Threatening Tonle Sap: Challenges for Southeast ’s largest Freshwater

Claudia Kuenzer

Abstract: The Tonle Sap ecosystem in is ’s largest freshwater lake; strongly impacted by the pulse. The lake is home to exceptional , and rural communities living in free floating villages on the lake and on its shores. The fragile niche ecosystems as well as the rural livelihoods of Tonle Sap are un- der severe threat. Overfishing, illegal wood harvesting, further resource exploitation, and water quality deterioration Source: Michael Waibel 2009 all impact the stability of the socio-ecological system of Tonle Sap. At the same time, expected flood pulse changes due to regulatory measures in the context of hydropower development upstream on the Mekong are a severe threat for Tonle Sap’s ecosystem stability. The area needs to shift into the focus of attention of national and international re- searchers, stakeholders, and decision makers, to find suitable pathways for a future sustainable development of this unique and pristine region.

Key words: Tonle Sap Lake, flood pulse ecosystem, floating villages, rural livelihoods, fisheries

[Submitted as field note: 16 March 2013, Acceptance of the revised manuscript: 31 May 2013]

Introduction to Tonle Sap Lake’s Socio-Ecological System: Tonle Sap Lake in Cambodia is the largest freshwater lake in Southeast Asia. The permanent water body of the Tonle Sap exceeds 2.500 km² in the dry season, and this area more than quadruples to 12.000 km² in the rainy season (August to November). In late June the monsoon waters of the Me- arriving from the North pour into Tonle Sap River, which then reverses its flow direction towards the North and feeds the lake from its southern tip. During this time the lake’s surface expands four- to fivefold and the water volume multiplies up to 50 times, with water depths increasing from one to over 12 meters (Osmose, 2013).

The Tonle Sap is unique in many ways. water level fluctuations – it is the - lar the lake. Most of them live from the Not only the hydrologic regime with its gest seasonally flooded fresh-water rich fisheries: as fishermen, fish traders, vast fluctuations is exceptional in the swamp in Southeast Asia. Shrubs and fish processing experts, or maintaining world. The lake is one of the world’s trees withstand week-long flooding – a services (floating gas stations, schools, top fresh-water fisheries, as well as one unique habitat of unique floristic com- churches, police stations etc.). Some of the world’s largest habitats for sna- position consisting of gallery forest, villages are fully floating villages -per kes, and hosts the largest colonies of short-tree shrub lands, and herbaceous fectly adapted to the rise and fall of endangered water birds in Southeast aquatic vegetation. Most plants shed water levels. The location of those vil- Asia, among them 15 endangered spe- their leaves during submersion in the lages may shift for several tenths of ki- cies such as grey-headed fish eagles, wet season. Leafs then sprout on the lometres between the dry and the wet spot billed Pelicans, black-headed Ibi- trees again from top to bottom (an un- season. Mixed villages contain fully ses, and Adjutants. Mammals include common oddity) after the flood waters floating homes as well as stilt homes macaque monkeys, otters, fishing cats, recede (Osmose 2013). built on 8-10 meter high stilts. Villagers flying foxes and bats, civets, lorises, as About 100,000 people, of which have adapted their life perfectly to the well as domestic animals living close to most are Khmer, live in the over 150 water environment. Children are pi- men. At the same time – due to high floating villages scattered alongside cked up by “school-boats” to visit their Source of all other pictures: Claudia Kuenzer 2013

Pacific Geographies #40 • July/August 2013 29 floating schools, domestic animals such is a shift in catch characteristics (dimi- These threats are further aggrava- as pigs are kept in floating cages, peo- nishing size and quality), from medium ted by upstream developments in the ple catch the daily dinner right in front size and large fish towards an increa- Mekong Basin. Hydropower develop- of their floating house, and plants such sing amount of very small fish, which ments along the main stem and its tri- as invasive water hyacinth or floating do not have a high market value (Ku- butaries cause transboundary effects coconuts etc. are used to weave mats, enzer et al. 2012). Overfishing occurs within the whole Basin (Kuenzer et baskets, or carve bowls. The floating due to the local fishery laws, which dis- al., 2012, Zhao et al. 2008). On the communities of Tonle Sap Lake are tributes part of the lake into different one hand, the provision of hydropo- outstanding in their adaptation to their so called ‘lots’, in which lot operators wer increases economic activity and natural environment. Many of them fish as much as possible. Even though meets the rising energy demand of are located within the “Tonle Sap Bios- overfishing and coastal forest destruc- Mekong riparian countries. On the phere Reserve”, which was established tion is prohibited, the limitations are other hand, the negative impacts of in 2001 by the Cambodian govern- not specified (what IS overfishing), dam construction, mainly altered wa- ment, after UNESCO had declared and law enforcement does not take ter flow and reduced sediment load, Tonle Sap an ecologic hot spot. place. In addition, migratory fisher- confirm downstream country’s fears men (e.g. from northern Thailand) as (Kuenzer et al., 2012). As the Tonle Major challenges well as Cambodian rice farmers, which Sap is connected with the Mekong via Some authors claim the Tonle Sap fish only during the rainy season, come the 100km long Tonle Sap River, the and the Mekong floodplains to be the into the area to fish. This overfishing impact will be directly felt (Lamberts most productive freshwater ecosys- as well as illegal wood harvesting has a 2008). Only slightest changes in the tems in the world (Kummu et al. 2010), direct impact on livelihoods and in the flood pulse characteristics such as the depicting the fish yield in the Tonle mid-term will aggravate poverty. At timing and duration of the flood, the Sap (139-230 kg/ha/yr) to be 700-850 the same time, alternatives for income rate of rise and fall of the flood water per cent higher than in the floodplains generation are rare: local fishermen as well as the height of dry and wet of e.g. the Amazon or the Brahmapu- need to overfish to survive as allo- season water level may alter the com- tra (van Zalinge 2002). Migratory fish wed catch amounts would simply not plex ecologic niches and habitats and species (so called white fish) and resi- be enough to supply an income to the the associated processes that deter- dential fish of the lake itself (so called average rural household of seven peo- mine the Tonle Sap’s ecosystem pro- black fish) are differentiated. However, ple (5 children average). The decrease ductivity (Valbo-Joergensen et al. 2009, even though Baran and Myschwoda in fish has – in many areas – led to a Welcomme and Halls 2004, Lamberts (2008) report that fish catches in the drastic decline in migratory birds and 2008). Lamberts (2008) investigated Tonle Sap and Lower Mekong Basin disturbances in the food chain. On top the consequences of Mekong river are (weight wise) greater now than in of this, water pollution due to socio- flow alterations for the Tonle Sap eco- past decades (attributed to modern economic development around the system and compiled an impressive ta- and partially illegal catch methods, lake threatens local people’s drinking ble of major flood pulse characteristics such as the use of explosives, poison, water supply and lead to the explo- and their susceptibility to being affec- and electrofishing, Valbo-Joergensen sive development of harmful invasive ted by anthropogenic flow alterations et al. 2009), they also find that there plant species, such as water hyacinth. in the Mekong River. For the lake, the timing of the flood is a crucial factor to allow the synchronisation between physiological readiness (for migra- tion, spawning etc.) of the fish and the flood phase. Nesting species’ repro- ductive cycle, for example, may be dis- rupted if water levels rise too fast, and eggs can become emerged if flood wa- ter falls too fast. According to a Cu- mulative Impact Assessment report, which was initiated by the World Bank and the Asian Development Bank and which aimed at examining the conse- quences of hydropower induced wa- ter level changes, dry season water le- vels are expected to rise up to 70 cm at Chaktomuk junction of the Tonle Sap and the Mekong River (Miyazawa et al. 2008). Such drastic changes would se- verely change the local ecosystem.

Conclusion and future needs Summarizing, current threats to the Tonle Sap ecosystem are: Rural livelihood of a coal fisher’s family

30 Pacific Geographies #40 • July/August 2013 Floating stores and storage supplies

• regulatory measures (hydropower, ships within this unique and pristine Kuenzer, C. et al. (2012) Understanding the Im- but also water diversion projects ecosystem is needed. It is crucial that pacts of Hydropower Developments in the context and increasing irrigation) at the up- the rural population of the floating vil- of Upstream-Downstream Relations in the Mekong per reaches of the Mekong and its lages of Tonle Sap can maintain their River Basin. Sustainability Science, Springer, DOI tributaries, directly impacting the safe livelihoods in the future. Further- 10.1007/s11625-012-0195-z. flood pulse and therefore sensitive more, incentive programmes for local Kummu, M., et al. (2010) Basin-wide sediment niche-ecosystems, communities to engage more in the trapping efficiency of emerging reservoirs along the • the loss of flooded forest due to protection of their own environmen- Mekong. Geomorphology 119 (2010): pp 181-197. wood consumption and clear cut- tal resources are urgently needed to Lamberts, D. (2008) Little impact, much damage: ting, leading to changes in the eco- stress the value of biodiversity. Incen- the consequences of Mekong River flow alterations for system (decreasing spawning and tives and the development of new in- the Tonle Sap ecosystem. In: Kummu, M. et al. (eds.) resting grounds for aquatic animals, come sources, such as well-controlled Modern Myths of the Mekong. A critical review of decreased erosion and lake floor and limited eco-tourism can also help water and development concepts, principles and po- protection etc.), to overcome the poverty of the rural licies. Water & Development Publications, Helsinki • overfishing spurred by destructive people living near and on Tonle Sap. University of Technology, pp 3-18. and illegal fishing techniques (lea- At local and national level in Cambo- Miyazawa, N., Sunada, K., and Sokhem, P. ding in the long run to alternative dia most important is an improved law (2008) Bank erosion in the Mekong River Basin: Is requests for protein, and thus lan- enforcement to mitigate activities of bank erosion in my town caused by the activities of duse change in the Mekong Basin), overfishing and resource destruction. my neighbours? In: Kummu, M. et al. (eds.) Modern • water pollution through nearby ci- At regional, international level, the Myths of the Mekong. A critical review of water and ties, villages, and the use of agro- ecosystem of Tonle Sap deserves an development concepts, principles and policies. Water chemicals (impacting biodiversity even greater attention within the trans- & Development Publications, Helsinki University of in and around the , as well boundary Mekong related dialogue of Technology, pp 19-26. as food quality and finally human organisations and initiatives such as Osmose (2013): The waterway: Between Battam- health), the , MRC, bang and – Introduction to the Tonle Sap • the spread of invasive water plant the Initi- great lake’s ecosystem. 31pp. species (hindering transport and ative, GMS, and with further players Van Zalinge, N. (2002) Update on the status of leading to further water quality de- such as governmental research agen- the Cambodian inland capture fisheries sector with terioration), cies, non-governmental organisations, special reference to the Tonle Sap Great Lake. Catch • a lack of income alternatives for international research and develop- and Culture 8 (2): 1-5. the local population and the need ment projects, as well as development Valbo-Joergensen, J. et. al. (2009) Fish Diversity for extensive resource exploitation aid implementation agencies. in the Mekong River Basin. In: Campbell, I.C., (ed.): in the absence of law enforcement. The Mekong – Biophysical Environment of an Inter- References national River Basin, Elsevier, New York, pp 161- Although ecotourism is on-going Baran, E. and Myschwoda, C. (2008) Have fish 196. at small scale, and although first non- catches been declining in the Mekong River Basin? Welcomme, R.L., and Halls, A.S. (2004) De- governmental organizations have set In: Kummu, M. et al. (eds) Modern Myths of the pendence of tropical river fisheries on flow. In: Wel- foot into the area to support sustaina- Mekong. A critical review of water and development comme, R.L. and Petr, T. (eds) Proceedings of the se- ble resource management, extended concepts, principles and policies. Water & Develop- cond international symposium on the management of research, capacity-building, and aware- ment Publications, Helsinki University of Technology, large for fisheries, Volume II, RAP Publication ness-raising on the complex relation- pp 55-64. 2004/16, FAO, Bangkok, pp 267-283.

Dr. Claudia Kuenzer [[email protected]] received her PhD from Vienna University of Technology in 2005 and is head of the group ‘Land Surface Dynamics’ at the Earth Observation Centre, EOC, of the German Aerospace Centre, DLR, Oberpfaffenhofen, 82234 Wessling, Germany.

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