adaptation planning process involves six main components:

1. Determining the scope, by identifying the geographic and sector focus of the assessment and the species and systems (natural, social, economic, institutional, and built) which will be impacted. 2. Determining the climate change threats through an analysis of past extreme events and trends and through climate modelling and downscaling of future climate and hydrology against various scenarios. The definition of projected climate change threats is part of the baseline—it needs to be fine-tuned to the specific sensitivities of the species and areas under focus in the form of threat profiles. 3. Conducting a baseline assessment to describe the past and existing situation, trends and drivers across each of the identified systems, and projecting the changes to these systems which will occur irrespective of climate change. The baseline involved the review of scientific, socio-economic and development literature, existing databases, consultation with other experts, and team expert judgment. The theme baseline assessments are provided in the separate theme volumes prepared for this study and include:

• Identification of key species/systems, • Description of key species/systems, • A species/systems database including climate tolerances, • Description of impacts of past extreme events, 4. Conducting the impact assessment: For each of the target species and systems, the exposure, sensitivity, impact, and adaptive capacity were defined using the baseline and climate threat modelling results and matrix support tools developed by ICEM. The theme vulnerability assessments are summarized in the separate theme volumes to this report.

The CAM method outlines four important factors in assessing vulnerability of the target species and systems to the defined climate change threats: exposure, sensitivity, impact, and adaptive capacity and provides a set of tools to facilitate assessments at each stage (Figure 2.4).

 Exposure is the degree of climate stress on a particular system or species; it is influenced by long-term changes in climate conditions, and by changes in climate variability, including the magnitude and frequency of extreme events.  Sensitivity is the degree to which a species or system will be affected by, or responsive to climate change exposure.  The potential impact (or level of risk) is a function of the level of exposure to climate change-induced threats, and the sensitivity of the target assets or system to that exposure.  Adaptive capacity is understood in terms of the ability to prepare for a future threat and in the process increase resilience and the ability to recover from the impact. Determinants of adaptive capacity include:  Natural systems • Species diversity and integrity • Species and habitat tolerance levels • Availability of alternative habitat • Ability to regenerate or spatially shift • For individual species: dispersal range and life strategy  Infrastructure • Availability of physical resources (e.g., materials and equipment) • Backup systems (e.g., a plan B)  Social factors • Social networks • Insurance and financial resources • Access to external services (medical, finance, markets, disaster response, etc.) • Access to alternative products and services  Crosscutting factors • The range of available adaptation technologies, planning, and management tools • Availability and distribution of financial resources • Availability of relevant skills and knowledge • Management, maintenance, and response systems including policies, structures, technical staff, and budgets

• Political will and policy commitment

Figure 2.4 Parameters and issues considered in the baseline and vulnerability assessment process

When impact and adaptation capacity are considered, a measure of relative vulnerability can be defined.

The CAM method can use numerical scoring for exposure, sensitivity, impact, and adaptive capacity leading to a comparative score for vulnerability, or it can use qualitative terms from very low to very high with the aid of assessment tools which come with the method. Table 2-1 and Table 2-2 show the scoring matrices used in this study to assess impact and vulnerability.

Table 2-1 Determining impact – Exposure X Sensitivity (Source: ICEM)

Table 2-2 Determining vulnerability – Impact / Adaptive capacity (Source: ICEM)

2.4 Determining ecological response to climate change

In 2008, IUCN Species Programme（Foden，2008）produced a paper on species susceptibility to climate change in which the effects on different species could be associated with different predicted changes. A linkage diagram from that report is presented in Figure 2.5 and demonstrates the complex relationship between climatic factors and biotic response. This was used in the manual for rapid climate change assessments for wetland biodiversity in the Lower Mekong Basin. （ICEM，2012） It identifies some of the impacts that can be expected on wetland biodiversity in the Lower Mekong Basin.

The methods for determining the ecological response of habitats and species to climate change depend upon knowledge of the biological requirements for temperature and water availability / water level at different stages of the lifecycle of species, or in the year for habitats. Whilst complex ecological models may be available, at this level of analysis it is necessary base the vulnerability assessment upon scientific judgment, based upon information from published papers on the biology and behavior of the habitats or species, their tolerances to temperature and drought etc. and local knowledge about these issues. It is important to identify key life stages where the organism is likely to be less tolerant, e.g. during breeding and juvenile development; flowering, fruiting and seed dispersal. It may also be important to note the critical times of year when the organism is hibernating or sheltered from climate extremes, e.g. eels in their burrows. Other factors may include availability of

25 food sources, or the resistance to parasites and diseases that may be reduced by climate change.

Figure 2.5 Summary of some of the predicted aspects of climate change and examples of the effects that these are likely to have on species (Source: Foden 2008)

2.4.1 Comfort zones

Comfort zones are where species and ecosystems experience the most suitable growing conditions in terms of the range and timing of temperature and rainfall. They are defined to include 50% of the baseline variability around the mean in temperature and rainfall for typical months, seasons and years.

All species have a range of climate in which they grow most comfortably. For agricultural crops usually that range is well understood—climate parameters have been studied in detail and published widely. For example, it has been shown that maize grows well in areas that have a total annual precipitation of between 500 and 5,000 mm and mean maximum temperature in the range of 26°C to 29°C. Outside this range the growth of the plant is constrained or inhibited entirely. For wild species and habitats, the comfort range is poorly

26 researched and documented, even if known anecdotally by local communities and managers.

Comfort zone analysis requires information on the range of rainfall and temperature that was experienced during 50% of the historical baseline around the mean. For example, Figure 2.6 shows the wet season and dry season daily maximum temperature comfort zone for the Kampong Thom. In this area the ecosystem is adapted to and comfortable within a daily maximum temperature of between 27°C and 29°C during the wet season and 28°C and 32°C during the dry season. By 2050 the daily maximum temperature during the wet season will shift completely outside the baseline comfort zone — the dry season temperature will not shift as dramatically although the habitat will still become stressed. The comfort zone analysis enables the researchers to make rapid assessments on the relative impact of climate change on species and habitats.

Figure 2.6 Maximum temperature comfort zone analysis of temperature range shifts in wet and dry season, Kampong Thom Province

Source: （ICEM，2013）

3 Description of Boeung Chhmar

Boeung Chhmar is one of three Core areas of the Tonle Sap Biosphere Reserve. It is located just north east of the main constriction in the Tonle Sap Great Lake as shown in Figure 3.1. The other two Core areas are at Prek Toal in the north west corner of the lake and Lower Stung Sen at the bottom end of the lake.

Figure 3.1 Overview map of the Tonle Sap with major land use/land cover classes from JICA (1999) below 15 m asl and water depth measurements

Boeung Chhmar Ramsar site

Source: （Arias，2012）

The wetland lies within Kampong Thom province and is about 70 km west of the provincial capital. Access to Boeung Chhmar, however, is easiest by boat across the Tonle Sap Great Lake from Kampong Luang commune on the southern shore of the lake.

The Ramsar site of Boeung Chhmar and associated river system and floodplain was designated in 1999 and covers a total area of 28,000 ha of which 23,000 lies in Kampong Thom Province and 5,000 ha in Siem Reap province. This is shown in Figure 3.2. The maximum elevation of the site is 10 m above sea level. The site consists of a permanent open water body of about 3,803 ha, surrounded by a complex creek system and flood plains, with flooded forest fringing the shores of the Tonle Sap and parts of the open water lake. The hydrology of the site is largely determined by two rivers the Stung Staung and Stung Chikreng and the interaction with the adjacent Tonle Sap Great Lake. The creek systems are

28 mostly shallow especially in April with a maximum depth of about 2 m. The lake is shallower at 0.5 to 1 m deep. During inundation the lake reaches a maximum depth of 4 m.

The area contains a range of complex wetland habitats including seasonally inundated forest, forest mosaic and wood and bushlands. The nutrient dynamics of the area creates a rich ecological diversity with threatened species such as the globally threatened Greater Adjutant Leptoptilus dubius, Fishing cat, Prionailurus viverrinus and Hairy nose otter, Lutra sumatrana. It is also an important breeding area for molluscs which provide the feed sources for large water birds and migratory bird species.

Figure 3.2 Map of Boeung Chhmar Ramsar site

Source: Ramsar

The Ramsar designation was based upon several criteria:

 Criterion 1: It is a good example of near natural wetlands in the Mekong river Ecoregion, and associated with the Tonle Sap, the largest lake in south east Asia.  Criterion 2: It supports a large assemblage of plant species, fish, reptile, mammal and water bird species, many of which are vulnerable or endangered.  Criterion 5: It regularly supports more than 20,000 individuals of large water birds, being one of main feeding grounds for the breeding colonies of birds at Prek Toal, such as Asian Open-bill, Oriental Darter, Spot billed Pelican, Indian Cormorant, Lesser Adjutant and Greater Adjutant. It is considered to hold at least 1% of a biogeographic population of congregatory water bird species.

 Criterion 8: There are 296 species in the Tonle Sap (43% grey fish, 40% white fish and 17% black fish species) and around 17 are considered to be threatened species. When inundated the Boeung Chhmar site provides a rich habitat for fish living, breeding and feeding.

3.1 Hydrological characteristics

3.1.1 The Tonle Sap system

The hydrological regime of the Boeung Chhmar, part of the Tonle Sap Lake ecosystem, is strongly influenced by the exchange of water between the Mekong River and Tonle Sap Lake, along the Tonle Sap River, and two relatively small rivers1 – the Stung Staung and Stung Chikreng. To a lesser extent, it is also affected by the wider Tonle Sap catchment.

In the dry season, the Tonle Sap Lake covers an area of 2500 km2 with a maximum depth of about 1m, as the lake drains into the Mekong River through the Tonle Sap River. However, when the Mekong floodwaters approach a peak in July-August, the flow of the Tonle Sap River is reversed. The volume of the lake increases from about 1.3 km3 to 50-80 km3, depending on the flood intensity, and its surface area increases to 10,000-15,000 km2 (Kummu et al, 2003). The depth of the Tonle Sap increases to 8 – 10 m. Extensive flooding in the Tonle Sap floodplain lasts about five months.

For the lake overall, 57% of the water comes from the Mekong River in the wet season. During an average wet season, about 52% of this water comes in directly through the Tonle Sap River, and 5% flows overland through the floodplain from the Mekong. Another 30% comes from tributaries including the Stung Staung and Stung Chikreng Rivers, and about 13% comes as direct rainfall over the lake itself (Kummu and Sarkkula, 2008). The reverse Mekong flow phenomenon results in peak water levels in Tonle Sap lagging 1-2 months behind the peak of seasonal rainfall.

Floodwaters begin to recede in the early dry season in November, with the lowest water levels occurring at the end of the dry season in early May (Scott 1989). The Mekong River yields approximately 51% of this inflow of water, but is responsible for the majority (ca.75%) of the sediment deposited in the Tonle Sap Lake (Kummu et al. in press a). It is estimated that more than 80 % of the sediment the Tonle Sap system receives from the Mekong River and its tributaries is stored in the lake and its floodplain. The dynamic nature of sediment movement into and out of Tonle Sap has been the subject of much speculation, i.e. that the lake is rapidly filling up with sediment due increasing sediment loads coming from its catchment.

However, recent studies have shown that net sediment accumulation within the Tonle Sap Lake itself is low, and not accelerating with respect to the long-term sediment dynamics of the system (Kummu et al. 2005). The majority of the sediments settle in the inundated forest and shrubland areas of the floodplain (Sarkulla et al. 2003).

1 Relatively small compared to the Stung Sen which flows through Kampong Thom. Stung Staung and Stung Chikreng have catchment areas of 4,357 km2 and 2,714 km2 respectively compared to the Stung Sen, which has a catchment area of 16,360 km2. The total catchment area of the Tonle Sap is 85,851 km2 of which the lake itself is only 2,744 km2.

3.1.2 Boeung Chhmar

Although it is directly connected with the main lake of the Tonle Sap, Boeung Chhmar has its own distinct hydrological character. The main hydrological features are the two inflowing rivers, the Stung Staung and Stung Chikreng, which determine the water levels in the Boeung Tonle Chhmar. The Stung Staung flows directly into the lake through a complex of channels at the north end and flows out again principally through a channel at the south east and south west corners of the lake. The Stung Chikreng flows into the complex of channels and smaller bodies of open water to the west of the main Boeung Tonle Chhmar; some of the flow from the Stung Chikreng may reach the lake from creeks in the south west part, but most will flow through a complex of creeks into the Tonle Sap directly.

The Boeung Tonle Chhmar is a natural depression perched slightly higher than the main Tonle Sap, and so it maintains its water levels even as the waters in the Tonle Sap recede. The creeks flowing into and out of the lake cut through the seasonally inundated floodplains, grasslands and shrublands, with the gallery forests mainly occurring on the outer shoreline of the Tonle Sap.

Figure 3.3 Satellite imagery of Boueng Chhmar, showing bodies of open water and

creek system

In the first part of the wet season the water levels in the Boueng Tonle Chhmar and the other bodies of open water are raised by the two rivers and local rainfall. Later in the wet season the water levels in the lake will receive water from the Tonle Sap Great Lake as it starts to rise first due to the inflow from its tributaries and then in July-August due the back flow from the Mekong. Thus like the larger lake, the Boeung Tonle Chhmar is subject to three types of inflow:

 Throughout the dry season and in early wet season – Stung Staung and Stung Chikreng. In the low water season, a large part of the area around Boeung Chhmar

dry out, with water remaining only in the open water bodies, other scattered pools and watercourses.  Mid wet season – from rising water levels in the Tonle Sap Great Lake from its tributaries and local rainfall  Late wet season – from back flows from the Mekong raising the overall levels of water in the Tonle Sap Great Lake.

In the wet season, the wetland area is completely flooded, with only the tops of emergent trees remaining above water. Changes in water levels not only bring about variation in the wet surface of the lake and the floodplain but also influence the exchange between groundwater and surface water. When the floodplains are inundated various key processes occur simultaneously that drive diurnal and seasonal limnological changes (Lamberts, 2008), particularly the wet and dry cycle that produces nutrients through the decomposition of leaf fall in the ponded waters and their release into the flood waters. The presence of the flooded forest and creek system plays a large part in trapping the sediments flowing in from the two rivers, and to maintaining the fertility of the ecosystem. The flooded forests and shrublands also serve to protect the open bodies of water in Boeung Chhmar from the extremes of the weather, back flow and sediments in the Great Lake during the late wet season.

In recent years, abstraction of irrigation water from the Stung Staung and Stung Chikreng has almost stopped the flow of water reaching Boeung Chhmar during the dry season and early wet season. There are concerns that this shortage of the natural inflow during the dry season is changing the hydrology and ecology of the wetland.

3.2 Habitats – area and extent

The wetland habitats that have developed in the Boeung Chhmar area are highly dependent upon the varying water levels and lengths of inundation. This is clearly illustrated in Figure 3.4. Which shows the cross sectional profiles in the late wet season when the water levels are highest and in the late dry season when the levels are lowest. The species that survive these conditions are highly adapted, and there is a clear zonation of species dependent upon the elevation, i.e. the length of time that the plants can withstand inundation. This is shown in Figure 3.5 which identifies four groups of plants – upper shrublands which survive the least inundation, short tree forest, gallery forest and aquatics.

Figure 3.4 Cross section of floodplain habitats in Kampong Thom province during a) October/November and b) May/June

Source: （Davidson，2006） quoting （Balzer，2002）

Figure 3.5 Vertical distribution of dominant plant species in the Tonle Sap floodplain (to 6 m elevation)

Source: （Davidson，2006） quoting （Hellsten，2003）

The major habitats are the lake's open water and the vast inundated floodplain. Most of the plain can be classified as "seasonal freshwater swamp savannah" (revised IUCN classification developed in April 1993 with Mekong Secretariat). Trees such as Barringtonia acutangula and Xanthophyllum glaucum are very common along the levees of waterways within the floodplain and as scattered groves on the floodplain. In the Boeng Chhmar region of the flood plain there are numerous creeks, and over the floodplain area there are scattered pools, some of which in the dry season appear to contain blackwater due to the release of humic acid from decaying vegetation. There are thus three main habitats found in Boeung Chhmar:

1. The Lake and river systems – open water. Common species include:  Non-rooted floating plants: the water hyacinth Eichhornia crassipes is the dominant non-rooted floating plant. Pistia stratiodes and Salvinia sp. are present in similar quantities. (Both Eichhornia and Salvinia are introduced species)  Non-rooted, submerged plants: Utricularia sp. is present in small amounts.  Rooted, submerged macrophytes are generally absent due to the turbidity of the water.  Rooted, floating leaved: Trapa natans, Nymphaea sp.  Creeping: Ipomea reptans and Ludwigia adscendens.

2. The River and Creek Levees - These are normally the highest parts of the floodplain and trees such as Barringtonia acutangula and Xanthophyllum glaucum are very common. Saplings of B. actangulata are common, which must survive at least 4 months of complete inundation. This is a medium sized evergreen tree with traditional medicinal uses and a valued timber species.

3. The Floodplain and Backwater Swamp - The backswamp areas are lower than the levees. In the dry season the water table may still be at the surface of the soil (+/-10cm). The dominant plant forms are extensive thickets of the shrub Sesbania javanica and "meadows" of the low-growing Polygonum barbatum. Ipomea reptans is common creeping over the ground and there are extensive areas of water hyacinth still growing in the moist soil.

The areas of the different habitats within the Boeung Chhmar Ramsar site have been estimated from satellite imagery for this study and are as follows:

Habitat type Estimated area – ha Percentage

Open water lake 3,803 14%

Open water – rivers and creeks 4,722 17%

Flooded forest 644 2%

Short-tree shrubland 16,090 57%

Floodplain – seasonally inundated grassland 2,749 10%

Figure 3.6 Map of key habitats in Boeung Chhmar Ramsar Site

3.3 Seasonal ecological processes

In the paper, The Biodiversity of the Tonle Sap Biosphere Reserve, Davidson (2006) describes the ecological processes by season according to the different habitat zones (Table 3-1). This is an extremely useful framework for assessing the impacts of seasonal shifts due to climate change.

Table 3-1 Seasonal calendar of different physical and ecological process in the Tonle Sap

Season Month(s) Key Physical, Land- and Human- Ecological Processes/Events by Habitat Type use Processes Open Lake Swamp forests Short-tree shrublands Grasslands/agro-ecosystems Reversal of Tonle Sap River flow In-migration of "white fish" Out-migration of terrestrial Tree and shrub flowering Tree and shrub flowering into Tonle Sap Lake - floodpulse from Mekong via Tonle Sap breeding species (grassland birds and fruit production and fruit production begins River and larger mammals) as flood rises In-migration of "white In-migration of "white fish" In-migration of post-breeding large Deepwater rice crops fish" for feeding, nesting for feeding, nesting and waterbird congregations (storks, germinating in outer floodplain and spawning spawning ibises, herons and egrets, pelicans) Early Lateral migrations of Lateral migrations of "black In-migration of wet-season May-July monsoon Watersnake harvest begins "black fish" to nesting fish" to nesting and breeding waterbirds (e.g. rails, and spawning habitats spawning habitats crakes, bitterns) Departure of large In-migrations of some black and waterbird breeding white fish species for nesting, colonies (storks, pelicans, spawning and juvenile growth. ibises, herons and egrets)

Expansion of Tonle Sap Lake to max. inundation through reverse Tree and shrub flowering Tree and shrub flowering flow mechanism and catchment and fruit production and fruit production rainfall Deciduous tree leaf fall Deciduous tree leaf fall Largest sediment inputs (underwater) (underwater) Fishing (outside lot system) in Fish nesting, spawning, Fish nesting, spawning, August- Fish nesting, spawning, feeding and Mid-monsoon outer floodplain agro- feeding and juvenile feeding and juvenile growth October juvenile growth period ecosystems growth period period Cormorants and Darters Main phase of deepwater rice Deepwater rice crop main return to nest colonies growth in the outer floodplain agro- growth phase and commence breeding ecosystems Fish perform function of natural Watersnake breeding Watersnake harvest peaks Watersnake breeding period pest regulators in traditional rice period agricultural systems

Flood water begins to recede as Mekong River level drops and Out-migration of "white fish" Leaf flush in all deciduous Leaf flush in all deciduous Continued growth of "floating Tonle Sap River reverses flow to Mekong River via Tonle Sap and evergreen tree and evergreen tree species grasses" again and begins draining the River and floodplains species October- lake Late monsoon November Large-scale commercial fishing begins in all fishing lots and main Watersnake breeding Watersnake breeding period waterways draining Tonle Sap period lake Deepwater rice ripening phase

Large-scale commercial fishing Out-migration of "white fish" In-migration of terrestrial breeding Cormorants and Darters continues in all fishing lots and to Mekong River via Tonle Sap species begins (grassland birds complete breeding and main waterways draining Tonle River and floodplains including Bengal Florican) as land fledge Sap lake continues reexposed on flood recession Large waterbirds (storks, Large in-migration of Palearctic November- Early dry Flood waters recede increasingly Large feeding aggregations of ibises, pelicans, herons "winter visitor" bird populations January rapidly terns and gulls and egrets) return to (raptors, chats, hirundines, nesting colonies warblers, pipits, wagtails) Second watersnake harvest peak Deepwater rice harvest

Large-scale commercial fishing Main breeding period for ?Concentration of black fish Main breeding period for terrestrial begins in all fishing lots and main large waterbrids (storks, as surrounding floodplain grassland birds (e.g.Bengal Florican, waterways draining Tonle Sap ibises, pelicans, herons dries out quails and buttonquails) lake and egrets) Black fish concentrated in Increasingly drought like High concentrations of Black fish concentrated in Large feeding aggregations of remaining waterbodies and conditions develop in outer fish behind fish traps in remaining waterbodies and terns and gulls performing "overland" floodplain fishing lots performing "overland" migrations migrations Mid-late dry January-May Estimated main breeding Estimated main breeding Local movements of Palearctic birds Extensive burning of grassland period for turtles and period for turtles and in response to availability of key and shrubland pythons pythons food resources Domestic livestock may partly fulfil Livestock grazing (January-early grazing function of extirpated April) herbivore populations Preparation of land for deepwater rice cultivation

(Source: Davidson 2006)

3.4 Key species

3.4.1 Fish

The fish in the Mekong are generally categorized into three main groups2:

 Black fish - Black fish are chiefly residents in the Tonle Sap. The waters they inhabit are tea-coloured by chemicals dissolved from floodplain vegetation, the decomposition of which increases acidity and depletes oxygen, stresses to which black fish are adapted (Hortle et al. 2004). Most species are specifically adapted to such conditions, and can breathe air, are able to move overland in search of fresh waterbodies, and some can survive out of water for long periods (Hortle et al. 2004). Black fish are mostly carnivorous and detritus feeders, and include the Channidae (Snakeheads), Clariidae, Bagridae (Mystus spp.) and Anabantidae (Baran 2004).

 Grey Fish or opportunists - Opportunists are small, fast-growing species, able to make maximum use of the flood period for prolific reproduction and/or growth. This group (which are also classified as white fish by some authors) comprises mainly cyprinids (e.g. Henicorhynchus siamensis, Thynnichthys thynnoides, Dangila spilopleura), which are harvested in large quantities for the manufacture of prahoc, fish sauce and feed for caged fish. “Trey Riel” Henicorhynchus spp. are the most common and account for the largest catch by weight of any genera in Cambodia (van Zalinge et al. 2000).

 White fish - White fish are mainly associated with the main channels and streams, and exhibit strong lateral and longitudinal migrations, including into floodplains. They move into the Tonle Sap as the flood rises in the early wet season (from May), remaining there to feed and reproduce, until the waters begin to recede (from November), when they return to the turbid (“white”) waters of the Tonle Sap and Mekong Rivers, where they spend the majority of each annual cycle (e.g. Nao 1997, Hortle et al. 2004). The white fish includes many cyprinids (Cirrhinus microlepis, Hampala macrolepidota, Barbodes altus, Leptobarbus hoeveni, Osteochilus melanopleura, Morulius chrysophekadion), various Pangasius sp., Siluridae (e.g. Wallago attu, Micronema apogon) and Notopteridae (e.g. Notopterus chitala and N. notopterus) (Baran 2004).

 Eels – There is one species of true eel (Anguilla marmorata) and two species of swamp eel (Synbranchidae) (Mastacembelus armatus and Monopterus albus) found in the Tonle Sap ecosystem. They are separated out here because of their seasonal dormancy behavior and importance as a fishery in Boeung Chhmar. Adults inhabit streams, ponds, canals, drains, rice fields, both clear and turbid water. They are nocturnal and carnivorous. They are facultative air-breathers. At the start of the dry season when there's a decline in water level, it digs a tubular burrow in a bank or on the bottom. This burrow, which is for the most part sub-horizontal, can have several diverticula, followed by a vertical section which leads to the exterior by only one opening. Although breathing is slowed down, the fish remains active and flees if it is

2 Fish group descriptions quoted from （Davidson，2006）

disturbed. They emerge from their burrows at the beginning of the wet season as the water level starts to rise.

The fish species of conservation concern occurring in the Ramsar site are listed in Table 3-2.

Table 3-2 Fish species of conservation concern in the Boeung Chhmar Ramsar site

3.4.2 Invertebrates

Molluscs

The Mekong Basin, including in the Tonle Sap, exhibits an extremely high diversity of molluscs (snails and mussels) (Rainboth 1996). Twenty-nine species of mollusc (comprising over 50% of all species present) were identified in the zoobenthos of “the Mekong, the Tonle Sap channel and the floodplains”, and made up 85% of the zoobenthos by weight (Nguyen and Nguyen 1991 cited in Lamberts 2001). One species of ampullarid snail, probably in the genus Pila, was found in the ricefield ecosystem in Kampong Thom (Balzer et al. 2002).

Pila scutata is one of common molluscs collected in Boeung Chhmar. According to the IUCN Redlist, it is of Least Concern. The species is found in calm freshwater habitats, such as paddy fields, ponds, pools and slow moving streams. They usually climb on the aquatic grass/plants by their feet. It is amphibious. It can aestivate and tolerates drying out.

Pomacea gigas (Apple Snail), which feeds on the growing basal stems of aquatic plants, has had a major impact on aquatic habitats and agro-ecosystems throughout south-east Asia, degrading natural vegetation and severely reducing rice yields (Round 2002, Welcomme and Vidayathon 2003). Affected habitats become denuded of their fish populations, and the introduced snails compete with native species such as Pila spp., which specialize in feeding on already moribund plants.

It is a favoured prey of Asian Openbill, the population of which has increased rapidly in Thailand’s central plains potentially as a result of the abundance of P. gigas (Round 2002). Toxic agro-chemicals are used to eradicate the snail, which can then accumulate in species higher up the food chain. The case of the apple snail is an example of the disastrous consequences that can follow from an inappropriate introduction (Welcomme and Vidayathon 2003).

Crustacea

At least one crab, and one shrimp species occurs in ricefield habitats in Kompong Thom (Balzer et al. 2002). Five morphologically distinct forms of crab are distinguishable in these ricefield agro-ecosystems (all but one of which is abundant), indicating as many as five species may occur; van Amerongen (1999 cited in Balzer et al. 2002) suggests that all ricefield crabs in the Tonle Sap belong to the genus Somanniathelphusa. Somanniathelphusa crabs are generally considered rice pests (Balzer et al. 2002), and as such are collected from June to December, but only eaten in times of food scarcity.

The shrimp species, identified as Macrobrachium lanchesteri (Mogensen in Balzer et al. 2002), is abundant between September and December, when it is harvested for food. C. (M). lanchesteri is a relatively small species but one which may make a considerable contribution to the biomass of the habitat in which it lives since it normally occurs in large numbers. Though it is of rather small size, it is larger than many other prawns which are of economic importance. Moreover it occurs in large numbers and can attain a larger size under specially favourable conditions. The species appears to be indigenous to the swamps and ricelands of southeast Asia (Johnson, 1968).

3.4.3 Large water birds

Birds have been more extensively studied than any other group, 210 species have been recorded within the wider Tonle Sap. More than 25 species of globally and/or Asia regionally significant populations, 17 of which are IUCN Red-Listed. These most significant species and populations are:

 Globally significant colonies of Greater and Lesser Adjutants, Spot-billed Pelican, Painted and Milky Storks, Black-headed Ibis, Darter and Indian Cormorant that breed in seasonally inundated swamp forest in the Prek Toal Core Area;  Probably one of the largest known breeding populations of Grey-headed Fish Eagle;  A unique bird community in perhaps the largest remnant tract of seasonally inundated grasslands and agro-ecosystems in South-east Asia, including during the dry season, probably the world’s largest breeding population of Bengal Florican, the largest known wintering population of Manchurian Reed Warbler, very small numbers of White-shouldered Ibis and Asia-regionally important populations of Greater Spotted and Imperial Eagles, and in the wet season post-breeding aggregations of Greater and Lesser Adjutants and Black-headed Ibis.

Residents

Oriental Darter, Cormorants and Asian openbill are known as the resident waterbirds in Boeung Chhmar Ramsar Site. In 2000 around 7 nests of darters and cormorants were found in the core area and a large mixed colony at Moat Khla (R.v.Zalinge, T.Evans & S.Visal Oct 2008). According to the local people there were some darter’s colony found at northern part close to Boeung Chhmar open lake, but they were chased away by the fishing lots guards. Asian openbill species are also found in small number in a whole year round in Boeung Chhmar Ramsar Site. The distribution and seasonal movements, after nesting at Prek Toal from September to January, the three species are found in Boeung Chhmar Ramsar Site from mid January to July (with peak numbers during March to May when the water levels in Boeung Chhmar become lower).

Visitors

The visitor species include Painted Stork, Lesser and Greater Adjutant, and Spot–billed Pelican. The distribution and seasonal movements show that, after nesting at Prek Toal from September to January, these species are found in Boeung Chhmar Ramsar Site from mid- January to July. Peak numbers occur during March to May when the water level in Boeung Chhmar becomes lower, and with greater availability of food sources.

Table 3-3 Waterbird species of conservation concern in Boeung Chhmar Ramsar site

3.4.4 Mammals

Relatively few mammal species occur in the TSBR for a tropical lowland ecosystem. These include six IUCN Red Listed species, each of which inhabits the seasonally inundated swamp forests and short-tree shrublands. Populations that are potentially of global or regional conservation significance are:

 Long-tailed Macaque (widespread and locally common, probably one of the larger populations in South-east Asia)  Germain’s Silver Leaf Monkey (poorly known but certainly important globally)  Smooth and Hairy-nosed Otters (both poorly known but potentially important in South-east Asia)  Fishing Cat (very poorly known but potentially important in South-east Asia)

3.4.5 Reptiles

There are 23 reptile species, of which three species of Python are of conservation importance – Blood python (Python curtus), Rock python (P. melurus bivittatus) and Reticulated python (P. reticulatus). The Boeung Chhma Core Area is reportedly an important area for both Burmese and Reticulated Pythons (Long 2003). Pythons are hunted heavily in both areas (Long 2003), for their skins, meat and blood to serve both domestic and international markets. Female pythons make their nests within dense scrub, on the ground, during the dry season, typically laying 20-30 eggs.

Water snakes

The abundance of reptiles within the TSBR is perhaps best illustrated by what is the largest exploitation of any single snake assemblage in the world (Stuart et al. 2000): an estimated 3.8 million snakes were harvested between June 2004 and January 2005 (Brooks et al. 2005). This harvest principally targets species in the sub-family Homalopsinae (Homalopsine watersnakes).

 The rainbow Watersnake E. enhydris is the most abundant species caught, accounting for 72-ca.80% of the number of individuals in the overall catch (Stuart et al. 2000, Brooks et al. 2005).  The Tonle Sap Watersnake E. longicauda is the second-most abundant species, and accounts for almost 50% of the total caught in the southern TSBR (Brooks et al. 2005). This poorly known species is endemic to the Tonle Sap Lake and River, and is Cambodia’s only known endemic reptile.  Other species targeted include Puff-faced Watersnake Homalopsis buccata and Bocourt’s Watersnake Enhydris bocourti, both of which have been collected over several decades for their skins, which are exported to Thailand, Vietnam and China (Stuart et al. 2000, Long 2003, Brookes et al. 2005). The Bocourt's water snake is also traded alive for its meat, supplying restaurants locally and regionally. Long (2003) considers Bocourt’s Watersnake to be locally rare as a result of overexploitation.  Other species that occur in the harvest include Cylindrophios ruffus, Xenochrophis piscator, Erpeton tentaculatum, Enhydris plumbea, Enhydris subtaeniata, Boiga occellata, Boiga cyanea, Naja spp. and Ptyas korros.

The enormous scale of this snake harvest is a very recent phenomenon. Since the late- 1990s, snakes have become one of the main protein sources for captive-bred crocodiles in the burgeoning number of crocodile farms around the lake. In addition to the species also targeted for their skins, a proportion of the catch of several species is also used for human consumption (Stuart et al. 2000, Brooks et al. 2005).

Breeding in the snakes appears to take place during September, when eggs are seen and harvested.

Turtles

Turtle populations in lowland wetland habitats throughout Cambodia have plummeted as a result of over-harvesting, chiefly for both legal and illegal export to China and Vietnam, for use in traditional medicine and as food (e.g. Walston 2005), and also for domestic consumption (Touch et al. 2000). The TSBR is no exception: turtles here have sustained heavy harvesting pressure since the early 1980s (Keng 2000, 2003). Most recent turtle records derive from markets and captive individuals, few of which have verifiable locality data. Eight species are reported or known to occur in the TSBR, all of which are globally threatened; the most commonly found species in the Tonle Sap include:

 Asian Box Turtle Cuora amboinensis IUCN Vulnerable Considered to be the second most numerous turtle in the TSBR after Malayemys subtrijuga, but it is now considered uncommon in the TSBR, which is considered to support a small population, and becoming harder to find in the wild (Long 2003). This turtle occurs in lowlands throughout Cambodia, and its global range extends from north-east India to the Philippines and Indonesia (Stuart et al. 2001).  Black Marsh Turtle Siebenrockiella crassicollis IUCN Vulnerable This species tends to occur more commonly in floodplain ponds away from the Great Lake itself, where it is considered rare, but is not favoured for its meat, which is considered by many to be either foul-smelling or even inedible (Holloway et al. 2000).  Yellow-headed Temple Turtle Hieremys annandalii IUCN Endangered. Considered the third most common species in the TSBR.  Giant Asian Pond Turtle Heosemys grandis IUCN Vulnerable. Reported from the TSBR within Kompong Chhnang province (under the name Orange-headed Temple Turtle), based on interview surveys there in 2000, and is thought to be scarce (Holloway et al. 2000). This species half-buries itself in muddy substrates in ponds that subsequently dry out during the dry season.  Malayan Snail-eating Turtle Malayemys subtrijuga IUCN Vulnerable. Known colloquially as the “ricefield turtle”, this species is reportedly the most numerous turtle around the Tonle Sap Lake (Holloway et al. 2000, Keng 2003). It is favoured for its meat and is also used in traditional medicine (Balzer et al. 2002). It occurs in floating ricefields in Kompong Thom province between August and December; outside this period it is considered by local people to inhabit inundated forest habitats (Balzer et al. 2002).  Asiatic Softshell Turtle Amyda cartilaginea IUCN Vulnerable Strongly favoured for its meat, it is variously regarded as common, in the Tonle Sap Lake, although has undergone a serious decline (Keng 2003), and quite rare, in Kompong Chhnang (Holloway et al. 2000).

3.5 Community conservation sites

Currently there is only one CPA (Community Protected Area) in Boeung Chhmar Ramsar Site - Balot CPA. The CPA in Balot was formed in 2006-2007 through TSCP. Currently this CPA has been re-functioned by MoE through technical and financial supports by EU-NSA project/IUCN. Its creation emerged from village protests over the privatisation of fishing grounds by local authorities, reflecting a strong community will to protect the area.

In addition to the CPA, there are three CFi (Community Fisheries) sites in the commune, which are apparently more advanced in implementation than the CPA. These CFi sites (in Peam Bang, Dourng Sdeung, and Povouey) are connected to the CCF and receive funds from Forum Syd and FACT. Conservation International also supports two community rangers in each of the three CFi sites to monitor otters and birds.

3.6 Communities and key livelihood activities

There are said to be three kinds of fishing people on the Tonle Sap lake:

 permanent residents living in floating villages:  permanent residents of villages that are on land for six months and on water for six months; and  transient fishers who live on the land and come to fish for three months each year, with the onset of the dry season and after the rice harvests in November.

Fishing livelihoods are finely tuned and highly seasonal. Fishers must make decisions about how to invest their effort in response to myriad risks, trade-offs, and opportunities. They must also account for the dynamic effects of factors such as seasonal changes in water level and quality; weather events; the coming and going of migrants; fish movements around the lake, ponds, canals and tributaries; the role of management and legal instruments, such as the closed season on the lake from October to January; and potential variations in markets that affect fish prices, relationships with middlemen and fuel prices. These factors shape livelihood decision-making in complex and interrelated ways (Marschke and Berkes 2006).

Based on commune statistics of 2013, the communities around Boeung Chhmar consist of 5 villages with 645 households with a total population of 3,351 people of which 1,733 are women (51.7%).

In Boeung Chhmar, about 65% of the population are considered poor, falling into either category 1 or 2 of the government’s poverty rankings. Each village is said to have 10-20 “very poor” families, depending on village size. These families have only wooden row boats, and they must fish everyday in order to eat, selling most of their catch to buy rice. One local leader’s explanation for this ongoing poverty was that fish catches had declined in recent years and that there were many “new” people and outsiders competing for fish in the area. Since the abolition of the lots, however, livelihoods have started to improve.

These narratives indicate people’s high dependence on fish in Boeung Chhmar, and the lack of other livelihood options. On average, poorer families fish for 2-3 hours/day and can catch 5-10 kg of fish or more if they are lucky. Villagers sell all of their catch immediately except what they keep for their own consumption. Some families are also involved in fish processing, such as making prahoc and smoking fish, to sell to “rich” families and traders.

Previously, people would also raise fish, but FiA rangers have prohibited this because they were keeping invasive species. Although they are permitted to raise native fish now, no one bothers because it is not profitable.

There are 4-5 middlemen who come to Peam Bang to buy fish, which they transport to Kampong Lourng in Pursat or Stoung in Kampong Thom depending on the season. The price depends on the market and the middlemen. Fishermen have relatively little bargaining power because: (i) they must sell their fish immediately before it spoils, and (ii) the distance from Boeung Chhmar to other markets is prohibitive for one family to travel alone to sell 10- 20 kg of fish. Families therefore rely on middlemen, who buy fish at 3,000R/kg in Peam Bang and sell it for 10,000R/kg in Kampong Lourng25. This mark-up would more than cover the transportation costs of fish.

The middlemen apparently coordinate with each other so that they all offer the same price to villagers: “you cannot win”, said one villager. People in the commune also have some farmland located in an area that was formerly grassland and is now used for dry season rice production. This 600-hectare area, 5 km from Povouey, was apparently “gift” from the government to compensate for declining fish stocks pre-2012. However, the livelihood ranking for Balot near the CPA, did not mention farming as a livelihood activity. Thus, farming in practice has little bearing on people’s livelihoods near the CPA.

3.7 Perceived non-climate threats and changes

The main non-climate threats to the natural resources of Boeung Chhmar include:

 Dry season rice farming in St. Staung causing water abstraction upstream of Boeung Chhmar, and depleting water levels in the lake during the late dry season  Outsiders coming into fish dry season during March to June  Illegal fishing using fishing techniques such as electric fishing and bag nets  Invasion by mimosa pigra  Invasion by water hyacinth

The removal of the fishing lots has tended to reduce the fishing pressure on fish populations, in particular Fishing Lot No 6, which covered Boeung Chhmar. This has resulted in reduced pressures on the natural resources, since the fishing lot owners used to regard the birds as competitors for the fish. Thus there is no more disturbance and shooting of birds, or burning of trees containing birds’ nests. There is a reduction in the number and extent of fires in the wetland.

4 Management and institutional situation

4.1 Ramsar site

In 1999, Boeung Chhmar (28,000 hectares) was designated as a Wetland of International Importance under the Ramsar Convention. The purpose of this designation is to protect a complex network of wetlands and watercourses recognized as an important fish breeding area, and critical feeding habitat for waterbirds. Boueng Chhmar Ramsar Site hosts 210 species of birds, 107 species of fish, over 30 reptile species, 20 mammal species and 5 amphibian species, although biological research is incomplete (F. Goes 2005 and P. Davidson, 2006). The most recent RIS information was updated in 2012. The Ramsar designation was based upon criteria 1, 2, 5 and 8.

The Tonle Sap Biosphere Reserve (TSBR) was created under the Royal Decree dated 10 April 2001, as the most important inland wetland in Southeast Asia, both for biodiversity conservation and livelihoods based on harvesting of aquatic resources. Three core areas were identified, Prek Toal, Lower Stung Sen and Boeung Tonle Chhmar. The Boeung Tonle Chhmar Core Area is located inside Boeung Chhmar Ramsar Site. The Ministry of Environment (MoE) was designated as the authority responsible for the managing of Biosphere Reserve's Core Areas as well as being the Cambodia focal point for the Ramsar Convention.

Since 2000, MoE has received international support for its program in Boeung Chhmar, initially from the ADB and later from the UNDP Tonle Sap Conservation Project (TSCP) in which IUCN played a role. MoE has a strong presence in the area, for example: Don Sdeung hosts the imposing MoE headquarters for management of the Boeung Chhmar core area. This now run-down structure is built on tall stilts to accommodate seasonal floods and accessible only via a set of broken stairs in the dry season. The station was constructed with funds from an ADB loan. There are 15 MoE rangers and 1 deputy director stationed in the area: 8 at headquarters; 3 in Balot; and 5 at Povouey. The ranger based at Balot was said to be a “local authority” himself. He was very involved in the affairs of Balot and is the main person responsible for the Community Protected Area (CPA).

Both MoE and FiA play roles in protecting the Boeung Chhmar area. Broadly speaking, MoE protects biodiversity and natural resources like flooded forest and wildlife (i.e., the biosphere reserve), while the FiA focuses on fish and prevention of illegal fishing.

The CPA covers 27 hectares, including a 5-hectare Fisheries Conservation Area classified for strict protection, which is located over a deep pool (anlong) next to the sub-village of Ta Our Sar Tuol. The CPA has been demarcated and contains mainly flooded forest.

The CPA or sahakoum in Balot was formed in 2006-2007 through TSCP. Its creation emerged from village protests over the privatisation of fishing grounds by local authorities, reflecting a strong community will to protect the area. According to the local MoE ranger, the CPA was well protected during the TSCP time. Back then, the area was properly demarcated with signboards and patrolled regularly. No outsiders were allowed into the 27 hectares and there were no hyacinth traps. He said the goal of the CPA was to enable the community to “protect mother fish and biodiversity” and that the sahakoum could catch illegal fishers in the area themselves or in collaboration with MoE rangers.

4.2 Management plan

A management plan for the Boeung Chhmar Core Area of the Tonle Sap Biosphere reserve from 2008 – 2012 was prepared by the Tonle Sap Conservation Project for the MoE and MAFF (Tonle Sap Conservation Project, 2007). There is no specific management plan for Boeung Chhmar Ramsar site itself. The Core Area Management Plan was describes the Core Area, and identifies its conservation values and significance. Part Two of the Plan describes management objectives, and identifies priority activities that need to be undertaken to achieve these objectives, including responsible parties and timing. The Plan is intended to be used as the primary resource in the preparation of annual operating plans and budgets, and also provides a basis for evaluating achievement of management objectives. There is no mention of climate change and adaptation, though the analysis of the issues and problems includes:

 The future of commercial fishing in the area  Local livelihoods  Control of fires  Ecotourism development  Management programming, implementation and funding

4.3 Abolition of fishing lot #6 and implications

The permanent abolishment of 37 fishing lots in and around the Tonle Sap lake’s boundary handed over these areas to fishermen’s families for their daily livelihood, and turned the remaining areas (90,000 ha) into Fish Conservation Areas, according to the sub-decree number 37, issued on 07 March 2012. This decision was strongly supported by most fishermen who expect to get much more benefit from fisheries resources. Other people are concerned about the potential increase of illegal fishing, due to limitations of law enforcement of FiA and local authorities, within and around the lake where fish crimes are still rampant.

The conservation of former Lot 6 received many complaints and was said to have a negative impact on people’s livelihoods because there was “too much conservation”. However, this was contested. For example, the MoE ranger said that villagers still went there at night time to get fish illegally and that only sometimes they get caught. He saw the conservation of Lot 6 as vitally important in “preventing disaster”, saying that if the fish in that lot could be protected, then the numbers would increase and fish would spread everywhere, benefitting everyone.

5 Climate – present and future

5.1 Current climate

Like the other parts of Cambodia, the climate of the Boeung Chhmar is dominated by the tropical wet and dry monsoons. The southwest monsoon brings the wet season from mid- May to mid-September / early October, while the northeast monsoon’s flow of drier and cooler air lasts from early November to March. No local weather station exists at the site, but the average annual temperature gauged at Kampong Thom provincial town, about 70km from the centre of the wetlands, shows relatively stable temperatures for the period between 2000 and 2010 (Figure 5.1). The monthly mean maximum temperatures show a peak in March / April of about 35oC, which falls throughout the wet season to about 31oC between September to December

Figure 5.1 Monthly maximum and minimum temperatures at Kampong Thom, 2002- 2010

40.00 2002 Max 35.00 2004 Max 2005 Max 30.00 2006 Max 2007 Max 25.00 2008 Max 2009 Max 20.00 2010 Max 2002 Min 15.00 2004 Min 2005 Min 10.00 2006 Min 2007 Min 5.00 2008 Min 2009 Min 0.00 2010 Min J F M A M J J A S O N D

Source: Department of Water Resources and Meteorology, Kampong Thom

Figure 5.2 Monthly mean maximum temperature at Kampong Thom provincial town, 2002-2010

36.00 34.00 Mean Max 32.00 Temp by 30.00 month, 2002- 28.00 2010 J F M A M J J A S O N D

Source: Department of Water Resources and Meteorology, Kampong Thom

There are 13 stations in Kampong Thom Province recording rainfall data and other meteorological parameters. Average annual rainfall is between 1,300 and 1,900mm. Three stations (Baray, Kampong Thom and Staung) contain fractioned rainfall data record since 1920 until today, showing an annual average value of 1,481 mm, with a peak of 300 mm in September. January, February and December are the driest months. The rainfall data at Kampong Thom town for the period 2000 to 2010 is shown in Figure 5.3 as well as monthly averages (Figure 5.4). Local villages report that rainfall has become erratic, with the wet seasons starting later, until a few years ago when it started earlier. They also note that rainfall is heavier but lasts for a shorter period of time. With heavy rainfall, flash floods on the rivers are also observed. Fewer dry spells have been reported in recent years. （ICEM， 2012）

Figure 5.3 Rainfall measured at Kampong Thom station from 2000-2010

2500

2000 Annual rainfall in 1500 Kampong 1000 Thom (mm)

Rainfall Rainfall (mm) 500 0

Year

Figure 5.4 Monthly average rainfall, measured at Kampong Thom station

Source: Data provided by Department of Water Resources and Meteorology, Kampong Thom

5.2 Future projections

The following section examines the potential climate change trends that are likely to occur in the Boeung Chhmar Wetlands up to 2050.

5.2.1 Climate projection methods

Climate change threats for temperature and rainfall were assessed using six global circulation models (GCMs3) under the International Panel on Climate Change (IPCC) Special Report on Emissions Scenario (SRES) A1B. The modelling approach was selected in order to incorporate the range and variability associated with predicting future climate change. The magnitude and timing of future climate change is dependent on the IPCC scenario selected as each encapsulates a different trajectory for future Greenhouse Gas (GHG) levels in the atmosphere.4 A1B was selected for this study and represents a world of rapid economic growth, introduction of more efficient technologies, global population peaking by 2050 and a balance between fossil intensive and non-fossil energy sources (IPCC, 2000). A1B is considered a conservative GHG emissions scenario, and there is already evidence that GHG emissions during the period 2000 – 2007 exceeded even the most extreme IPCC scenarios for that period (SIDA, 2008).

GCMs include a full description of atmospheric and ocean circulation dynamics which can vary depending on the GCM used. Studies at the global level have identified that GCMs have varying levels of accuracy for different regions (Cai et al., 2008), which means that some GCMs are better at predicting the future climate of the Mekong River Basin than others. The selection of GCMs for use in this study was made based on the GCMs ability to replicate historic precipitation data (Kummu et al., 2011). Seventeen GCMs have been considered in past studies for the Mekong Basin (Cai et al., 2008; Eastham et al., 2009), of these outputs from six GCMs showed good agreement with historic precipitation records for the Mekong and have been selected for use in this study.

All discussion in this report on changes in climate refers to the change in parameters between two 25 year periods: (i) baseline 1980 – 2005, and (ii) future climate, 2045 – 2069. For both time slices models generated daily data for maximum temperature, rainfall, run-off, soil moisture and stream flow. Statistical analysis was then used to extrapolate results for more than a dozen specific hydro-meteorological parameters for example: number of rainy days during the wet and dry season, seasonal rainfall volumes, mean annual rainfall and flow, duration of flood season, occurrence of consecutive hot days, peak and minimum flows and these were applied as relevant to specific wetland types and case study sites.

Although the models show some differences in results they are in agreement regarding the general trends in temperature and rainfall. The methods for climate projections are more fully described in the MRC wetlands and climate change study and in the Mekong ARCC study. （ICEM，2012）（ICEM，2013）.

5.2.2 Temperature changes

Increasing temperatures are projected for daily maximum and minimum temperatures at the wetlands, the number of hot days is also expected to rise. The average temperature in

3 GCMs utilised in this study include: CCMA_CGCM3.1 (Canada); CNRM_CM3 (France); NCAR CCSM3 (NCAR USA); MICRO3_2hires (Japan); GIIS_AOM (GODDARD USA); MPI_ECHAM5 (Germany); MPI_ECHAM4 (Germany). 4The IPCC published a new set of scenarios in 2000 for use in its Third Assessment Report, known as Special Report on Emissions Scenarios (SRES). The SRES scenarios were constructed to explore future developments in the global environment with special reference to greenhouse gas emissions. Four narrative storylines were defined, A1, A2, B1 and B2. Each storyline represents different demographic, social, economic, technological, and environmental developments (IPCC DDC, 2011a).

Cambodia from 1960 to 2005 has increased by 0.8°C (McSweeney et al., 2008). Although quite substantial differences are predicted between the different models, there is a general agreement among all the models that there will be an increase in temperature in both wet and dry seasons at Boeung Chhmar. Figure 5.5 shows the monthly average temperatures with ranges of high and low records or projections. This shows a much wider range for the projected increases than for the baseline, but this may be an artefact of the use of different GCMs. At the hottest time of year (March/April/May) the average temperature is likely to be increased from about 28oC to over 30 oC. In the wet season, the monthly average temperatures are likely to be increased from 26oC to 28oC.

Figure 5.6 shows monthly average maximum temperatures, and here we can see that the baseline maximum temperature in March of 32 oC is likely to be increased to 35 oC with the period of high temperatures extending through into early May. In the wet season, August, the monthly average maximum temperature is likely to be increased nearly 4oC from 27.5 oC to over 31oC.

Figure 5.7 shows the daily maximum temperatures with the mean (middle darker line) showing peaks of 35 to 36 oC projected for March / April compared to the baseline figures of 31-33 oC. The hottest peaks expected during this time are likely to be increased from 37 to 39 oC to 40 to 43 oC.

Figure 5.8 shows a similar but more moderated pattern for the minimum temperatures throughout the year with the baseline ranging from 19oC in December/January through to about 24oC in May to October. With climate change projections, the minimum temperatures may increase from 21 oC in January to 25 oC through the late dry season and wet season.

Figure 5.5 Monthly average temperatures for baseline (1980-2004) and climate models

(2045-2069)

Source: ICEM

Figure 5.6 Maximum temperatures for baseline (1980-2004) and climate change models

(2045-2069)

Source: ICEM

Figure 5.7 Daily maximum temperatures for baseline (1980-2004) and climate change models (2045-2069)

Source: ICEM

Figure 5.8 Daily minimum temperatures for baseline (1980-2004) and climate change models (2045-2069)

Source: ICEM

The projections thus indicate that there could be a 2 – 4 deg C rise at different times of year. This will result in an increase in the number of very hot days. This is shown in Figure 5.9. If the threshold for a very hot day is taken as 35oC, under baseline conditions a proportion of about 0.03 days in the year exceed that daily average or 11 days per year. Under climate change projections this will increase to a proportion of about 0.14 or 51 days per year.

A similar assessment of cold days with a threshold of less than 20oC, shows that under baseline conditions the 40 days recorded minimum average temperatures below 20 oC, while this would be decreased to about 15 days per year by 2050.

Figure 5.9 Annual proportion of daily exceedance of maximum (left) and minimum (right) temperatures

Source: ICEM

When the temperature ranges are considered for “comfort zone” analysis, Figure 5.10 shows that in the wet season the projected temperature shift lies completely outside the earlier comfort zone for the baseline during the wet season, whilst the dry season shift is about 60% outside the dry season comfort zone. The right hand chart in Figure 5.10 shows that the wet season shift lies within the overall comfort zone for the year and only the dry season shift lies outside the year’s comfort zone. These differences will be important if there are seasonally critical stages in the lifecycle of the species.

Figure 5.10 Maximum temperature comfort zone analysis of temperature range shifts, differentiated by wet and dry season (left) and over the whole year (right). Source: ICEM

Similar comfort zone analysis for minimum temperatures are shown in Figure 5.11, with very similar pattern showing the wet season minimum temperatures lying completely outside the comfort zone, and about 50% of the dry season minimum temperatures lying outside. This is the same for the overall annual comfort zone.

Figure 5.11 Minimum temperature comfort zone analysis of temperature range shifts, differentiated by wet and dry season (left) and over the whole year (right)

Source: ICEM

When maximum and minimum temperatures comfort zones for Boeung Chhmar are combined in one diagram in Figure 5.12, it can be seen that the changes in minimum

55 temperatures will always lie within the ecological comfort zone, but that the maximum temperature ranges for both wet season and dry season are significantly outside the ecological comfort zone.

Figure 5.12 Combined maximum and minimum comfort zones for Boeung Chhmar

Source: ICEM

5.2.3 Rainfall

For Boeung Chhmar, precipitation is expected to fluctuate for the projected period (2045- 2069) under climate change, with a slight increase in the total amount of rainfall in both dry and wet seasons, and in the number of rainy days. The total average annual rainfall for the baseline is 1,249.3 mm/yr split between wet season of 975.1 mm from June to November and dry season of 274.2 mm from December to May. With climate change to 2050, this is expected to increase to 1381.4 mm per year split between wet season at 1,091.0 mm and dry season 290.4 mm. This represents an annual increase of 10.6%, a wet season increase of 11.9% and a dry season increase of 5.9% (Figure 5.13). The distribution of these changes is variable, with slight decreases in January and February, and a bigger decrease in April (- 7.5%). May shows increases of +13.2%, while the biggest increase in monthly rainfall is expected in September (+17.8%).

Figure 5.14 shows that the number of rainy days with a given amount of rainfall will be increasing in both dry and wet seasons. The “+”s of the different GCMs generally appear to the right of the baseline numbers of rainy days for a given rainfall.

Figure 5.13 Average monthly rainfall at Boeung Chhmar, baseline and future climate change (2045-2069)

Source: ICEM

Figure 5.14 Total rainfall vs total number of days of precipitation, dry season (left) wet season right for baseline and GCM average

Source: ICEM

Figure 5.15 shows an analysis for the start of the monsoon. The indicator for the start of the monsoon is taken as the first month in the year when the rainfall exceeds 200 mm. In a very dry years, it may happen that the rainfall never exceeds 200 mm in a month – for the baseline this occurred in 8% of the years, while under climate projections this will be reduced to 4% of years – in other words very dry years will become less frequent. In the figure it appears that the percentage of years when the monsoon starts in May and June will increase from 16 to 28% for May, and from 28 to 40% for June. For the later months, July shows the same percentage for baseline and CC projection, while August and September show reductions in the number of years when the rainfall first exceeds 200 mm. This points to a generally earlier start to the monsoon under climate change.

Figure 5.15 Start of the monsoon as indicated by first month of the year in which the rainfall exceeds 200 mm

Source: ICEM

The analysis of ecological comfort zones for rainfall is shown in Figure 5.16. This shows that the rainfall in the dry season under climate change remains more or less within the comfort zone of the baseline. The wet season rainfall under CC projection lies about 60% above the comfort zone of the baseline.

Figure 5.16 Ecological comfort zones for rainfall for Boeung Chhmar, by wet and dry season (left) and combined for the whole year (right)

Source: ICEM

Figure 5.17 shows the spatial differences in rainfall distribution under climate change. The left hand map indicates that the baseline rainfall is quite evenly distributed around Kampong Thom at between 1,201 to 1,400 mm per year. However, the percentage change around Boeung Chhmar and the Tonle Sap lakeshore is lower than areas further to the east e.g. around Stung Treng.

Figure 5.17 Annual average precipitation and % precipitation change in 2050 in Kampong Thom province, Cambodia

Note: The green dot indicates the location of the point time series data. Source: ICEM

5.2.4 Storms and extreme events

It is generally considered that storms and extreme events are likely to increase in frequency and intensity with climate change. Figure 5.18 shows a ranking of the maximum daily precipitation in the year. This is taken as an indicator for storm events, when the rainfall in one day ranges between 50 mm to 150 mm per day.

An analysis of this diagram shows that there are 7 days per year in the baseline when there is 80 mm or more rainfall. Under climate change, the projections indicate that the frequency may increase to 11 times per year. The intensity of the rainfall that falls during all storm events is likely to increase. Thus the highest rank storm event would see an increase from about 170 mm to about 190 mm in a day, an increase in intensity of about 12%. Lower ranked storms consistently show increasing rainfall falling in a day.

Figure 5.18 Ranking of annual maximum rainfall events

Source: ICEM

5.3 Local perceptions of climate trends and extreme events

At the Lower Stung Sen Wetlands, local people have reported that there is warmer weather overall and an increasing number of hot days and nights. Notably, they mention that the hot season seems to start earlier and finish later, and that the rainfall does not have as much cooling effect as in the past. The warm weather tends to last longer and littoral waters become too hot to step in and even caged fish die. (ICEM, 2012)

Local people gave no reports of drought, although they noted an unusual lack of monthly rainfall in the dry season in recent years. Low water levels in the Tonle Sap Lake (e.g. due to a prolonged drought in 2010) are becoming more common, as well as the quicker recession of the water level early in the dry season. There are also mixed observations by local villagers regarding other extreme events. While some noted increasing storms and strong winds, other residents disagreed. Flash floods on the Stung Sen River are also a concern, and can break houses away from their anchors. (ICEM, 2012)

An important implication of climate change for local livelihoods in the Boeung Chhmar wetlands is the expected increase in frequency and intensity of natural disasters, particularly storms. As an example Kampong Thom Province was the worst affected area by Typhoon Ketsana in 2009 and floods in 2011, especially along the Stung Sen River. The combination of the typhoon and torrential rain in 2009 affected 447 out of 738 villages from all districts in the province, destroying 109 houses and 428 roofs, and partially destroying another five houses. Altogether 33,687 families were affected with 16,990 families becoming vulnerable, 20 people reported as dead and 45 injured. Interviews with provincial and local authorities and local communities revealed that Ketsana damaged 45,989 ha of paddies in the province, with 13,451 ha recovered while 20,753ha were completely destroyed (at a total cost USD 8,820,025). Losses of other productive assets were reported to be USD 190,525. Losses and damage from the typhoon also put more pressure on food security and irrigation development along the Stung Sen River. In 2010, a prolonged drought also affected many fish in the Tonle Sap Lake. Most of the fishing communities involved in this study reported

60 lower fish catches during this period, and some ponds dried out. In addition, there were floating houses lost to storms and loss of other assets such as pigs and chickens. In 2011, the province suffered flooding again, in particular damaging rice crops, human health and the education sector.

It is noted that Boeung Chhmar has a much smaller catchment area than the Stung Sen, with the combined catchments of Stung Staung and Stung Chikreng being less than half the area of Stung Sen, and so the risk of flash floods is likely to be lower.

5.4 Hydrology and habitat changes

The hydrology of a wetland is the most fundamental characteristic that defines it and the habitats. Climate change is likely to change the rainfall patterns as described in chapter 5, so that overall there will probably be at least 10% more rainfall during the year, in both wet and dry seasons. It would appear however, that most of the increase in rainfall in the dry season will occur in May, which could be seen as a tendency to bring the start of the monsoon earlier. It is probable therefore that the main part of the dry season will be drier – excluding the rainfall projections for May, the dry seasons in 2050 are likely to have about 4% less rainfall.

At the same time the temperature during the late dry season is likely to increase by 2 – 3 deg C, which will have implications for the rate of evapotranspiration from open bodies of water and wetlands. There thus may be increased drying out and water stress on the wetlands during the later dry season (March/April). So it is to be expected that the Boeung Tonle Chhmar and the surrounding creeks will be even shallower during the late dry season in 2050 than at present.

The start of the wet season (the first month in the year with more than 200 mm rainfall) is more likely to occur in May and June (68% of years compared to the baseline of 44% of years), so the first flush of water down the Stung Staung and Stung Chikreng is likely to be more predictable, and the typical total rainfall during those two months will be 377.8 mm compared to the present 338.2 mm – an increase of 11.7%. Given that there is likely to have been less water available for the wetland in the late dry season, this extra rainfall during the early wet season may compensate for the water shortage.

Thereafter, the hydrology of the Boeung Chhmar will be more influenced by the water levels in the Tonle Sap Great Lake and the backwater flow from the Mekong than the additional rainfall in the locality of the Ramsar site and its catchment from the Stung Staung and Stung Chikreng.

A recent paper by Arias et al. (2012) has attempted to quantify the changes in flooding and habitats in the Tonle Sap due to water infrastructure and climate change. They identified five clear habitat groups around the Tonle Sap – open water, flooded for 12 months in an average hydrological year; gallery forest flooded for 9 month of the year; seasonally flooded habitats, flooded for 5 – 8 months of the year and dominated by shrublands and grasslands; transitional habitats, flooded for 1 – 5 months and dominated by abandoned agricultural land, receding rice/floating rice and lowland grasslands; and, rainfed habitats, flooded up to 1 month and consisting mainly of wet season rice fields and village crops.

They considered the hydrological impacts upon the flooding levels in the Tonle Sap from several scenarios involving the development of hydropower in the Mekong Basin and, separately the impacts of climate change to 2030. Whilst the climate change models used will be slightly different from the projections used in this study, it is useful to use this analysis to understand the projections for flooding due to the Mekong, rather than the local rivers.

Figure 5.19 shows the comparison of water levels at Kampong Loung (opposite to Boeung Chhmar) for average, dry and wet years in 2030s for climate change and infrastructure development. During wet years there is very little change observed in the shape of the water level curve throughout the year for climate change impacts and only a slight decrease due to water storage in infrastructure. During average years, mean water levels during October/November (the peak flood) may be increased by 0.5 m due to climate change (to 9.5 masl). The impacts of water storage infrastructure would decrease the peak by about 0.35 m.

During dry years, the changes are more pronounced. With climate change, water levels remain the same during the low water months of April and May, but increase by 0.2 to 0.75 m during the rest of the year. With infrastructure development, water levels increase by 0.2 – 0.4 m from April to June and decrease by up to 0.5 m from August through to January.

Arias et al (2012) estimated the extent and duration of the annual flooding in the Tonle Sap floodplain. The overall flood extent for an average year is expected to increase by about 1,000 km2 due to climate change impacts and to decrease by 196 – 710 km2 due to infrastructure development. This is shown in Figure 5.20. A similar trend is observed for a dry year with a minor increase as a result of climate change (75 – 225 km2 and an overall decrease in flood extent by 513 – 681 km2 for infrastructure development. For wet years the total flood remains relatively constant for the different scenarios, but there are substantial differences in flood duration zones.

Figure 5.19 Comparison of mean monthly water levels at Kampong Loung for historical observed records and model predictions for a) an average year, b) a dry year and c) a wet year.

Note: 2030CC = climate change scenario for 2030’s; 2030DEV = water resources infrastructure development scenario for the 2030’s.

Source: （Arias，2012）

Figure 5.20 Annual flood duration (months) and extent during a) an average year

b) dry year and c) wet year

Source: Arias 2012

Legend in Units of months. UMD = Upper Mekong dams; 2030DEV = water resources infrastructure development scenario for 2030’s; 2060DEV = water resources infrastructure development scenario for 2060’s; 2030CC = climate change scenario for 2030’s; 2040CC = climate change scenario for 2040’s.

Figure 5.21 Flood duration (months) zone dominance - % of flood zone area covered by each of five habitat types during a) average years, b) dry years, c) wet years.

Source: Arias 2012

When these flood duration extents are translated into the five predominant habitats as shown in Figure 5.21, a series of flood duration rules were developed for modelling habitat cover (Table 5-1) these were then used to project changes in habitat resulting from the

65 different scenarios. The changes in area of modelled habitats compared to the original are shown in Table 5-2.

Table 5-1 Flood duration rules used for modelling habitat cover in the Tonle Sap

Clustered Land use/Land Cover Months of annual flood duration Cover area habitat classes Average year Dry Wet year km2 year

Rainfed Wet season rice, village 0 -1 0 0-3 8,641 habitats crops, lowland shrubland

Transitional Abandoned fields, floating 1-5 0-1 3-6 3,658 habitats and receding rice, lowland grassland

Seasonally Flooded shrubland, flooded 5-8 2-7 6-11 5,409 flooded grassland habitats

Gallery Gallery forest 9 9 9-12 197 forest

Open water Open water 10 -12 9-12 10-12 3,027

TOTAL 21,067

Source: Arias 2012

Table 5-2 Area changes in modelled habitat cover from the baseline as a response to future scenarios

Scenario Rainfed Transitional Seasonally Gallery Open habitats habitats flooded forest water habitats

Km2 % Km2 % Km2 % Km2 % Km2 %

2030CC -201 -2 -265 -6 339 7 84 13 42 2

2040CC -384 -5 84 2 219 5 -451 -69 531 21

UMD 813 10 -189 -4 -612 -13 -537 -82 525 21

2030DEV 1061 13 -281 -6 -810 -17 -536 -82 567 22

2060DEV 1215 14 -133 -3 -1041 -22 -495 -75 454 18

Source: Arias 2012

UMD = Upper Mekong dams; 2030DEV = water resources infrastructure development scenario for 2030’s; 2060DEV = water resources infrastructure development scenario for 2060’s; 2030CC = climate change scenario for 2030’s; 2040CC = climate change scenario for 2040’s.

In summary, the area of rainfed habitats tends to decrease slightly with climate change but increase between 10 – 14% with infrastructure development in the basin. Transitional habitats mostly decrease slightly with all scenarios, except for the 2040 climate change scenario. Seasonally flooded habitats, increase between 5 and 7% for climate change scenarios 2030 and 2040 respectively, but decrease between 13 – 22% with infrastructure development. Gallery forests are the habitats that are squeezed the most by both longer- term climate change and infrastructure development. Climate change by 2030 indicates a slight increase in gallery forest extent, but this is reversed by 2040, with a 69% loss and conversion to open water, which shows a 21% increase for 2040 climate change and similar changes for the infrastructure development scenarios.

When the impacts of climate change and development of infrastructure are combined it is possible to observe two important features of the impacts upon water levels in the Tonle Sap, which will have an impact upon the habitats in Boeung Chhmar. These are illustrated in Figure 5.22 which shows how the development of infrastructure is likely to increase the water levels in the dry season by up to 80 cm5. In the wet season, the increased water levels induced by climate change are moderated by the storage of water by hydropower plants, thus the overall flooding levels in the wet season will be slightly less than the baseline. (Sokrith, 2013). These are shown in Figure 5.23. When these changes are translated into the extent of flooding in the Boeung Chhmar area (Figure 5.24) it can be seen that there is a marked increase in open water and losses of flooded forest, except for a few fringing areas along the shorelines and levees.

Figure 5.22 Monthly water levels at Kampong Loung during an average year, with impacts of hydropower development in the Mekong basin and climate change

Climate change and hydropower impacts on an average year 11 10 rvmpa rvcca 9 rvgia 8 rvnca 7 A1b models + hydropower observed average 6

masl Hydropower 5 4 3 2 1 May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

Source: Arias 2012

5 Hydropower development tends to store water in the wet season and release it in the dry season

Figure 5.23 Spatial extent of flooding in a) dry season – increase of about 30% compared to baseline (left) and b) wet season – decrease of -10% compared to baseline (right)

0 25 50 100 Kms

Source: Arias 2012

Figure 5.24 Habitat changes from the baseline around Boeung Chhmar due to upstream hydropower development in 2030s and Climate change in 2040’s

Source: Presentation by Heng Sokrith, Conservation International 2012, based upon （Arias，2012）

6 Vulnerability assessment

6.1 Summary of main climate threats

From the temperature projections,

 Highest temperatures occur between late Feb and beginning of May, currently ranging between 31 and 33oC. This is likely to increase to between 33 to 36 oC, with a slightly lower temperatures earlier on in February and the higher temperatures extending into May.  Maximum daily temperatures may reach 40 oC during this time, but this would increase to 42/43 oC  After May the temperatures fall steadily to lower points in June through to November when the range between 27 and 29 oC. During this period the mean maximum temperature will range between 30 and 32 oC  Temperatures are lowest in November/December with mean maximum temperatures around 27 oC this is likely to rise to 29 – 30 oC. and starting to rise in late December steadily through January and February.  The biggest differences occur in the wet season.  In terms of numbers of very hot days above 35 oC, currently at 11 days per year, would increase to 51 days per year.  Temperature increase in wet season lies entirely outside the normal comfort zone, and partially outside in the dry season, though only dry season lies outside the comfort zone.  Minimum temperatures currently lie in the range 23 - 24 oC for most of late dry and whole wet season – this will rise to about 25 oC. Minimum temperatures fall to the lowest in December at 18.5 - 19 oC and this is likely to increase to between 20- 21 oC. Minimum daily temperatures may fall as low as 11 or 12 oC and these minima are also likely to increase by about 1 – 2 deg C.  Number of days with temperatures below 20 oC increase from about 15 days per year to about 40 days per year.  Both dry season and wet season minimum temperature comfort zones are exceeded

From rainfall projections:

 Average annual rainfall per year is currently 1,249.3 mm (274.2 mm dry season, 975.1 mm wet season). This is likely to increase to 1,381.4 mm (290.4 mm dry season, 1,091 mm wet season) this is an overall increase of +10.6% (+5.9% in dry season, +11.9% in wet season).  Rainfall in January and February slightly reduced, and also in April. Increased in May and each of the wet season months, slightly increased in December.  Biggest % change is in February with a 16% decrease. % increases are highest in September and October – above 10%.  Months when first monsoon rainfall is more than 200mm increase in May and June, so there is more likely to be an earlier start to the monsoon rains.  Rainfall in wet season is likely to be more increased outside of the comfort zone, but in the dry season it lies within comfort zone.

 Number of storm events when the daily precipitation is more than 80 mm in a day, increases from 7 events per year to 11 events per year.  Storm intensity increases – largest storm per year has about 170 mm, in the future will have 190 mm, an increase of about 12%.

6.2 Vulnerability of key physical and ecological processes

Using the seasonal calendar shown in Table 3-1, the pressures and changes that may be expected in these key physical and ecological processes can be described. These changes are summarized in Table 6-1. The description of the vulnerability of the different ecosystem processes is highlighted in bold in the table.

Table 6-1 Main climate changes expected at different seasons and possible impacts on key physical and ecological processes in Tonle Sap

Mean maximum temperatures follow Reversal of Tonle Sap River Out-migration of terrestrial general pattern In May, water levels flow into Tonle Sap Lake - In-migration of "white fish" Tree and shrub flowering and fruit production breeding species (grassland decreasing from peak in B.Chhmar likely to floodpulse begins from Mekong via Tonle Sap Higher temperatures may speed up process of flowering birds and larger mammals) as at beginning of May be lower than Under CC this is unlikely to be River and fruit production. Very dry conditions in early May could flood rises to low in July. currently due to felt immediately in B. Will not really affect B. affect flowering, causing flowers to shrivel and dry up Possible earlier departure as Increase in mean hotter dry season Chhmar until later in the Chhmar before fertilisation flood water rise earlier in the daily maximum is of year season the order 3 - 4 deg C

In-migration of post-breeding Deepwater rice crops large waterbird congregations Monsoon rainfall germinating in outer In-migration of "white fish" for feeding, nesting and (storks, ibises, herons and Current pattern is more likely to start in floodplain spawning In migration of white fish would egrets, pelicans) 31/32 C in May to 27 May in c. 30% of Increased temperatures may wait until waters start to rise in swamp forests, likely to Possible earlier arrivals of C in July, Early years affect germination of deep beearlier rather than later in season large water birds to May-July monsoon water rice B.Chhmar to take advantage of earlier floods In-migration of wet-season With climate change Watersnake harvest begins breeding waterbirds (e.g. this mean daily Nearly 11% more Lateral migrations of "black fish" to nesting and spawning Early rains and rising water rails, crakes, bitterns) maiximum is rainfall expected in habitats levels in B.Chhmar may alter Possible earlier in-migration increased from 35 C May to July in typical Spawning habitats likely to be inundated in back swamps the emergence of water to take advange of earlier in May declining to 31 years earlier in the season snakes from burrows inundation of grasslands C in July and increase in food supply Water levels in B. Departure of large waterbird Partially outside In-migrations of some black Chhmar likely to breeding colonies (storks, comfort zone in May and white fish species for increase faster in pelicans, ibises, herons and and as wet season nesting, spawning and early wet season due egrets) progresses, juvenile growth. to rainfalling in Possible earlier arrivals of temperature Spawning habitats likely to catchment of S. large water birds to generally outside be inundated in back Staung and S. B.Chhmar to take advantage comfort zone swamps earlier in the season Chikreng of earlier floods

Season Month(s) Climate change influence Key Physical, Land- and Ecological Processes/Events by Habitat Type Human-use Processes Temperature Rainfall/hydrology Open Lake Swamp forests Short-tree shrublands Grasslands/agro-ecosystems Expansion of Tonle Sap Lake Mean monthly to max. inundation through Rainfall in three temperature is fairly reverse flow mechanism and Tree and shrub flowering and fruit production - Higher months increases constant, baseline 26 - catchment rainfall - wet temperatures may speed up process of flowering and fruit from 598 mm to 27 C likely to increase season flood extent production. May lead to lowered fertility of seeds 655.2 mm (+9.5%) to 28 - 29 C (+2deg C) expected to be higher and longer Mean max Largest sediment inputs - Increased input from temperatures sediments come mainly from St. Staung and St. Deciduous tree leaf fall (underwater) - unaffected increase from 28-29 C Mekong, will not affect B. Chikreng to 31-32C (+3 deg C) Chhmar Fish nesting, spawning, feeding and juvenile growth Fishing (outside lot system) in period - higher flood levels Fish nesting, spawning, feeding and juvenile growth period - outer floodplain agro- will tend to make more Wet season comfort Increased back flows higher flood levels will tend to make more breeding sites ecosystems - floodplain breeding sites and food zone exceeded by 3 from Mekong flows and food availability. Increased air temperatures unlikely likely to be inundated for availability. Increased air August- deg C into Tonle Sap to be reflected in water temperatures because of higher Midmonsoon longer and higher and temperatures unlikely to be October water levels fishing may be improved reflected in water temperatures because of higher water levels Cormorants and Darters Main phase of deepwater rice Deepwater rice crop main return to nest colonies and growth in the outer floodplain Water levels in B. growth phase - Increased commence breeding - higher agro-ecosystems - Increased Chhmar expected to temperature and availability air temperatures may affect temperature and availability be higher of water likely to enhance the breeding of these birds of water likely to enhance growth in B. Chhmar, earlier growth hatching Watersnake breeding period - Watersnake breeding period - Increased water Increased water Watersnake harvest peaks - Fish perform function of Possibility of temperatures moderated by temperatures moderated by higher water levels may tend natural pest regulators in increased intensity high water levels, so increase high water levels, so increase to disperse water snakes traditional rice agricultural storms in temperature may have in temperature may have more systems - unaffected less effects on water snakes less effects on water snakes breeding breeding

Season Month(s) Climate change influence Key Physical, Land- and Ecological Processes/Events by Habitat Type Human-use Processes Temperature Rainfall/hydrology Open Lake Swamp forests Short-tree shrublands Grasslands/agro-ecosystems Mean monthly temp Flood water begins to recede Rainfall shows an falling from 26.5 in as Mekong River level drops overall increase of + Out-migration of "white fish" early Oct to 25 C in and Tonle Sap River reverses 25 mm or 11.2% in to Mekong River via Tonle Sap Leaf flush in all deciduous and evergreen tree species - Continued growth of "floating late Nov. This will flow again and begins these two months River and floodplains - Unaffected grasses" - Unaffected change from 28 C in draining the lake - increased with most of increase unaffected early Oct to 27 C in rainfall in October could in October late Nov (+1.5 - 2 Deg delay recession in B. Chhmar Mean max temperatures fall October- from 28 to 27 C Oct to Large-scale commercial Late monsoon Possibility of November Nov. with CC this fishing begins in all fishing lots Watersnake breeding period - increases in temperature increased intensity likely to increase to and main waterways draining could affect water snake breeding and hatching of eggs storms 32 to 30 C Oct to Nov. Tonle Sap lake - Unaffected Daily peaks could increase from 34 C to Mean minimum Deepwater rice ripening temps fall from 23 C phase - increased rainfall in Oct to 20 C in late and delayed recession could Nov. With CC this will delay ripening change to 25 C to 22 C Mean monthly In-migration of terrestrial Large-scale commercial temperature falls Rainfall shows slight Out-migration of "white fish" breeding species begins fishing continues in all fishing Cormorants and Darters from 25 to 24 C and increase in three to Mekong River via Tonle Sap (grassland birds including lots and main waterways complete breeding and fledge rises again in Jan. This months - only 4% River and floodplains Bengal Florican) as land draining Tonle Sap lake - - unaffected is likely to increase increase continues - unaffected reexposed on flood recession - Unaffected from 27.5 falling to 26 Unaffected Mean max temps go All of the increase from 28 - 30 C to 30 - comes in November Large in-migration of Flood waters recede Large waterbirds (storks, 32 C (+2 deg C) (51.7 to 54.3 mm) Dec Palearctic "winter visitor" bird increasingly rapidly - flood Large feeding aggregations of ibises, pelicans, herons and Daily peak shows slight decrease populations (raptors, chats, November- recession rate likely to terns and gulls - unaffected egrets) return to nesting Early dry temperatures, very (6.5 to 6.4 mm) and hirundines, warblers, pipits, January increase colonies - unaffected hot days range from January 0.6 to 0.5 wagtails) - Unaffected 32 - 35 C increasing to mm Mean min temps November baseline range around 19 -21 showed 6% of years Second watersnake harvest C baseline increasing when they received peak - unaffected to 20 - 23 C more than 200 mm of Comfort zone for Deepwater rice harvest - temperature not early harvest of deep water exceeded during rice possible as recession these three months rate increases

Season Month(s) Climate change influence Key Physical, Land- and Ecological Processes/Events by Habitat Type Human-use Processes Temperature Rainfall/hydrology Open Lake Swamp forests Short-tree shrublands Grasslands/agro-ecosystems Main breeding period for Large-scale commercial large waterbrids (storks, Mean temp rises Concentration of black fish as Rainfall in Feb to April fishing begins in all fishing lots ibises, pelicans, herons and Main breeding period for from 26 - 28C during surrounding floodplain dries will decrease by - 4.6 and main waterways draining egrets) - Less relevant for B. terrestrial grassland birds period. This will out - black fish likely to mm of -4.2% from Tonle Sap lake - Rapidly Chhmar (more for Prek Toal), (e.g.Bengal Florican, quails increase by 2 deg C to congregate in B. Tonle 110.3 to 105.7 mm falling water levels in B. but increases in temperature and buttonquails) 28 - 30 C. Chhmar Chhmar may affect fishing could affect breeding and fertility of eggs

Black fish concentrated in Large feeding aggregations of High concentrations of fish remaining waterbodies and terns and gulls - Shallow behind fish traps in fishing Mean max temp rises Rainfall in Feb to May Increasingly drought like Black fish concentrated in performing "overland" water in B. Tonle Chhmar lots - no longer relevant from 30 to 32 C and will increase by +16.2 conditions develop in outer remaining waterbodies and migrations - High water likely to make fishing for since fishing lots abolished, will increase by 3 deg mm of +6% from floodplain - This is likely to performing "overland" temperatures in exposed gulls etc easier and so may but lower water levels will C to 33 - 35 C. 267.1 to 283.3 mm be intensified migrations small bodies of water, may see greater concentrations mean higher concentrations be over comfort zone even of of gulls and terns of fish black fish Decreased rainfall Estimated main breeding Estimated main breeding from Jan to April period for turtles and pythons period for turtles and pythons Local movements of Palearctic Extensive burning of Peak daily temps in coupled with - Higher temperatures may - Higher temperatures may birds in response to grassland and shrubland - March April range increased mean reduced fertility of mean reduced fertility of availability of key food With increased drought Mid-late dry January-May about 37 - 39 C will temperatures will eggs, especially if nesting eggs, especially if nesting resources - patterns of conditions, risk of fire increase to 40 to 43 C increase rate of fall of sites are exposed. May also sites are exposed. May also movement may be affected outbreak will increase water levels in change sex ratio in change sex ratio in if drought conditions persist B.Chhmar populations of turtles populations of turtles Domestic livestock may partly fulfil grazing function of extirpated herbivore Max temp comfort populations - generally Livestock grazing (January- zone will increase Also note windstorms unaffected but potentially early April) - Potentially from 28 - 33 C to 31 in April May when shortage of fodder if shortage of fodder if to 35 C, so with CC water levels in B. drought conditions persist drought conditions persist will be partially Chhmar are lowest and intensify. Livestock may and intensify outside comfort zone need to go further into wetland for grazing and browsing, which may damage vegetation. Preparation of land for Minimum temps deepwater rice cultivation - range 22 - 24 C which may be affected if drought will increase to 23 - conditions persist, but may 25 C be alleviated by increased rainfall in May 74

6.3 Key habitats

The vulnerability assessment sheets for the key habitats are presented in Annex 1. The summaries are presented below; these focus on the main exposures, sensitivities and adaptive capacities of these habitats and their overall vulnerability to specific climate changes and extreme events.

6.3.1 Open water

The focus for this assessment of open water is the lake, Boeung Tonle Chhmar. There are other smaller bodies of open water and these may experience similar impacts. The following climate change threats are identified with their impacts and overall vulnerabilities:

 High temperatures  Substantially increased water temperatures during the dry season  Increased evapotranspiration from water surface during dry season  Dissolved oxygen of the water will decrease with increased temperature  During wet season the temperatures are lower overall, there is more water and deeper water and the impacts of increased temperature will be less.  Increased rainfall in wet season  Water levels in B Chhmar will rise faster in early wet season, but not perhaps as fast as Lower Stung Sen because catchment is half the size  Sediments in B Chhmar mainly from two rivers rather than from Tonle Sap  Rainfall over the Tonle Sap catchment will be more important for 2nd rise in water level  Backwater from Mekong into Tonle Sap and into B Chhmar gives the 3rd rise and biggest rise in water level  More irregular rainfall in dry season  Reduced water levels in open water in dry season  Increased abstraction of water for dry season rice upstream which will add to falling water levels, including backflow from B Chhmar up into St Staung ground water  Water remains stagnant in B Chhmar  Water levels very shallow (less than half metre at moment)  Longer period of dry season  Water level remains low for longer maybe for 1 – 2 weeks before starts rising in early wet season  In combination with increased temperatures, dissolved oxygen of remaining water will be lowered  Increased balance between precipitation and evapotranspiration in April  Less water available in the open water, water levels falling in late dry season, especially in April  More strong winds in April and May  Water temperature is very high, sediments and poor quality water are churned up and mixed with water  Massive fish kills especially of white and grey fish  Blackfish seem less sensitive

 Increased frequency and intensity of storm events  Storms will tend to churn up the water in the lake increasing turbidity and mixing of water at different levels  Risks for fishermen in open boats

Table 6-2: Vulnerability matrix for Open water habitats

Impact Adaptive Threat Exposure Sensitivity Level capacity Vulnerability

High Temperature VH VH VH L VH

Increased rainfall in wet season VH VH VH H H

More irregular rainfall in dry season VH VH VH VL VH

Longer period of dry season H H H M H

Increased P/PET balance in April VH VH VH L VH

Change and shift in events

Strong winds VH VH VH VH VH

Storm events VH M VH VH H

The open water of Boeung Chhmar shows generally very high vulnerability to climate change which is likely to affect both the extent of the open water during the flood season and the depth and water quality of the open water in the dry season. Because it is so shallow, especially in the dry season, the water will become much hotter with the increased temperatures under climate change. It is particularly vulnerable to the strong winds that occur late in the dry season when the water is overturned and poor quality water is mixed up from the bottom layers, causing massive fish mortality.

6.3.2 Gallery forest – alongside Tonle Sap and along river banks

 High Temperature  Increased evapotranspiration from leaves due to high temperatures in late dry season, this is when the leaf cover is highest. Trees lose leaves in July as they get flooded.  New leaves come in January, Flowers in April, fruiting in early rainy season  Seeds dispersal in July.  High temperature may reduce growth and reduce the fertility of seeds, because a lot of energy used for evapotranspiration  Terminalia (Ta Ue) is seen as most vulnerable species because of lower density than other species and high demand for firewood  Increased rainfall in wet season  Early rainfall and run-off from St Staung and Chikreng important for rise in water levels in May June

 More important are water levels from Mekong backflow which will determine the extent depth of the flood  Increased wet season water levels  There will be a tendency to lose gallery forest at the Tonle Sap shore line and gain it at the expense of flooded shrubland  More irregular rainfall in dry season  Risk of forest fire likely to increase under drier conditions  Riang and Phthuol more resistant to fire than Ta ue  Increased P/PET balance in April  May have impact upon flowering and fruiting success especially in very dry years  Strong winds  Trees may fall down especially at front side of lake where exposed to strong wind and wave action and bank erosion  Trees inside the gallery forest are more protected  Wind may affect success of flowering and fruiting  Storm events  Trees may fall down especially at front side of lake where exposed to strong wind and wave action and bank erosion  Trees inside the gallery forest are more protected  Storms may affect success of flowering and fruiting

Table 6-3: Vulnerability matrix for gallery forest habitats

Impact Adaptive Threat Exposure Sensitivity Level capacity Vulnerability

High Temperature H M H H M

Increased rainfall in wet season H L M H M

Increased wet season water levels VH VH VH H VH

More irregular rainfall in dry M L M H L season

Longer period of dry season M L M H L

Increased P/PET balance in April M L M H L

Change and shift in events

Strong winds H M H H M

Storm events H M H H M

The gallery forests around Boeung Chhmar are particularly vulnerable to changes the water levels in the wet season and the depth and duration of the flood. Under climate change it is likely that expected that the wet season flooded area will increase slightly, but this may be moderated by the impacts of infrastructure development which will store water during the wet

77 season. The dry season flooded area extent under climate change is likely to be reduced, but with infrastructure development, the flooded area extent will increase. This will threaten the survival of much of the flooded forest of Boeung Chhmar. For other aspects of climate change the gallery forest habitat is less vulnerable, though increased temperature at the time of flowering and fruiting may reduce the fertility of seeds.

6.3.3 Mixed flooded shrubland with trees

The mixed flooded shrublands with trees would appear to be the least vulnerable of the Boeung Chhmar habitats, and indeed there may be an expansion of this habitat as the gallery forest area reduces under pressure from increased inundation or the grassland habitats become too deep, or damaged by fire, allowing invasion of shrubs, especially Mimosa pigra.

6.3.4 Flooded grassland

The summary of the vulnerability assessment for flooded grassland is as follows:

 High Temperature  Higher temperatures during growing wet and early dry season may bring forward maturation of grassland species  Over time there may be a shift towards more temperature tolerant species  Increase in temperature may also increase risk of fire, but fire in grassland is part of natural cycle  Increased rainfall in wet season  Increased rainfall will have little impact upon the growing conditions in the grasslands, which will already be becoming flooded  More secure start of monsoon in May/June will ensure early growth of grasses  Heavier rainfall in September may delay maturation of grass seeds  Increased depth and duration of inundation  There may be a shift in areas covered with grassland species towards taller shrubland species  With infrastructure development it is expected that the areas under grassland will remain more or less the same  More irregular rainfall in dry season  The lower rainfall in the dry season will have little impact upon grassland areas because growth mostly occurs during the wet season and during recession  Longer period of dry season  Unlikely that grasslands will be much affected by variability in length of dry season  Increased P/PET balance in April  Growth of grassland species in late dry season will be low and so impact of decreased moisture will be less important  Increased risk of fires in grasslands which will inhibit survival of trees and shrubs in the grassland, but not the annual grasses and herbs  Fires will tend to maintain grassland habitats

 Strong winds  Grasslands unlikely to be impacted by strong winds in April/May  Fires likely to be spread more rapidly by these winds, possibly into shrublands and gallery forests  Storm events  As with strong winds, grasslands are unlikely to be impacted by storm events, though areas of mature grasses may be flattened temporarily  Little impact upon the extent and species mix of grassland habitat

Table 6-4: Vulnerability matrix for flooded grassland habitats

Impact Adaptive Threat Exposure Sensitivity Level capacity Vulnerability

High Temperature M M M H M

Increased rainfall in wet M L M H M season

Increased depth and H H H H M duration of inundation

More irregular rainfall in L L L H L dry season

Longer period of dry L L L H L season

Increased P/PET H L M H M balance in April

Change and shift in events

Strong winds L L L H L

Storm events L L L H L

Grassland habitats appear to be quite resilient to changes in climate, with the highest temperatures occurring when the grasses and herbs have matured and seeded. There may be some changes in extent of the grassland areas especially at the deeper flooded grasslands, which may tend to evolve as flooded shrublands. Increased risk of fires in the dry season is part of natural grassland cycle and may control conversion to shrubland. There may be changes in the predominant species mix of the grassland, but the habitat will remain.

6.4 Vulnerability assessments of key plant species

6.4.1 Swamp forest trees – Barringtonia sp

The MRC wetlands and climate change study on Lower Stung Sen considered the vulnerability of Barringtonia acutangula, one of the keystone species in the flooded forests of the Tonle Sap. In that situation the vulnerability of the species was considered to be low

79 largely because of its high resilience to flooding and prolonged inundation and ability to grow in rocky and pebbly substrates in strong currents nearest the water’s edge. （ICEM，2012）

The species can establish itself in areas with only a brief exposure to drying. Flowering and fruiting occurs throughout the year. It responds to drought and increased temperature by shedding leaves to reduce evapotranspiration. When under water leaves are retained and photosynthesis continues for several months.

It is well adapted to living in areas that have prolonged inundation and is especially resilient to increased flooding. The trees are able to survive periods of drought and increased temperatures, though increased temperatures in the wet season may have inhibitory effects upon flowering, fruiting and seed setting.

6.4.2 Shrubs – Sesbania sesban

The Mekong ARCC study used Sesbania sesban as one of the indicator species for wetland NTFPs. That report found that Sesbania grows in a wide range of soils from loose sand to heavy clay. It is native to monsoonal, semi-arid to sub-humid regions with annual rainfall ranging from 500-2000 mm. mm. It grows best where periodic water-logging or flooding is followed by a progressively drier conditions. The plant does not require a large habitat: small clumps of Sesban occur in the wild in moist riverine areas and can be domesticated at edges of ponds and canals. The plant can disperse long distances by water: the ripe fruits and seeds are buoyant. (ICEM, 2014)

In terms of tolerance, it has outstanding ability to withstand waterlogging and is ideally suited to seasonally flooded environments. When flooded, it initiates floating adventitious roots and protects its stems, roots, and nodules with spongy aerenchyma tissue. It is common along streams, swamp banks, and moist and inundated bottomlands. S. sesban shows some tolerance to moisture stress and tolerates soil alkalinity and salinity to a considerable degree. The plant is resilient to drought. Re-sprouting from the rootstocks can occur easily when moist conditions return.

S. sesban is not threatened by human use: flowers are harvested for food and stems are harvested for fuel wood of low value. S. sesban is attacked by nematodes, insects, fungi, and viruses. The leaf-eating beetle Mesoplatys ochroptera can completely defoliate S. sesban, leading to mortality. Caterpillars, Hymenoptera, and stem borers are normally associated with S. sesban. Some potentially destructive root-knot nematodes have been recorded in India as associated with S. sesban.

Exposure to temperature is not an issue for S. sesban. The plant temperature comfort zone is between 18oC to 23oC (min 10oC, max 45oC). For rainfall exposure, as a tree legume, the plant is found growing in a very wide range of rainfall environments. Sesban is less tolerant to drier environments. When soil moisture drops below 12.5%, 55% of leaves will fall. As the plant shows excellent tolerance for inundation conditions, exposure to flooding is not an issue. The change of timing of the onset of the rainy season is likely to affect the flowering of the plants as it flowers at the onset of the rainy season in June-July. This is unlikely to affect the plants in Boeung Chhmar.

For extreme events, strong winds and storms will cause the stands to collapse but are unlikely to kill the plant. In terms of fire risk, in dry conditions the above-ground stems can be burnt but stands quickly recover when moist conditions return from seeds in the soils.

S. sesban has some good traits for adapting to adverse conditions:

 Water-impermeable seed coat enabling seed dormancy can help seed to wait out adverse conditions

 Provided there is flooded and moist areas, the plant will survive

 Populations are widespread; excellent tolerance of waterlogging conditions

 Individual plants live for 1.5 years with rapid establishment and early growth

 Seeds are carried long distances by water

It is considered that Sesbania sesban generally has a low vulnerability to climate change in Boeung Chhmar because the species has wide ranges of tolerance for heat, inundation, and drought. The changed conditions would not exceed these tolerance ranges. However, if other plants become stressed by temperature and decline, the additional pressure from human collection will increase. If climate change affects the Sesban pollinators, then pollination and fruit/seed setting may be reduced.

6.4.3 Shrubs – Mimosa pigra

The MRC case study of climate change and wetlands in Xe Champhone carried out a vulnerability assessment for Mimosa pigra, where the level of invasion was high (ICEM, 2012). This assessment shows that giant mimosa is a very hardy species that is tolerant of extremes of both flood and drought. It is spread by the seeds being carried by flood waters reaching new areas, and because it has no uses or natural enemies to keep populations under control, it tends to dominate and exclude other similar shrubs. It is to be expected that the climate changes expected in Boeung Chhmar with higher floods in the wet season will tend to enhance its spread. However, because it cannot survive in permanently flooded area, the increase in seasonally exposed areas due to the lower rainfall and increased drying in the dry season, may mean that the areas where it can survive may increase. Mimosa pigra has a low vulnerability to climate change and this will tend to increase its invasiveness.

6.5 Vulnerability assessments of key fauna

The vulnerability assessment sheets for the key species are presented in Annex 2. The summaries are presented below; these focus on the main exposures, sensitivities and adaptive capacities of these habitats and their overall vulnerability to specific climate changes and extreme events.

6.5.1 Fish

A comprehensive vulnerability assessment of the impacts of climate change upon capture fish species and aquaculture was carried out under the Mekong ARCC project for several provinces and ecosystems, including the Tonle Sap swamp forest (ICEM, 2013). The

81 assessment include detailed vulnerability assessments for a 30 indicator species of which 20 are likely to be found in Boeung Chhmar, including Channa striatus, Cirrhinus microlepis, Clarias batrachus, Trichogaster pectoralis, Mastocembalus armatus, Oreochromis niloticus (Aquaculture). The CAM matrices for these species are found in Annex 3. Although these assessments have been done for different climate change hotspots in the Lower Mekong Basin, the findings are also applicable to the conditions expected in the Tonle Sap. The main climate change threats considered were increase in temperature, increase/decrease in precipitation, increase/decrease in water availability, drought, flooding and storms and flash floods.

The general finding of the Mekong ARRC fisheries study was that:

1. Black fish tend to be less vulnerable to climate change because they are able to survive poor water quality conditions (low Dissolved Oxygen, low pH, high turbidity and high ammonia) 2. Black fish are able to withstand harsh dry season environments including high temperatures and anoxic conditions. 3. Their limited migratory habits make them less vulnerable to wetlands fragmentation 4. Most white fish species require higher water quality conditions in terms of Dissolved oxygen and alkalinity 5. They are more vulnerable to increased temperatures, especially at maturation and fry stages 6. They are more vulnerable to decreases in water availability e.g. in the dry season

Fish and other aquatic animals in the Tonle Sap have evolved to take advantage of the seasonal variation in water levels, surviving the harsh conditions through the dry season when water levels can be very low and to mature quickly and breed at the onset of the rains.

Critical time of year will be at the end of dry season when DO is low, temperature high and and when the strong winds blow to overturn the open waters, releasing poor quality water from the bottom, and causing large fish kills. This is likely to happen more frequently with climate change. Most fish species will be highly vulnerable to this threat of climate change, though it is not clear what will be the impact upon the populations of fish in Boeung Chhmar.

Summaries of the vulnerability assessments of particular species:

Channa striatus. A black fish found in a wide range of wetland environments, including rice fields, reservoirs and canals. It is considered to have a low vulnerability to increased temperatures, because the projected temperature rises are well within the tolerable range for this species. It is an air breathing fish, so Dissolved Oxygen levels are less important. It has low vulnerability to increased rainfall in the wet season, since this will allow easier access to the wider wetland areas around Boeung Chhmar. Flooding will also increase the inundated

82 area, providing additional breeding and feeding areas around the wetland, and will increase population numbers. In the dry season, the species would have a moderate vulnerability to the reduced rainfall which is likely to decrease the extent of inundated areas of the wetland, so this will tend to concentrate this species in the remaining areas of open water, with increased predation and fishing pressure. Generally a low vulnerability to climate changes expected in Boeung Chhmar.

Clarias batrachus.6 The walking catfish is a black fish species resident in Boeung Chhmar throughout the year. The increased projected temperatures are well within the range of this species, and it is tolerant of both high turbidity and low dissolved oxygen. In its natural habitats it is likely to have a low vulnerability to increased temperature, and will be able to survive in the conditions in the remaining open water refuges in the dry season. Its ability to “walk” means that it is able to move overland to more favourable pools as the wetland dries. During the wet season, increased rainfall and water availability, and increased extent of the inundated area will be beneficial for this species. It will be unaffected by flooding, though drought in the dry season will cause stress. Generally a low vulnerability to climate changes expected in Boeung Chhmar.

Trichogaster pectoralis. A non-migratory, small black fish, important for food security. It is known to be tolerant of a wide range of temperature, with an optimum temperature between 23 – 28 oC. It is considered to be moderately vulnerable to increase in temperature. It is a resilient black fish species able to withstand reduced rainfall and water availability in the dry season, provided that it has the remaining open water bodies as refuge. It is considered moderately vulnerable to reduced rainfall, but during drought conditions, as the refuges contract it will experience greater stress from reduced space, food and increased fishing pressure. With the rainfall increasing in the wet season, the rapid expansion of aquatic habitats will encourage its growth, maturity and spawning. Generally a low vulnerability to climate changes expected in Boeung Chhmar.

6 Note that for this species, the CAM vulnerability assessment was carried out for aquaculture in earth ponds.

Hemibagrus nemurus, red-tailed catfish. This catfish is found in many freshwater habitats, preferring large muddy rivers, with slow current and soft bottom. It can breed all the year round, but the peak of spawning will depend upon the location and weather. It does not migrate for long distances, but enters the flooded forests to spawn and young are usually seen in early August. In the Tonle Sap, largest numbers are seen as it returns to the rivers in November and December. It resides in deep pools in the mainstream and tributaries during the dry season.

In Boeung Chhmar, it will be entering the flooded forests at a time when the flood levels are highest, and temperature and water quality issues are of least concern. At other times of year it is unlikely to be resident in the shallow open water and wetland areas of Boeung Chhmar. It is considered to have low to medium vulnerability to the climate changes expected.

Oreochromis niloticus. Tilapia is an exotic species, introduced through escapes from fish culture. Table 6-5 shows the temperature ranges for different species of cultured fish, indicating that this species is particularly tolerant of higher temperatures with an optimum range between 30 – 32oC, and so will be unaffected by increased temperatures. It is also tolerant of low dissolved oxygen, though perhaps not as tolerant as the snakeheads and catfish. As with other resident species, it will be stressed by the reduced rainfall and more rapid drying of the wetland in the dry season, which will tend to concentrate the fish into the remaining pools, making them more susceptible to predation and fishing pressure. It will benefit from the increased rainfall in the wet season and flooding which will extend the inundated area for breeding and feeding. Generally a low vulnerability to climate changes expected in Boeung Chhmar.

Table 6-5 Optimum water temperature ranges for commonly cultured fish

in the Lower Mekong Basin

Source: Quoted in Mekong ARCC Fisheries paper

Cirrhinus microlepis, Small scale mud carp. This species is a white fish that moves into the wetland from Mekong mainstream and tributaries during the rainy season, breeding during June and July and with juveniles nursing in the floodplains, and leaving at the end of the wet season as the waters in the floodplain recede. It is herbivorous, consuming leafy plant matter and phytoplankton and also insects. It is recognized as a Vulnerable species in the IUCN Redlist. White fish tend to be less tolerant of higher temperatures than black fish, but this species will be living in the larger bodies of flowing water during the dry season, and so be less exposed to the lower water quality conditions experienced in Boeung Chhmar during the dry season. The increased water temperature in the wet season may affect the nursing juveniles more than the adults. During the wet season, the white fish move in to take advantage of the inundated wetland area, with the higher dissolved oxygen and overall improved water quality. Thus they will benefit from the increased rainfall, and larger extent of the wetland in the wet season. They may also benefit from the more reliable start of the rains in May. Overall, this species has medium vulnerability during its movement into Boeung Chhmar.

In summary, the black fish populations of Boeung Chhmar generally have a fairly low vulnerability to climate changes. They are adaptable, hardy species that have evolved to be able to cope with the long dry seasons when conditions are at their most stressful.

The white fish populations only enter the wetlands during the wet season when the generally higher rainfall, increased inundation and lower temperatures make the conditions acceptable and even beneficial for white fish populations. The populations may depend upon how climate change and other threats affect them outside of Boeung Chhmar in the dry season.

All fish species are likely to be highly vulnerable to the mixing of poor quality water at the end of the dry season, caused by strong winds acting upon very shallow water in the open waters of Boeung Tonle Chhmar.

6.5.2 Eel

Eels are considered separately from the other black and white fish, partly because the communities consider them differently and partly because they have different behavior patterns. True eels and swamp eels are generally very hardy species, being tolerant of poor water quality, and with an ability to move overland to find more suitable conditions. They are also able to hibernate living in holes in the mud during the dry season, emerging to be more active at the during the flood season.

The species considered here is Mastocembalus armatus, which is an eel-like fish, known as the zig-zag eel from its longitudinal dark brown zig-zag patterns on its skin. It forages at night feeding on benthic insects, worms and submerged plant material. It is usually found in rivers and streams with sand, pebble or boulder substrate, where it seldom leaves the bottom except when disturbed, and may remain partially covered by fine substrate. It is reported to occur in the Mekong mainstream with rocky bottoms during the dry season and move into canals, lakes and other floodplain areas during the flood season.

In terms of climate change vulnerability, the Mekong ARCC fisheries study carried out a vulnerability assessment, Mastacembalus armatus. The CAM matrix for this species is included in the Annex.

This species is more of a river species compared to the swamp eel, and does not have the same adaptive capacity in terms of it being able to move overland and burrow. Nevertheless, the species is tolerant of high water temperatures and low dissolved oxygen, and the projected increases in temperature are within the tolerance range of the species. For M. armatus the drying out of water bodies during prolonged dry seasons would render it moderately vulnerable.

Increased rainfall in the wet season, greater extent of the inundated area and flooding are likely to be beneficial for the species, providing both more habitat for the populations to expand into and larger populations of prey species.

The swamp eel can move away to find other remaining bodies of water, and it can burrow into the mud and survive. Its vulnerability would therefore be low.

6.5.3 Crustacea - Rice field Shrimp – Machrobrachium lanchesteri

Some of the important biological characteristics that may determine the resilience of M. lanchesteri to climate change include the following description taken from samples in Malaya (Johnson, 1968).

It is a good swimmer, with a light and somewhat compressed build and a relatively large abdomen and lives in fresh waters throughout its life cycle. It can flourish and breed under pond conditions. It is eurytopic with respect to most environmental factors, meaning that it can live under very varied conditions. It is a vegetarian and not cannibalistic under normal conditions.

Since M. lanchesteri can live in shallow habitats it has to be able to withstand exposure to rather high temperatures for periods of several hours. The full range of temperatures from which the species has been collected is 25.5°C to 36.0°C, which corresponds to the temperature range of aquatic habitats in southern Malaya. It does not appear to exhibit any behavioural response to increasing temperature. It is tolerant of a range of dissolved oxygen concentrations being capable of surviving in water with less than 25 percent oxygen saturation. It is most frequently found in waters with pH between 6.0 and 7.0 and there are no records from waters with pH below 4.9. The records for alkalinity give a similar picture to those for pH, surviving in the range of 0.150 mEq/l up to 2.80 mEq/l with the mean of 0.460 mEq/l.

The female carries the eggs until spawning. Studies on the breeding biology of M. lanchesteri in Myanmar and in Assam indicates that they breed throughout the year, but with peaks during the monsoon, especially in July to November, with fewer eggs being carried from thereafter. More than half of the eggs were still at an early stage of development for every month sampled. The incubation interval of the eggs was estimated to be less than one month, because of the presence or absence of eggs in the eyed stage during the period from February to March. (Phone, 2005)

The summary of the climate change vulnerability assessment for ricefield shrimp is as follows:

 High Temperature o Despite increased temperatures especially during the dry season, conditions are unlikely to cause mortality in the shrimps o Little impact upon breeding, which occurs throughout the year, though more during the monsoon, when temperatures are moderated  Increased rainfall in wet season o Additional water in wet season will not make much difference to shrimp populations o Increased water levels and flooding will extend shrimp habitat and increase numbers  More irregular rainfall in dry season and longer period of dry season o Impacts will be greater on shrimp populations if shallow ponds in floodplains dry out o Populations living in open waters will be less affected by drought conditions  Increased P/PET balance in April - Little direct impact upon shrimp populations  Strong winds may cause some mortality of shrimps in B. Tonle Chhmar after strong winds due to poor water quality, though this may not be noticed when many larger fish are dying  Storm events are unlikely to have any impact upon shrimp populations

Ricefield shrimps appear to be tolerant of adverse water quality conditions and have a relatively prolific and adaptable breeding cycle. Of the various climate change threats the shrimp populations will be most vulnerable to drought and the drying out of shallow floodplain pools in the dry season. Populations living in the open water bodies will be able to survive drought, but may be susceptible to higher temperatures and poor water quality during strong wind events in the late dry season. The vulnerability matrix summary for the rice field shrimp highlights the high vulnerability to more irregular rainfall expected in the dry season and the longer dry season expected in Boeung Chhmar.

Table 6-6 Vulnerability Matrix summary for Machrobrachium lanchesteri

Impact Adaptive Threat Exposure Sensitivity Level capacity Vulnerability High Temperature H M M H M Increased rainfall in wet season H VL M VH L More irregular rainfall in dry season H H H H H Longer period of dry season H H H H H Increased P/PET balance in April H VL M VH L Change and shift in events Strong winds H M H VH M Storm events L VL L VH L

6.5.4 Snails – Pila scutata and Pomacea canaliculata

The CAM matrix for the Golden Apple Snail was copied from the Mekong ARCC Fisheries report (ICEM, 2013) where the impact of climate change on the invasiveness of the species was assessed. The vulnerability of the ecosystem of the Mekong delta in Kien Giang to this invasive species was considered rather than the vulnerability of the species itself. The following comparison of the climate change vulnerabilities of Pila scutata and Pomacea canaliculata has been developed from a review of the differences in the physiology, reproductive behavior and response of the two species to environmental conditions, reported in a review of Ampullariid (Apple) snails as agricultural pests (Cowie, 2006).

Both species inhabit slow moving or stagnant water in lowland swamps, marshes, ditches, lakes and rivers. Both species are amphibious being able to spend substantial periods of time out of water breathing air. Both Pila and Pomacea can aestivate under adverse environmental conditions, e.g. during the hot dry season as the water bodies dry up. Aestivation consists of burrowing into the mud and closing the operculum to restrict water loss. Under natural conditions this may last for up to 3 months until the rains come, but under experimental conditions, aestivation periods longer than 1 – 2 years have been recorded in some species. Aestivation can take place at different depths in the mud, with Pila species tending to burrow up to 1 m deep into the mud. Pila species tend to have an anaerobic metabolism during aestivation and may experience considerable weight loss. Pomacea species tend to aestivate nearer the surface with aerobic respiration.

For most of these snail species the upper tolerance limit of water temperature is about 40oC. Cowie (2006) suggests that with P. canaliculata originating in more temperate climates, it has a slightly lower temperature tolerance than the native tropical species. The normal temperature tolerance range for P. canaliculata lies between 15.2o and 36.6oC. The projected increases in maximum temperature in the wet season are generally within this range, though the dry season maximum temperature comfort zone will exceed this slightly. Pomacea species may be able to regulate their body temperature during aestivation through evaporative cooling, up to air temperatures of 41oC. During the hot dry season experienced

88 in Boeung Chhmar, both species of snails will be able to avoid the higher and potentially lethal maximum temperatures projected for climate change, through aestivation. During the wet season, the temperatures are both lower and there is plenty of water, so the high temperatures are not expected to stress the snails.

Breeding in both snails tends to be seasonal, depending upon latitude, temperature and rainfall. Under the tropical conditions around the Tonle Sap the rainfall is likely to determine reproduction, with breeding and oviposition occurring from the start of the rainy season. Cowie (2006) has suggested that in the tropical regions of South East Asia, release from the seasonality of its natural range (based upon temperature) may be one of the reasons why P. canaliculata is so prolific. Rapid growth and breeding and hence a rapid succession of generations are permitted year round (or at last as far as water availability permits) leading to rapid population expansion and high population densities.

The eggs of Pomacea are laid on the stalks of vegetation above the water and are coloured pink or orange, whereas the eggs of Pila are colourless and deposited in depressions in the banks or mud made by the snails. There is a hypothesis that the brightly coloured eggs of Pomacea are a warning to predators that they are distasteful compared to the eggs of Pila. Eggs of both species will hatch within 2 weeks and the newly hatched snails fall or crawl into the water. The temperature threshold for normal maturation of snail eggs may be between 35 – 37oC. Above this temperature, the eggs may not develop normally.

The populations of these snails depend upon a number of factors, especially the availability of food and suitable habitat area, and the duration and intensity of the dry season. The increased rainfall and increased inundation area of the wetland will favour the rapid population growth and spread of the snails, as will flooding when it occurs. However, Pomacea canaliculata is known to be a particularly voracious eater in comparison to other snail species, and though it has its food preferences, e.g. rice plants, it is a generalist. Competition for food sources between the two species is likely to be a factor determining the population sizes.

The CAM analysis for Pomacea canaliculata in the Mekong delta supported the hypothesis that climate change would enhance the invasiveness of the Golden Apple Snail. However, in comparison to Pila scutata, both would appear to be well adapted to cope with a hotter and drier dry season, and both able to take advantage of the increased rains and larger wetland area in the rainy season. From the above comparisons it may well be the habitat requirement for permanent wetland area that determines the populations of Pila. On the other hand, it may be that the higher reproductive capacity and voraciousness of the feeding habits of Pomacea drive its invasiveness, rather than climate change.

6.5.5 Reptiles – Water snakes

The 2005 status review of the Biodiversity of the Tonle Sap Biosphere reserve (Davidson, 2006) notes that water snakes are known to breed in the swamp forests and short tree shrubland between August to November, i.e. late to end of wet season. Eggs have been seen and collected in September.

This paper also notes that “the watersnake harvest has two peaks, between July and August (wet season), and again in November-December (early dry season). The first and largest peak of the harvest coincides with the breeding of E. enhydris and the second peak occurs

89 just prior to the breeding seasons of many of the other species, as the water starts to recede. It is not known what effect this has on recruitment.

“The seasonal distribution and habitat use of watersnakes in the Tonle Sap is still very poorly understood. The highest catch success is achieved by hunting in the shallow edge of the lake, which can move up to several kilometres back and forth each year. Some of these species are closely associated to shallow-water edge habitats and mud-root tangle. Water snakes are not caught in open water at the height of the dry season, when water has receded from the forest (in March-April). This indicates that the snakes may remain in the forest; both E. enhydris and H. buccata have been found aestivating in the dry floodplain of the lake during this period, inferring a close year-round association with forest habitats.”

From a climate change vulnerability perspective the key period for the water snakes is the breeding period between August and November. During this period the mean maximum temperatures is projected to increase from a baseline of between 27 – 29 oC to between 30 - 32 oC, a potential increase of 4 deg C. This increase is projected for August (see Figure 5.7), although in September through October the difference appears to be about 2 – 3 deg C.

Unlike turtles and crocodiles in which the gender of the eggs and hatchlings is determined by environmental factors such as temperature, the gender of snake species is determined by the sex chromosomes (see next section). Thus the maximum temperature projections are not likely to be as critical to the populations of the Tonle Sap water snakes as to the turtles and crocodiles. Nevertheless this is a substantial rise in temperature and it is not known what physiological effects this will have either upon the adult snakes or the eggs and hatchlings.

During the dry season when temperatures are likely to rise even higher, the increases in mean maximum temperatures during March and April from a baseline of 31 – 32 oC to 34 - 36 oC by 2050 are also substantial (between + 2 – 4 deg C). It is expected that such temperature rises at the height of the dry season, may encourage the water snakes to aestivate more than the currently do. They are known to go into aestivation with a lower metabolic rate at times of high temperature and drought. This may make them more vulnerable to collection at such times.

The other aspect that should be considered in assessing the vulnerability of the water snakes is any change that may occur in their favoured habitats, namely the swamp forests and the short-tree shrubland. A consideration of the vulnerabilities of these habitats, shows that the gallery forests are expected to be under pressure and may shrink under a combination of climate change and infrastructure development upstream, whilst the short tree shrubland may expand into both the grasslands and the gallery forest areas. It is not considered that habitat changes induced by climate change are likely to make the water snakes more vulnerable.

Brooks et al (2007) warn that the water snake populations of the Tonle Sap are already declining under pressure from hunting and collection especially for crocodile farm feed. This is made worse because the peak snake collection season coincides with the breeding season, especially for E. enhydris, which has a relatively low fecundity. E.enhydris makes up a large proportion of the water snake harvest. (Brooks, Allison, & Reynolds, 2007)

6.5.6 Turtles

Two of the commonest turtle species are considered here - the Malayan snail eating turtle (Malayemys subtrijuga) and the Yellow headed temple turtle (Hieremys annandalii). The CAM assessments are taken from the vulnerability assessment carried out for the Beung Kiat Ngong Ramsar site in Lao PDR. In Boeung Chhmar the habitats associated with turtles include the inundated forest-scrub with numerous pools, which is considered the most important habitat for turtles during the dry season (Long 2003), particularly in areas with high numbers of fruiting trees (Sun Visal, WCS, verbally September 2005). Most turtle species are thought to breed in the dry season, when human disturbance and the risk of fire are highest; indeed, use of fire is reported as a method for hunting turtles in forest habitats in the floodplain during the dry season (Balzer et al. 2002).

Some species lay eggs in submerged substrates within ponds that later dry-out, others spend the dry season partially or wholly submerged in mud at the bottom of ponds that dry out. Both are susceptible to collection by professional hunters with dogs. Turtle nests have a variety of natural predators, including the macaques (locally numerous), rats (abundant) and some birds (e.g. coucals and corvids, both locally common).

The Malayan Snail-eating turtle is found in slow-moving bodies of water with muddy bottoms and lots of vegetation, such as marshes, swamps, rice paddies, and irrigation canals. It helps to control snail populations, which form almost its entire diet, though it also consumes earthworms, aquatic insects, crustaceans and small fish. It is preyed upon by monitors, and the young can be taken by large fish, snakes, wading birds, and crows.

It nests during the dry season, laying a clutch of four to six white, elongated eggs. After being incubated at 28 to 30oC for around 167 days, the young turtles hatch. Timing is thus critical so that the young hatch at the same time as the rains start in June and July, taking advantage of the availability of food and increases in the inundated habitat. Like other turtles, this species takes a long time to reach maturity; males mature after about three years while females are sexually mature at about five years.

The Yellow-headed temple turtle is a larger turtle that can grow to 60 cm across. It is herbivorous feeding on vegetation found growing in its aquatic habitat, as well as land plants that overhang the water and fallen fruits. Mating usually takes place between the months of December and January, after which female excavates a nest, into which a clutch of around four elongated, hard-shelled eggs are laid.

Turtles, in common with other reptile species, experience Environmental Sex Determination (ESD) such that the temperature of incubation of the eggs determines the sex of the hatchlings. Males tend to be selected when the incubation temperature lies between 28 and 30oC, whilst females develop above and below this temperature range. The position of the egg in the nest, and the depth of the nest below the soil surface affects the incubation temperature. One of the serious climate change threats that has been identified for turtles is that with increasing temperatures, the proportion of males in the population will decrease, potentially completely. (Loudon, 2012). The pivotal or “switch-over” temperature can be as little as 1 deg C, so small increases in incubation temperature can completely change the sex ratio of a clutch.

Turtles are ectothermic animals with the body temperature dependent upon the environmental conditions. This means that all their behavior, growth and metabolism will be dependent upon the temperature of air and water. Many turtles during the hot dry season will spend much of their time at the bottom of pools, where it is cooler, to avoid the heat. However, it may be that high temperatures during the early development of the young turtles also leads to behavioural change. Researchers in Queensland, Australia have found that eggs of the Mary river turtle incubated at higher temperatures tend to produce hatchlings that showed reduced swimming ability and a preference for shallower waters. This means that the survival chances of turtles incubated at higher temperatures may be reduced, since deeper water, where their food supply is found, provides the young turtles with protection from predators. Young turtles with poor swimming abilities which linger near the surface are unable to feed and are very likely to get picked off by birds. (Society for Experimental Biology, 2011)

The female turtles may show some adaptive capacity to alter the depth of the nests depending upon environmental conditions, but research with a marine turtle (Chrysemys picta) did not show consistent results to indicate that this was a reliable mechanism for adaptation to climate change. The research found no effect of nest depth on six parameters of incubation regime, nor on resultant offspring survival, size or sex ratio. However, deeper nests produced hatchlings that weighed less, and were faster at righting themselves and swimming, than hatchlings from shallower nests. (Refsnider, October 2013)

A CAM matrix assessment was carried out for both turtle species included in Annex 2, of which the summary is shown below. The major climate change threat to turtles is increased temperature, especially during the period of nesting and incubation of the eggs which takes place during the dry season, when temperatures are highest. Increased temperatures can affect the sex of the hatchlings and skew the sex ratios of populations, with greater numbers of females being produced at higher temperatures. There is little adaptive capacity available for turtles to adjust this. Also increased temperatures have been shown to affect behaviour of turtles, with slower swimming speeds and tendency to swim closer to the surface for those hatchlings incubated at higher temperatures.

The lower rainfall and higher evapotranspiration in the dry season is likely to cause a shrinkage of the wetland habitats with smaller wetted areas and shallower pools making the turtles easier to catch, i.e increased vulnerability at this time. When the rains come and expand the wetted area again, the turtles are likely to benefit from the expanded area and higher availability of food sources. Increased intensity and frequency of storms and flooding should not have any effect upon the turtle populations.

Table 6-7 Vulnerability assessment matrix for both species of turtle found in Boeung Chhmar

Adaptive Threat Exposure Sensitivity Impact Level capacity Vulnerability Increase of temperature especially at end of dry season H VH VH L VH Irregular distribution of rainfall in dry season, including H H H M H drought Increase in rainfall in wet season H L M H M Change and shift in events Increased frequency and intensity of storms M VL L H L Increased risk of Flooding L VL L VH L

6.5.7 Large water birds

The vulnerabilities of the large water birds, such as the storks, adjutants and Asian Open bill are not systematically assessed here. The vulnerability of the large water bird populations will be dependent upon the climatic conditions at the time of breeding and incubation, but this has not been considered since nesting occurs in the bird colonies at Prek Toal, rather than in Boeung Chhmar. However these birds are an important part of the ecosystem in Boeung Chhmar since they come in large numbers in March and April to feed taking advantage of the rich food sources to be found at Boeung Chhmar at the end of the dry season. The low water levels at that time of year make fish, snails and other aquatic animals easier to catch. It is important because the juvenile birds need this source of food to complete their growth to maturity.

Thus the critical time for the ecological relationship between the large water birds and Boeung Chhmar will be at the end of the dry season. The most important factor is likely to be the impacts of climate change upon food availability at this time, and hence the populations of the food organisms. If these food sources decline in the future due to the influence of climate change, then the large water bird populations are likely to decline as well.

6.5.8 Mammals

The vulnerabilities of the mammals such as otters, macaques and silver leaf monkey have not been systematically assessed here. As with the large water birds, the impact of climate change upon the availability of fish as food for the otters is likely to be an important factor, though with the already low otter populations, this may not be critical.

7 Vulnerability of livelihood activities in Boeung Chhmar

This vulnerability assessment has focused on the habitats and flora and fauna of Boeung Chhmar, which constitute the principal natural resources upon which the communities that live within the Ramsar site depend. The vulnerabilities of their livelihoods depends upon the sustainability of these natural resources.

A summary of the natural resource vulnerabilities to climate change is shown below in Table 7-1. This can guide the assessment of impacts upon the livelihood activities.

7.1 Fishing

Fishing is the principal livelihood activity for all the communities living in and around Boeung Chhmar Ramsar site. The fish catch is either sold fresh or processed, used for domestic consumption of used as a food for fish raising. Processing may include drying, smoking, fermenting into Pra hoc. The communities have few other income generating activities, having no rice fields, and limited livestock, so they are highly dependent upon the fish stocks. Any changes in fish populations and species distributions as a result of climate change is likely to have an impact upon the livelihoods of these communities.

From the above vulnerability summary, the black fish, which make up the bulk of the fish stock, are resident throughout the year, especially in the dry season, are less vulnerable than the white fish, which come into Boeung Chhmar to breed in the wet season when water levels are high, and then move out again to dry season refuges. The critical time for the black fish therefore is at the end of the dry season when water levels are low and the risk of strong winds churning up bottom of the open water with poor water quality. Despite their resilience against poor quality water, these events result in massive black fish kills. In the short term these represent a bonanza for the fishermen, especially now that the commercial fishing lots have been abolished. In the longer term if climate change results in low water levels and increased frequency of strong winds in April/May, such fish kills may have an impact reducing the overall population size of black fish in Boeung Chhmar. This would have serious implications for the livelihoods of the fishing families.

The main white fish populations come into Boeung Chhmar during the wet season, and increased water levels and extent of the flooded area may increase the possibilities for white fish breeding and growth. They are unlikely to be large numbers of white fish killed in the late dry season. However, other climate change factors elsewhere in the dry season refuges may reduce the population size available to enter Boeung Chhmar. White fish tend to be more sensitive to poor quality water and increases in temperature, than black fish. Habitat changes in Boeung Chhmar resulting from climate change (reducing areas of gallery forest, reducing areas of grassland and increasing areas of shrubland, especially with Mimosa pigra invasion, may alter the availability of breeding habitats for some species. Reducing populations of white fish in the wet season is likely to have implications for livelihoods of communities living in Boeung Chhmar.

Table 7-1 Summary of climate change vulnerabilities of components of the Boeung Chhmar ecosystem

Ecosystem Critical climate change threat Impact Implications for livelihoods Critical vulnerability component

Dry season Wet season

Habitat

 Open water  Increased temperature, At end of longer and drier Release of poor quality water at end  Decreased rainfall in dry dry seasons, there will be of dry season likely to cause large season and longer dry less water available and the fish kills. If this occurs more season open water will become frequently, this will have a longer  Strong winds at end of dry even shallower. Strong term negative impact upon fish season winds at end of dry season populations, and changes in fish likely to become more species distribution. VH H frequent and cause overturn of open waters Communities will harvest the fish and release of poor quality killed, and this will be a short-term water. This will be made bonus for the fishers worse if water abstraction in the Stung Staung for dry season irrigation minimizes the flow to the open water

 Gallery forest  Increased wet season water Increased water levels in Gallery forests are important areas levels Tonle Sap will tend to put for spawning of fish, and for  pressure on gallery forests protection of the edges of the and reduce their area at the Boeung Chhmar against wind. If M VH water front side. They may flooded forest area is reduced, there be able to expand into may be implications for fish flooded shrubland, but not populations. certain. Effects may be compounded by changes in flows in Mekong due to

Ecosystem Critical climate change threat Impact Implications for livelihoods Critical vulnerability component

Dry season Wet season

infrastructure development

 Seasonally  Increased temperatures Grassland habitats are Little implication for livelihoods flooded  Increased wet season quite resilient. Highest grasslands rainfall temperatures occur when  Increased depth and grasses have seeded. Fires duration of inundation are part of natural cycle for  Increased P/PET balance in M M grasslands. May be some April redistribution of grassland  Increased risk of fire species Deeper areas may be invaded by shrubs especially Mimosa pigra

 Flooded Low threats Least vulnerable of the Little implications for livelihoods shrublands flooded habitats. May be an L L expansion of shrubland into gallery forests and into grasslands

Species - plants

 Barringtonia  Increased wet season water Well adapted to areas that Little implications for livelihoods acutangula levels have prolonged inundation  Increased temperatures L M and resilient to increased flooding. Increased temperatures during flowering and fruiting may

Ecosystem Critical climate change threat Impact Implications for livelihoods Critical vulnerability component

Dry season Wet season

affect fertility of trees.

 Sesbania Low climate threats Sesbania is very resilient, Flowers are collected as vegetable sesban because has wide for domestic consumption. Climate L L tolerance ranges for heat, change unlikely to affect this inundation and drought

 Mimosa pigra Low climate threats Mimosa is also very No really effective way of using or resilient. There may be controlling mimosa has been found. some increased invasion The bushes are difficult to penetrate L L into grasslands and and have sharp spines that catch degraded flooded forest fishing gear. Increased spread of areas. mimosa likely to hinder fishing activities

Species - animals

 Black fish Decreased water availability in There may be large fish Large fish kills may be a bonus for dry season, lower water levels kills in the open water due fishers in the short term. to poor quality water M L Strong winds churn up open release in late dry season. More frequent fish kills every year water and decrease water Black fish more resilient could reduce populations of resident quality than white fish fish

 White fish  Decreased water availability White fish less likely to be There may be an increase in white in dry season, lower water resident in the dry season, fish coming into the Boeung Chhmar levels H M but would be more with higher water levels, with larger  Strong winds churn up open vulnerable to poor quality populations. This would be beneficial water and decrease water water release for fishers. quality

Ecosystem Critical climate change threat Impact Implications for livelihoods Critical vulnerability component

Dry season Wet season

 Increased water levels in Wet season water levels Any remaining white fish at end of wet season increasing would be likely dry season likely to be killed off if  Increased temperatures to be favourable for white poor water quality is released by fish spawning, though strong winds temperature increases might become a problem

Uncertain about CC impacts on white fish in other parts of river basin in dry season refuges

 Eels Decreased water availability in Eels are very resilient and Eel populations will probably remain dry season, lower water levels can move overland to more similar and so there should be no favourable conditions, and livelihood implications for fishers M L Strong winds churn up open can hibernate in muds till catching this species water and decrease water the beginning of wet quality season

 Rice field  More irregular rainfall in dry Rice field shrimps tolerant Fishers catching rice field shrimps shrimp season of adverse water quality, should not be affected, though  Longer period of dry season with relatively prolific and catches may decrease in early wet  Increased temperature adaptable breeding cycle. season, when the floodplain pools fill Drying out of pools in up with water again, with fewer stock  Strong winds H L floodplain will be a problem, to replenish the populations and populations living in open water areas may be susceptible to strong wind events

Ecosystem Critical climate change threat Impact Implications for livelihoods Critical vulnerability component

Dry season Wet season

 Water snakes  Increase in temperature Water snakes breeding Peak water snake harvest coincides during dry season season is in late wet with breeding season. Climate  Increase in temperature season. Temperature change may add further stress to an during breeding season increases may cause already declining population. (wet season) H H physiological stress. Unsustainable harvesting of water In dry season, water snakes with climate change is likely snakes may aestivate more to lead to further collapse of because of higher populations and this source of temperatures and drought livelihoods

 Turtles  Increase in temperature at Increases in temperature Falling populations of turtles, end of dry season may affect the fertility and increased time required for hunting  Irregular rainfall in dry sex ratio of eggs and and collection. Likely elimination of season hatchlings, leading to turtle populations in the longer term. VH L increased pressure upon populations already stressed from overexploitation

 Apple Snails Increased temperature, Snails able to avoid hotter Competition between native apple especially in the dry season and drier conditions snails and Golden Apple snail likely through aestivation. Wet to favour the alien species, but season temperatures less probably not related to climate M L of a problem. Rapid growth change. Increase in Golden Apple and breeding leads to snail numbers likely to be a problem population expansion and for rice farmers around Boeung densities especially for Chhmar, but not in the Ramsar site. Golden Apple snail.

Ecosystem Critical climate change threat Impact Implications for livelihoods Critical vulnerability component

Dry season Wet season

 Large water Increased temperatures during Effects of climate change If large water bird populations decline birds the breeding season (at Prek upon food species for large and no longer visit Boeung Chhmar, Toal) water birds will be the the opportunities for developing critical factor, especially in ecotourism at the site will diminish. M L March, April, May for Boeung Chhmar. Increase in golden apple snails will favour Open Bill storks.

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7.2 Fish raising

Some of the fish caught are used as food for fish raising activities. Typically snakehead and catfish are raised in cages underneath the floating houses. Unlike the natural populations of such fish, which are seen as relatively resilient to climate changes, fish stocked in cages are likely to be more vulnerable. This results from the high density of the fish kept in the cages which puts them at higher stress and therefore more vulnerable to increases in water temperature and lowered water quality. Increases in temperature also increases the risks of outbreak of disease, which can quickly wipe out the entire stock of caged fish.

The Mekong ARCC fisheries study also assessed the vulnerability of aquaculture species, including snakehead and catfish in their climate change hotspot provinces (ICEM, 2013). That study only considered cage culture of carps in Khammouan, and it noted the vulnerability of the system to decreases in water availability, flooding, storms and flash floods. In other assessments in Mondulkiri and Gia Lai, intensive and extensive pond culture of catfish and tilapias also showed similar vulnerabilities. In Boeung Chhmar, the increased frequency of flooding, storms and flash floods is unlikely to be an issue for cage-cultured snakeheads and catfish, since they are not located in the mainstream of a river, and the cages are designed for high water levels. Increasing temperatures and poor quality water especially if the bottom muds around the fish cages are stirred up at the end of the dry season are likely to be the critical climate change concerns.

7.3 Fishing supporting activities

There are a number of livelihood activities that support fishing and fish raising. These include fish processing, boat and equipment maintenance and small businesses selling fishing nets and equipment and other household goods. All of these are highly dependent upon the success of the fishing sector. If the fish stocks decline as a result of climate change, so the fishing supporting activities will be affected and will be as vulnerable as the fishing itself.

7.4 Water supply

Whilst the communities in Boeung Chhmar are surrounded by water, the supply of water for drinking is a concern, because of water quality around the houses. Toilets discharge directly into the water, while fish processing and food wastes, caged fish food and fish excrement are disposed of in the water, and all contribute to lowering of the water quality. Water taken directly from the open water around Boeung Chhmar is unsuitable for human consumption, and would lead to health problems if used for drinking. Traditionally, local people directly use water from the lake for their daily water consumption, without treatment systems. Some households drink boil water as they are concerning about their family health. In addition, it has been noticed that the quality water used for bathing and washing can give rise to skin diseases, especially early in the wet season.

With climate change projections, the availability of good quality water for drinking will continue to be an issue. It is also likely that water quality issues in the late dry season and early wet season may well be increased with higher water temperatures and lower water levels, so that water used for bathing and washing may cause more skin disease. The increased temperatures and relatively high eutrophic level of the water is likely to increase the risk of algal blooms, which are often the cause of such skin disease.

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7.5 NTFP collection

Other aquatic plants and animals that are collected include:

 Sesbania – flowers collected for food, and the stems are used as floats for fishing gear and house floatation. The assessment for Sesbania shown above indicates that it has a low vulnerability to climate change, and so this source of NTFP is likely to remain available in the future.  Rice field shrimps – these are collected and provide a valuable source of income. The vulnerability assessment indicates the critical time may be at the end of dry season when the floodplain pools dry out, although the rapid breeding and growth of the species in the wet season may counter any losses. This source of NTFP is unlikely to be seriously impacted by climate change  Snails - It is expected that there will be a population shift towards greater populations of Golden Apple snail at the expense of the native apple snail, but this is not directly attributable to climate change. Golden Apple snails are collected and eaten, but the native species are preferred. This may increase the spread of the alien species and make the native species become rarer. Both species are considered to be equally resilient to climate changes.  Water snakes – The water snake populations are already declining due to unsustainable harvesting. Climate change may increase the physiological and reproductive stress on the water snakes and the combination may destroy the sustainability of the water snake harvest as a livelihood source.  Turtles – turtles are highly prized and their populations are already under pressure from over collection. It is expected that climate changes, especially increased temperatures during the dry season, when the eggs are laid, may cause gender shifts in the population. Such impacts are likely to have serious implications for the availability of turtles as a livelihood source.

7.6 Ecotourism

Ecotourism is not yet developed for Boeung Chhmar. The main attraction are the large water birds coming to feed in the wetlands in March – May. If climate change affects the food sources for the large water birds, then the birds may not frequent the Ramsar site to the same extent, but look for their food elsewhere. With fewer large water birds visiting, the attractiveness of the site to bird watchers will decrease and the potential for developing ecotourism will be lost.

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8 Conclusion

It is clear from the above discussion that the habitats and associated species in the Boeung Chhmar Ramsar site demonstrate a very varied response to the projected changes in climate. Some habitats are relatively resilient and may even expand their areas at the expense of less resilient habitats, e.g. the shrublands expanding into the grasslands and potentially gallery forests. Some species are particularly resilient especially the shrubs such as Sesbania and the invasive Mimosa pigra. It is expected that the latter will be one of the winners as climate change progresses.

The black fish species are generally quite resilient, but are expected to become more vulnerable to the poor quality water releases caused by strong winds over the open water. The open water habitats would appear to be particularly vulnerable at the end of the dry season. This impact is likely to be made worse by continued abstraction of water for dry season rice farming in the upper catchment of the Stung Staung, which effectively stops the flow of water in the dry season into Boeung Chhmar.

White fish species are less resilient to higher temperatures and poor quality water but really only enter Boeung Chhmar during the wet season, when there is plenty of good quality water. However, climate change stresses on the dry season refuges for white fish may be significant, although not considered here, and these may cause declines in white fish populations.

Fishing is almost the main livelihood activity for the communities living in Boeung Chhmar and thus there is an additional emphasis upon the vulnerability of fish populations. Other species such as water snakes and turtles, which provide a lucrative bonus when they are collected, have been seen to be highly vulnerable, and these species are already under severe hunting pressure. With climate change the populations of these species may not be sustainable as a livelihood source.

The arrival of the large water birds in March/April for which Boeung Chhmar is a recognized feature and tourist attraction may also be threatened by climate change, even before the ecotourism is developed. The birds come to feed on the fish, snails and other aquatic resources, and if these decline or access becomes more difficult for the birds, then this phase of their annual lifecycle is also likely to be vulnerable.

Looking ahead to adaptation planning, some of the key features to manage and protect in Boeung Chhmar include:

 Ensuring adequate dry season flows of the Stung Staung and Stung Chikreng to maintain a positive inflow into the Ramsar site and especially into the open water areas. This will help to maintain water levels in the open waters at the end of the dry season and reduce the risks of strong winds churning up the waters and releasing poor quality water, and increasing the massive fish kills.  Reducing the pressure on the gallery forests, through management of tree cutting, and possibly replanting efforts in the back side of the gallery forest areas bordering the Tonle Sap  Reducing harvesting pressure on vulnerable groups such as the turtles and water snakes

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 Managing the spread of alien species such as Mimosa pigra and Golden Apple Snail. For the latter, encouragement and protection of predator species such as Open bill storks should be promoted.  Provision of good quality drinking water for the communities, so that they are not directly reliant upon water from the creeks and open water.

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Annexes

Annex 1: CAM matrices of the key habitats

System – Boeung Chhmar 1. OPEN WATER

Threat Interpretation of threat Impact Summary

Exposure Sensitivity Impact Level Adaptive capacity Vulnerabili ty Change and shift in written description of how the refer to table Written explanation of what the impact is, and why it was refer to table regular climate threat relates to the asset scored (high, med, low) High Temperature  Increase of 2 – 3 deg C in VH7 VH8 VH  Substantially increased water temperatures during the L9 VH max temp. throughout the dry season year.  Increased evapotranspiration from water surface  Maximum temp range in during dry season March to April reach 33-36 C  Dissolved oxygen of the water will decrease with  Max temps up to 42 – 43 C increased temperature  Number of hot days increases  During wet season the temperatures are lower overall, from 11 to 51 days over 35 C there is more water and deeper water and the impacts of increased temperature will be less. Increased rainfall in  Increases by c.10% in wet VH VHV  Water levels in B Chhmar will rise faster in early wet H11 H wet season season 10 H season, but not perhaps as fast as Lower Stung Sen  Throughout all months of wet because catchment is half the size

7 There is no cover for the open water and the increases in temperature will reflect increase in air tempertaure 8 In March/April.May, the water is very shallow and the whole water column will increase more than when it is deeper. 9 The only adaptive capacity available to the open water is through evaporation t moderate the increase in temperature and this depends upon the volume of water available. In April/May this volume is relatively low 10 Increases in rainfall in St Chikreng and St Staung will increase water levels in B Chhmar at beginning of rainy season, followed by increased rainfall in wider Tonle Sap basin 11 Open water can absorb increased rainfall by raising water levels during wet season quite easily.

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season, but up to 12%  Sediments in B Chhmar mainly from two rivers rather increase in September than from Tonle Sap  Rainfall over the Tonle Sap catchment will be more important for 2nd rise in water level  Backwater from Mekong into Tonle Sap and into B Chhmar gives the 3rd rise and biggest rise in water level More irregular rainfall  Slight increase overall of VH VH  Reduced water levels in open water in dry season VL12 VH in dry season about 2.5% in dry season  Increased abstraction of water for dry season rice rainfall upstream which will add to falling water levels,  But decreases in Jan, Feb, including backflow from B Chhmar up into St Staung April, and bigger increase in ground water early May.  Water remains stagnant in B Chhmar  Drier in most of dry season  Water levels very shallow (less than half metre at moment) Longer period of dry  Community perceptions that  Water level remains low for longer maybe for 1 – 2 season rainy season start occurs later weeks before starts rising in early wet season in May or early June  In combination with increased temperatures, dissolved oxygen of remaining water will be lowered Increased P/PET  More evapotranspiration in  Less water available in the open water, water levels balance in April the dry season compared to falling in late dry season, especially in April precipitation especially increasing in April Change and shift in events Strong winds . More strong winds in April VH VH VH  Water temperature is very high, sediments and poor VH15 VH and May 13 14 quality water are churned up and mixed with water  Massive fish kills especially of white and grey fish  Blackfish seem less sensitive Storm events  Increased frequency and VH M16 VH  Storms will tend to churn up the water in the lake VH17 H

12 No recharge of water levels from catchment 13 Strong winds blow from east in April May, no protection from trees, so high exposure for open water 14 At this time the water level is very low and shallow, so greater opportunity for mixing and stirring up sediments 15 Effects of strong winds are worse if the dry season has been longer and with less rainfall, and water level is low, e.g. 2012 and 2013 16 Storms have little impact upon open water apart from adding water and increasing water levels 17 Open waters have quick recovery from impacts of storms

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intensity of rainfall increasing turbidity and mixing of water at different  Increased frequency of 80 levels mm events in one day from 7  Risks for fishermen in open boats per year to 11 per year

System – Boeung Chhmar

2. GALLERY FOREST

Threat Interpretation of threat Impact Summary

osure

Exp Sensitivity Impact Level Adaptive capacity Vulnerabili ty Change and shift in written description of how the refer to table Written explanation of what the impact is, and why it was refer to table regular climate threat relates to the asset scored (high, med, low) High Temperature  Increase of 2 – 3 deg C in H18 M19 H  Increased evapotranspiration from leaves due to high H20 M max temp. throughout the temperatures in late dry season, this is when the leaf year. cover is highest. (trees lose leaves in July as they get  Maximum temp range in flooded. March to April reaches 33-36  New leaves come in January, Flowers in April, C fruiting in early rainy season  Max temps as high as 42 –  Seeds dispersal in July. 43 C  High temperature may reduce growth and reduce the  Number of hot days fertility of seeds, because a lot of energy used for increases from 11 to 51 days evapotranspiration over 35 C  Terminalia (Ta Ue) is seen as most vulnerable species because of lower density than other species and high demand for firewood Increased rainfall in  Increases by c.10% in wet H L21 M  Early rainfall and run-off from St Staung and H M wet season season Chikreng important for rise in water levels in May

18 Some protection in middle of gallery forest to high temperatures due to forest cover 19 Tree species have wide range throughout India and Australia and have wide tolerance to extremes of temperature 20 High adaptive capacity esp riang. Because of seeding dispersal patterns, bark water content, and regeneration after fire 21 Gallery forest is not dependent upon rainfall for moisture, but from ground water

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 Throughout all months of wet June season, but up to 12%  More important are water levels from Mekong increase in September backflow which will determine the extent depth of the flood Increased wet  Increase in average year VH VH23 VH  There will be a tendency to lose gallery forest at H24 VH season water levels water levels by about 0.5 the Tonle Sap shore line and gain it at the m22 expense of flooded shrubland More irregular  Slight increase overall of M L25 M  Risk of forest fire likely to increase under drier H26 L rainfall in dry about 2.5% in dry season conditions season rainfall  Riang and Phthuol more resistant to fire than Ta  But decreases in Jan, Feb, ue April, and bigger increase in early May.  Drier in most of dry season Longer period of dry  Community perceptions  As above season that rainy season start occurs later in May or early June Increased P/PET  More evapotranspiration in M L M  May have impact upon flowering and fruiting H27 L balance in April the dry season compared success especially in very dry years to precipitation especially increasing in April Change and shift  in events Strong winds . More strong winds in April H M28 H  Trees may fall down especially at front side of H M and May lake where exposed to strong wind and wave H29 H action and bank erosion

22 From Arias et al (2012) 23 Gallery forest distribution is very dependent upon length and depth of inundation 24 High adaptive capacity in terms of ability to reseed areas at back side of gallery forest with lower inundation rates 25 Low sensitivity of gallery forest to rainfall – more dependent upon ground water which is abundant 26 High adaptive capacity because of resistance to fire and tendency to regenerate after fire 27 Trees are long lived and able to take advantage of good years for regeneration 28 Trees are quite resilient to strong winds, only the weaker rooted ones that will fall down

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 Trees inside the gallery forest are more protected  Wind may affect success of flowering and fruiting Storm events  Increased frequency and  As above intensity of rainfall  Increased frequency of 80 mm events in one day from 7 per year to 11 per year

System – Boeung Chhmar

3. FLOODED GRASSLANDS

Threat Interpretation of threat Impact Summary

29 Flowering is more sensitive to high winds 30 There is no tree cover to moderate the increases in temperature, but low vegetation may provide some cover 31 Highest temperatures occur at end of dry season when grasslands will have finished annual cycle 32 Most plant species in grassland are annuals and can withstand some years of very high temperature 33 Grassland species mix may change but the overall habitat will remain

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 Number of hot days increases from 11 to 51 days over 35 C Increased rainfall in  Increases by c.10% in wet M34 L M  Increased rainfall will have little impact upon the H M wet season season growing conditions in the grasslands, which will  Throughout all months of wet already be becoming flooded season, but up to 12%  More secure start of monsoon in May/June will ensure increase in September early growth of grasses  Heavier rainfall in September may delay maturation of grass seeds Increased depth and  Increased rainfall and back H H35 H  There may be a shift in areas covered with grassland H M duration of inundation flows from the Mekong will species towards taller shrubland species tend to increase the extent of  With infrastructure development it is expected that the flooding but this may be areas under grassland will remain more or less the moderated by impacts of same infrastructure in basin More irregular rainfall  Slight increase overall of L L36 L  The lower rainfall in the dry season will have little H L in dry season about 2.5% in dry season impact upon grassland areas because growth mostly rainfall occurs during the wet season and during recession  But decreases in Jan, Feb, April, and bigger increase in early May.  Drier in most of dry season Longer period of dry  Community perceptions that L37 L38 L  Unlikely that grasslands will be much affected by H39 L season rainy season start occurs later variability in length of dry season in May or early June  Projections show that monsoon is more likely to start in May/June

34 10% increase in wet season rainfall, but earlier start to rainfall will tend to encourage early growth 35 Areas of grassland will experience depths and duration of flood that disadvantage some species 36 During the dry season, most of the growth of grassland will be completed, 37 Disagreement between perceptions and projections, probably there will be greater variability 38 Assume that extent of growth and survival of grassland species is not dependent upon when the monsoon starts, but that there is enough water when it start 39 Grassland species have adaptive capacity to germinate and start growth when the monsoon arrives, even if it is late

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Increased P/PET  More evapotranspiration in H L40 M  Growth of grassland species in late dry season will be H M balance in April the dry season compared to low and so impact of decreased moisture will be less precipitation especially important increasing in April  Increased risk of fires in grasslands which will inhibit  Increasing risk of fire survival of trees and shrubs in the grassland, but not the annual grasses and herbs  Fires will tend to maintain grassland habitats Change and shift in  events Strong winds . More strong winds in April L41 L42 L  Grasslands unlikely to be impacted by strong winds in H L and May April/May . May increase spread of fire  Fires likely to be spread more rapidly by these winds, possibly into shrublands and gallery forests Storm events  Increased frequency and L L L  As with strong winds, grasslands are unlikely to be H L intensity of rainfall impacted by storm events, though areas of mature  Increased frequency of 80 grasses may be flattened temporarily mm events in one day from 7  Little impact upon the extent and species mix of per year to 11 per year grassland habitat  Most likely to occur late in wet season

40 Growth of grassland species will be ending in March, April and so reliance upon soil moisture is less important 41 Grasslands relatively protected from strong winds by surrounding shrubland 42 Grasses at this time of year have matured and seeded and being blown over by the wind does not really matter to the species

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Annex 2: CAM matrices of selected species

System – Boeung Chhmar

4. RICEFIELD SHRIMPS – MACHROBRACHIUM LANCHESTERI

Threat Interpretation of threat Impact Summary

Exposure Sensitivity Impact Level Adaptive capacity Vulnerabili ty Change and shift in written description of how the refer to table Written explanation of what the impact is, and why it was refer to table regular climate threat relates to the asset scored (high, med, low) High Temperature  Increase of 2 – 3 deg C in H43 M44 M  Despite increased temperatures especially during the H45 M max temp. throughout the dry season, conditions are unlikely to cause mortality year. in the shrimps  Maximum temp range in  Little impact upon breeding, which occurs throughout March to April reach 33-36 C the year, though more during the monsoon, when  Max temp up to 42 – 43 C temperatures are moderated  Number of hot days increases from 11 to 51 days over 35 C Increased rainfall in  Increases by c.10% in wet H46 VL M  Additional water will not make much difference to VH48 L wet season season 47 populations of shrimps  Throughout all months of wet  Increased water levels and flooding will extend shrimp season, but up to 12% habitat and lead to larger populations increase in September  Higher flood levels by about 10%

43 Water temperatures are likely to be moderated compared to air temperatures, except in small and shallow ponds, several degrees below mean max. air temperature 44 Shrimps appear to be quite tolerant of high temperatures 45 Shrimps have the ability to adapt behaviour to suit conditions, they may shift peak breeding period slightly 46 Rainfall and water levels in wet season in B. Chhmar will be significantly increased 47 During wet season, there is enough water for shrimps to expand into the floodplain and rice fields and multiply. Additional water will not make much difference 48 Shrimps can adapt populations and breeding cycles easily to changing water levels in the wet season

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More irregular rainfall  Slight increase overall of H H49 H  Impacts will be greater on shrimp populations if the H50 H in dry season about 2.5% in dry season shallow ponds in the floodplains dry out rainfall  Populations living in open waters will be less affected  But decreases in Jan, Feb, by drought conditions April, and bigger increase in early May.  Drier in most of dry season Longer period of dry  Community perceptions that H H H  As above H H season rainy season start occurs later in May or early June  Projections indicate that monsoon will start more often in May and June Increased P/PET  More evapotranspiration in H VL M  Little impact upon shrimp populations VH L balance in April the dry season compared to 51 precipitation especially increasing in April Change and shift in events Strong winds . More strong winds in April H52 M53 H  Maybe some mortality of shrimps in B. Tonle Chhmar VH M and May after strong winds, though this may not be noticed . Poor water quality in B. Tonle when many larger fish are dying Chhmar Storm events  Increased frequency and L54 VL L  Storms are unlikely to have any impact upon shrimp VH L intensity of rainfall 55 populations  Increased frequency of 80 mm events in one day from 7 per year to 11 per year

49 Shrimps are sensitive to drought conditions, retreating to open water and shallow ponds. They can survive in these ponds, if they do not dry out 50 Drying out of rice fields and ponds is part of natural cycle to which shrimps are adapted. Populations will recover quickly at the start of the wet season 51 Living in the water, shrimps are not affected by the balance of precipitation and evapotranspiration, or only in so far as covered under drought 52 Shrimps living in B. Tonle Chhmar may be exposed to the poor water quality conditions after strong winds when the water levels are low 53 Shrimps are relatively tolerant of low dissolved oxygen in water, especially if this is temporary 54 Unlike with strong winds, storms coming later in the wet season will have less of an effect upon water quality because water levels are higher 55 Rainstorms unlikely to change conditions to which shrimps are sensitive

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System – as for Boeung Chhmar from Beung Kiat Nong wetland assessment

FRESHWATER TURTLES – MALAYEMYS SUBTRIJUGA AND HIEREMYS ANNANDALII

Threat Interpretation of threat Impact Summary

Adaptive capacity Adaptive Vulnerability Exposure Sensitivity Level Impact refer to written description of how the Written explanation of what the impact is, and why table Change and shift in regular climate threat relates to the asset refer to table it was scored (high, med, low) Increase of temperature especially  Increase in temperature of H VH56 VH  Increased temperatures can affect the sex ratio L5859 VH 57 at end of dry season up to 3 deg C increases of the hatchlings - Males tend to be produced evapotranspiration and between the temperatures of 28 – 30oC. Above decreases availability of (and below) these temperature range, mostly water in the wetland in the females will be produced – this results in dry season skewed sex ratio in populations  During dry season mean  Hatchlings coming from eggs closer the surface maximum temperatures (i.e. exposed to higher temperatures) have been rise observed to swim slower and nearer the water  Jan from 31oC to 32.5 oC surface  Feb from 33 oC to 35.1 oC  March from 34.5 oC to 36 oC  April from 34.5 oC to 37.6 oC

56 Nesting for both species starts in dry season – for M. subtrijuga, starts in March/April, and for H. annandalii starts in December Jan and incubation lasts until beginning of wet season, June/July 57 Eggs are deposited in excavated holes in the banks which are then covered back again 58 Only relatively few (4 – 6) eggs are laid at one time 59 Depth of nests can influence incubation temperature, but not clear if female chooses depth depending upon environmental conditions

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Irregular distribution of rainfall in  In January, Feb, March H H H  Permanently inundated areas will become M H dry season, including drought and April, there is less smaller in extent and permanent pools will rainfall (-6%) become shallower.  Increased  Both of these factors will make the turtles easier evapotranspiration to capture  Rainfall in late dry season increases by about 11% in May Increase in rainfall in wet season  10% increase overall in H L M  Rapid wetting and inundation of the wetland H M wet season from May to from the start of the wet season, will increase October the habitat for the turtles  Collection of turtles will be more difficult in wet season because of access, deeper water Change and shift in events

Increased frequency and . One more heavy rainfall M VL L  Storms should have little impact upon turtles, H L intensity of storms event per year which can hide under water. . Intensity of heaviest storm  Flashflows down the small streams may increases from 120 to increase turbidity, but this is unlikely to affect 144mm the turtles Increased risk of Flooding  In August the maximum L VL L  Floods will expand the habitat available to VH L monthly rainfall likely to turtles temporarily, with increase in availability increase from 640 to 680 of food mm in the month  Wet season volume of water will generally be higher and with a high rainfall year the risk of flood will increase  Historically flood occurs may be 1 in 10 years, may be increased frequency slightly

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Annex 3: CAM matrices of Fish species from Mekong ARCC Fisheries study

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INTERNATIONAL UNION FOR CONSERVATION OF NATURE IUCN Asia Regional Office 63 Soi Prompong Sukhumvit 39 Wattana - 10110, Bangkok, Thailand Tel: +66 2 662 4029 www.iucn.org/mekong_water_dialogues

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