ASSESSMENT OF THE CARBON SEQUESTRATION POTENTIAL OF MANGROVES IN CITY Terminal Report

BUILDING LOW EMISSION ALTERNATIVES TO DEVELOP ECONOMIC RESILIENCE AND SUSTAINABILITY PROJECT (B-LEADERS)

January 2017

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TABLE OF CONTENTS

TABLE OF CONTENTS ···················································································· I

LIST OF TABLES ························································································· III

LIST OF FIGURES ······················································································· III

I. EXECUTIVE SUMMARY ····································································· VIV

II. INTRODUCTION ·················································································· 1

1.1. Objectives ...... 2 1.2. Scope and Limitations of the Study ...... 2 III. METHODOLOGY ················································································· 3

2.1. Study Site ...... 3 2.2. Sampling Requirement ...... 4 2.3. Carbon Stock Accounting ...... 5 2.4. Total Carbon Stock or The Total Ecosystem Carbon Pool ...... 6 2.5. Forest Structure and Composition ...... 6 IV. RESULTS AND DISCUSSION ································································· 7

3.1 Species Composition and Stand Structure...... 7

3.1.1 Species Composition ...... 7

3.1.2 Stand Structure...... 7

3.2 Floristic Diversity ...... 8

3.2.1 Site 1 (Sta. Rita and San Lorenzo) ...... 9

3.2.2 Site 2 (Cuta, Malitam and Wawa) ...... 10

3.2.3 Site 3 (Barangay Tabangao) ...... 11

3.3 Land Cover / Land Use Change ...... 17 3.4 Biomass and Carbon Stock ...... 18 3.5 Sediment Carbon Stock ...... 23

3.6 Potential Economic Value of carbon stocks ...... 26 3.7 Potential Mangrove Rehabilitation Sites ...... 27 V. IMPLICATIONS OF THE STUDY ··························································· 28

VI. CONCLUSION AND RECOMMENDATIONS ··········································· 31

VII. ANNEXES ·························································································· 32

ANNEX 1. Sediment Sampling Activities In Various Mangrove Sites Of ...... 33 ANNEX 2. Partial List Of Mangrove Species Identified For Site 2: Barangay Cuta, Malitam And Wawa With Their Iucn Conservation Status, Economic Importance And Threats ...... 34 Annex 3. Partial List Of Mangrove Species Of Barangay Tabangao With Their Iecn Conservtation Status, Economic Importance And Threats ...... 35 ANNEX 4. Research Team ...... 35 ANNEX 5. Literature Cited ...... 37

LIST OF TABLES

Table 1. Sampling requirement based on identified mangrove sites ...... 4

Table 2. Categories of diversity values ...... 6

Table 3.List of species documented in the area with corresponding frequency ...... 7

Table 4. Five species with the highest diameter ...... 8

Table 5. Diameter range with corresponding number of individuals ...... 8

Table 6. List of all species in Barangay Sta. Rita with their respective importance values ...... 12

Table 7. Frequency and Diversity Index of Mangrove Stand of Barangay Sta. Rita ...... 13

Table 8. List of all species in Site 2: Barangays Cuta, Malitam and Wawa with their respective importance values ...... 14

Table 9. Frequency and Diversity Index of Mangrove Stand of Barangay Cuta ...... 14

Table 10. Frequency and Diversity Index of Mangrove Stand of Barangay Malitam ...... 15

Table 11. Frequency and Diversity Index of Mangrove Stand of Barangay Wawa ...... 15

Table 12. List of all species in Site 3: Barangay Tabangao with their respective importance values ...... 15

Table 13. Frequency and Diversity Index of Mangrove Stand of Barangay Tabangao ...... 16

Table 14. Land use and land cover area distribution of Batangas City, across three periods (1997, 2006 and 2016) ...... 17

Table 15. Carbon stock capacity of Site 1 (Sta. Rita and San Lorenzo) ...... 18

Table 16. Carbon stock capacity of Site 2 (Cuta, Malitam and Wawa)...... 20

Table 17. Carbon stock capacity of Site 3 (Tabangao) ...... 21

Table 18. Soil carbon stock of mangrove stands in different barangays in Batangas City ...... 24

Table 19. Sediment carbon stock of mangrove stands in Site 1(Sta. Rita and San Lorenzo) ...... 24

Table 20. Soil carbon stock of mangrove stands in Barangays Malitam, Cuta and Wawa ...... 25

Table 21. Soil carbon stock of mangrove stands in Barangay Tabangao ...... 25

LIST OF FIGURES

Figure 1. Location Map of Batangas City ...... 3

Figure 2. Location Map of the three mangrove sites (Site 1: San Lorenzo and Sta. Rita; Site 2: Malitam, Wawa & Cuta; and Site 3: Tabangao) ...... 4

Figure 3. Land use and land cover maps of Batangas City, Philippines based on three observation periods (1997, 2006 and 2016) ...... 18

Figure 4. Total carbon stock distribution of three mangrove sites in Batangas City, Philippines ...... 22

Figure 5. Total carbon dioxide (ktCO2) storage capacity of Batangas City mangrove forest ...... 23

Figure 6. Potential mangrove rehabilitation sites in Batangas (Source: Google Earth ver. 7.1.2.2019) . 27

I. EXECUTIVE SUMMARY

Over the past half century, 50% of the world’s mangrove forest has been exploited despite being a valuable economic resource. Mangrove areas have been converted for urban development, agriculture, shrimp and fish farming, and for salt and rice production to meet the demand of the increasing population. The loss of mangrove cover remarkably decreases its ability to sequester atmospheric carbon. A great proportion of carbon stock is imbedded in the organic-rich sediment which unfortunately is susceptible to emission if mangrove vegetation are disturbed. Quantifying carbon stocks will provide ecological and economic perspectives of mangrove ecosystem values.

In the Philippines, Batangas City is one of the key marine biodiversity sites along the Verde Island Passage. It has a 26.48 hectares of mangrove cover but its decline is inevitable as it is considered a major urban and industrial center. Thus, Batangas City is a good case for carbon accounting and valuation. This will help rationalize the need for the rehabilitation and the continuous protection of the city’s mangrove forest. With this, a collaborative study between the City of Batangas,and USAID with the assistance of the University of the Philippines Los Baños, was conducted to assess the baseline and potential carbon stocks of mangroves in the city and estimate their prospective economic value. This was done through carbon stock accounting and valuation. This method refers to the assessment of baseline and projected biomass and carbon stocks in two carbon pools, namely: aboveground (vegetation); and belowground (sediment). This study focused on relatively large patches of mangroves found in the six coastal barangays. Non-destructive sampling was done by using allometric or biomass estimation models for carbon stocks computation. Forest structure and composition was also recorded to know the different mangrove species present and its abundance and diversity in the area.

Results showed that there were five hundred ninety-six (596) individuals that belong to 9 mangrove species, 4 families, and 6 genera in the 23 plots established in the three sites. The most dominant species is Bungalon/Pipisik (Avicennia marina) with 292 individuals while the least dominant species is Malatangal (Ceriops zippeliana) with just 1 individual. In terms of stand structure, 87% of the mangrove trees have small diameter (0-15 cm), 12% have medium diameter (15.1-30 cm) and only 3 individuals have large diameter (30.1-above). This showed that Batangas mangrove is relatively young since majority of each tree species belong to the small diameter class. Among the three sites, assessment has shown that Barangay Sta. Rita is an asset as it has a diverse community of mangroves with 10 species that belong to six families. This site can be considered a potential seed bank. On the other hand, the urban barangays of Cuta, Malitam, and Wawa has retained a mangrove patch of at most 5 species belonging to 3 families. This is the same with Barangay Tabangao.

From the three sites surveyed, results showed that the mangrove forest of Batangas City has a total carbon storage capacity of 29.92 ktCO2. Among the sites, Site 1 (Sta Rita and San Lorenzo) sequestered a total carbon dioxide of about 16.59 ktCO2, the highest among the three sites. This comprised 55% of the city’s overall mangrove carbon stock. This is followed by Site 3 (Tabangao) with 10.10 ktCO2 wherein carbon was found higher in sediment with 125.6 tC ha-1 than in vegetation with 95.4 tC ha-1. Site 2 has a carbon stock of only 3.22 ktCO2. In contrast with the two other sites, vegetation layer here contributed more carbon stocks with 123.5 tC ha-1, while 80.5 tC ha-1 was

found in the sediments. Based on this, the carbon stock of the three sites is worth USD 98,149. Potential sites for future mangrove rehabilitation was roughly estimated to 504 ha. In the three sites (six barangays), 90.8 ha can be potentially rehabilitated while 413.3 ha can be potentially rehabilitated from other sites along the Batangas coast. Using the mean carbon stock estimates obtained from the three sites, these areas could have an overall potential capacity of 177.1 ktCO2 (for vegetation) and 372.1 ktCO2 (for sediment). The calculated economic value is worth USD 1.81 million.

The evaluation of the carbon stocks in the three mangrove sites in Batangas City conveys several important implications in support of mangrove conservation and rehabilitation agenda of the country.

Low species diversity. Floristic diversity is generally low due to different natural, environmental, and anthropogenic factors. Natural factors include the mangroves ability to naturally grow and predominate certain habitats while environmental factors include tidal changes, exposure to sunlight, and wind. On the other hand, anthropogenic factors include illegal tree cutting, conversion of mangroves to settlement areas, and waste dumping that lead to deforestation.

Rich sediment carbon stocks. Most of the nearby upstream towns of Batangas City are primarily used as an agricultural land resulting to very high sedimentation and organic matter deposition. The mangrove filters and captures these organic materials to avoid reaching and harming the seagrass and coral beds.

Economic potential of carbon stocks. The mangrove carbon stock has a huge economic value that an incentive-based program such as carbon offset projects (e.g. REDD Plus) can be pursued in the near future. With this possible opportunity, programs should be focused on coastal protection and rehabilitation.

Need for sound rehabilitation. Increasing floristic diversity and reviving important ecosystem services such as carbon sequestration should be the aim in pursuing coastal rehabilitation. This should be in partnership with the local government, local communities and private industries for better success in rehabilitation.

Enforcement of environmental laws. Crafting local policies, enforcement of existing ones, and institutionalization of individuals/groups from the local government and non-government sectors that will monitor compliance should be done to address the problems of mangrove deforestation and degradation.

Strengthening partnership through co-management approach. Pursuing co-management of mangroves will aid in raising local commitment on forest conservation and rehabilitation. A tool like Corporate Ecosystem Services Review (CESR) can be introduced to guide industries on how to assess environmental impacts based on their level of dependence on a particular natural resources and how to address negative impacts on the environment.

Opportunities towards green growth. The computed value of carbon stock indicates that the mangrove can be used as basis for conservation and rehabilitation efforts of the Batangas City government. The findings can aid on their future investment on programs that promotes sustainable use of mangrove resources and services.

All in all, the computed carbon stock of the three study sites were found to be significantly high suggesting that mangroves are generally good carbon sinks. Focus on the increase of floristic diversity

and carbon storage of each individual mangrove stand would be a good contribution to mitigate global warming and climate change. Moreover, the observed high potential of mangroves for carbon storage translates into high economic value. This could be further improved with sound and effective management interventions stemming from the local government, concerned local communities, and private institutions. These future management initiatives and policy enforcement should paved the way towards the sustainable use of mangroves’ ecosystem services and eventually to the increased harvest of its benefits. Lastly, it is recommended that results of this study should be considered in mainstreaming natural capital accounting and green growth initiatives in policy formulation and decision-making.

II. INTRODUCTION

Mangroves are among the world’s most important ecosystems. They enrich coastal waters, yield commercial forest products, protect coastlines, and support coastal fisheries. They have unique characteristic by being true ecotones of land and ocean. The term mangrove denotes two different concepts according to Lugo and Snedaker (1974) and Alongi (2010). Firstly, it refers to a group of salt-tolerant plants belonging to nine orders, 20 families, 27 genera, and roughly 70 species. These plants can cope with changes in water and sediment salinity by evolving both xeromorphic1 and halophytic2 characteristics. Secondly, it refers to complex plant communities that fringe tropical and subtropical (32° N to 32° S) shores and delimited by major ocean currents and 20 °C isotherm of seawater in winter. Mangrove forests are also well adapted to deal with natural stressors such as high temperature, high salinity, anaerobic sediments, and extreme tides. However, because they live close to their tolerance limits, they are sensitive to other disturbances like those that are brought by human activities (FAO 2007). In many regions, mangrove stands are already in the brink of complete collapse after being favored as sewage disposal sites and aquaculture ponds (Kathiresan and Bingham 2001).

Fifty percent loss in the world’s mangrove forest over the past half century reflects the fact that mangroves are indeed valuable economic resources that are being wasted. According to Costanza et al. (1998), global mangrove forest is worth US$ 180,900,000,000 and their average monetary value is estimated to US$ 10,000 ha-1 yr-1. Albeit such value, they are often unappreciated. The high population pressures in coastal zones had converted mangrove areas for urban development. In order to augment food security and boost national economies, many governments have also encouraged development of agriculture, shrimp and fish farming, and salt and rice production in mangrove areas. These have therefore resulted to massive fragmentation, degradation, and pollution of coastal areas. The Philippines is no exception as its mangrove cover has declined mainly due to conversion to aquaculture ponds. Based on early estimates, mangroves used to cover around 400,000–500,000 ha (Brown and Fischer 1920; Chapman 1976; Primavera 2000). This was trimmed down to 153,577 ha with fairly extensive mangroves left that can be found in Palawan with 41,830 ha (DENR 2005).

Consequently, mangrove cover loss implies a tremendous decrease in the forest biomass which could have been instrumental in sequestering atmospheric carbon. A healthy mangrove stand could store around 300 to 1023 tC ha-1 (Lasco and Pulhin, 2000; Gevana and Pampolina, 2009; Donato et al., 2011). It is therefore crucial to rehabilitate and protect mangrove forests to this critical role of mitigating global warming and its related climate change impacts.

1 Xeromorphic characters are adaptations that enable plants to conserve water. 2 Halophytes are plants that show adaptations for living under high salt conditions, such as plants that live near the sea shore.

For mangrove rehabilitation efforts to be more relevant, information about their carbon sequestration potential are vital. Quantifying carbon stocks will provide ecological and economic perspectives of mangrove ecosystem values. This can be done through carbon stock accounting and valuation. Carbon stock accounting pertains to the assessment of baseline and projected biomass and carbon stocks in two carbon pools, namely: aboveground (vegetation); and belowground (sediment). Carbon stock of mangroves (together with other marine ecosystems) is known as blue carbon. On the other hand, carbon stock valuation pertains to economic valuation of baseline and projected carbon stocks i.e based on prevailing prices in the carbon market (including those in voluntary markets). Such value provides a decision tool for ‘investing in’ rehabilitation and ‘forgoing of’ mangrove cover vis-à-vis other coastal development activities.

Mangrove site in Batangas City, Philippines offers a good case for carbon accounting and valuation being located in a highly urbanized setting. By estimate, it covers about 26.48 ha, concentrated at the mouth of Calumpang River. A number of threats to its survival were identified, namely: 1) conversion to settlement and industrial port; 2) heavy siltation due to intensive agriculture active from the upstream; 3) deterioration of water quality due to household and industry wastes being dumped in Calumpang River; and 4) some tree cuttings for domestic fuel wood need. Given this, accounting and valuing the potential carbon stocks will help rationalize the need for rehabilitation and continues protection, in view also of the countless ecosystem services that will be lost if deforestation and degradation will continue.

1.1. OBJECTIVES

This study aimed to assess the baseline and potential carbon stocks of mangroves in Batangas City and estimate their prospective economic value. Specifically, it endeavored to:

a. assess the species composition and community structure of mangrove stands; b. assess the mangrove cover and land-use changes; c. quantify the aboveground and below-ground biomass and carbon stocks; and d. estimate the potential economic value of carbon stocks e. provide recommendations in pursuing carbon offset project.

1.2. SCOPE AND LIMITATIONS OF THE STUDY

This study covered six (6) mangroves sites in Batangas City particularly focusing on relatively large patches found in each coastal barangays. Non-destructive sampling was done by using allometric or biomass estimation models to compute carbon stocks.

III. METHODOLOGY

2.1. STUDY SITE

Batangas City is one of the key marine biodiversity sites along the Verde Island Passage (Figure 1). Its mangroves cover about 26.48 hectares. The city has cove-like bay situated at the south-eastern portion of the province. It is bounded on the northwest by the municipality of San Pascual; on the north by the municipality of San Jose; on the east by the municipalities of , and Lobo; and on the south by the Batangas Bay. Majority of the land or 39.66% of the total land area of the province is dedicated for ecological development area (forest land, watershed, tourism etc.).

Figure 1. Location Map of Batangas City

The guidelines for sample computation approved by United Nations Framework Convention on Climate Change (UNFCCC) for Clean Development Mechanism (CDM) projects (i.e. AR-AM0001, AM0005, and AM0006) was used to determine the number of sampling plots required (Pearson et al. 2005). An online plot calculator tool 3 developed by Winrock International was used in plot

3 Carbon plot calculator tool used by Winrock International based on AR-AM0001, AM0005 and AM0006 methods (Available at: www.winrock.org/Ecosystems/tools.asp)

calculation (Pearson et al. 2005). Information needed (e.g. mean carbon stock and standard deviation of carbon stock) are based on the report of Gevana et al. (2008) in a nearby mangrove site in San Juan, Batangas Province. To determine the minimum number of sample plots, the following equation was used:

2.2. SAMPLING REQUIREMENT

Eighteen (18) sample plots measuring 10m x 10m are required to determine the total amount of carbon stock of the study site. These plots were randomly located within the following sites (Table 1 and Figure 2). Coordinates of sample plots were obtained. Inside each plot, all living trees with a diameter at breast height (DBH) of 5cm and above will be listed and accounted.

Table 1. Sampling requirement based on identified mangrove sites

Sampling No. of Plots No. of Plots Location Area (hectare) Site No. required Established 1 San Lorenzo and Sta. Rita 9.70 7 8

2 Malitam 0.85 1 2 Wawa 1.10 1 2 Cuta 2.36 1 2 3 Tabangao 12.47 8 9 TOTAL 26.48 18 23

Figure 2. Location Map of the three mangrove sites (Site 1: San Lorenzo and Sta. Rita; Site 2: Malitam, Wawa & Cuta; and Site 3: Tabangao)

2.3. CARBON STOCK ACCOUNTING

Aboveground or total tree biomass (kg) was calculated using allometric or biomass equations as suggested by Komiyama et. al. (2005). All tree biomass for each plot was summed to get the total biomass (expressed in ton ha-1). Biomass was converted to the equivalent amount of carbon (46% on the average), based on the previous studies conducted by Lasco et al. (2001) and Gevana (2014).

2 1.23 Aboveground biomass (Wtop) = 0.247 p (D )

For Rhizophoras, root biomass will be computed using the following formula: 0.899 2 1.11 Root biomass (WR) = 0.196 p (D )

Where: p is the wood density of the species D is the diameter at breast height (cm) H is height (m) Sediment carbon assessment has two components: soil carbon content analysis; and soil carbon stock measurement. Carbon content analysis involved the collection of about 200g of sediment samples from the organic matter (OM) layer of undisturbed portion of the plot. Organic matter layer was determined by digging the sediment using a tamper bar during low tide event. Height or thickness of OM was measured using a meter tape, as this will represent the carbon layer of the sediment. Samples were sent to soil laboratory UP Los Baños for carbon content analysis.

For the sediment carbon stock component, bulk density was determined by choosing an undisturbed spot inside plot, carefully driving core samplers into the organic layer of the sediment. Core samples at varying depths were collected from each plot and later subject for oven drying (at 105oC). To compute the sediment carbon stock, the following equations were used: Bulk Density (g cm -3) = Dry weight of core (g) / volume of cylinder (cm3) Sediment mass (t ha-1) = bulk density * 10000m2 * OM depth (m)

Sediment carbon stock (tC ha-1) = sediment mass * % carbon content

2.4. TOTAL CARBON STOCK OR THE TOTAL ECOSYSTEM CARBON POOL

The total carbon stock or pool was estimated by adding all of the component pools. First, each component pool is averaged across all plots.

-1 Total carbon stock (tC ha ) = Carbon Stockaboveground + Carbon Stockbelowground

Litter at the forest floor was not included in the assessment recognizing their absence during sampling time. This condition is common since tidal changes displace and flush out canopy debris from mangrove areas to the sea (Alongi 2010).

2.5. FOREST STRUCTURE AND COMPOSITION

Species composition and biometric measurements (diameter, height and stand density) was determined for each sample plot. Diversity index (Table 2) was also measured to further describe the vegetation. Understory vegetation was documented to have a full picture of the general characteristics of the mangrove stand. Dominant species were determined by computing the Importance Value (IV) of each species. This ecological parameter was used to rank the species according to the frequency of its occurrence in the entire sampling area (Relative Frequency), the total number of individuals per species (Relative Density) and how dominant the species is relative to the forested area (Relative Cover).

Table 2. Categories of diversity values

Relative values H’ Values Very high > 3.5000 High 3.0000 – 3.4999 Moderate 2.5000 – 2.9999 Low 2.0000 – 2.4999 Very low < 1.9999

IV. RESULTS AND DISCUSSION

3.1 SPECIES COMPOSITION AND STAND STRUCTURE

3.1.1 Species Composition

Five hundred ninety-six individuals belonging to a total of 9 true mangrove species, 4 families and 6 genera were documented in the twenty-three (23) plots established. Dominant family is the Rhizophoraceae with four representative species (Table 3). The most dominant species in terms of frequency of occurrence are Bungalon/Pipisik (Avicennia marina) with a total of 292 individuals followed by Bakauan Lalake (Rhizophora apiculata) with 138 individuals. The species with the least occurrence is the Malatangal (Ceriops zippeliana) with just a single individual documented in Plot 4 in Barangay Sta. Rita.

In terms of species composition per barangay, Barangay Sta. Rita has the highest species composition with seven (7) species, followed by Tabangao with five (5) species. This is understandable since majority of the sampling points are concentrated on these barangays (8 plots in Barangay Sta. Rita and 9 plots in Barangay Tabangao).

Table 3.List of species documented in the area with corresponding frequency

Common Name Scientific Name Family Name Frequency Bungalon/Pipisik Avicennia marina (Forsk.) Vierh. Acanthaceae 292 Api-api Avicennia officinalis L. Acanthaceae 15 Langarai Bruguiera parviflora Wight and ArnoRhizophoraceae ex Griffith 6 Malatangal Ceriops zippeliana Sheue et al. Rhizophoraceae 1 Buta-buta Excoecaria agallocha L. Euphorbiaceae 10 Bakawang Lalake Rhizophora apiculata Bl. Rhizophoraceae 138 Bakawang Babae Rhizophora mucronata Poir. Rhizophoraceae 70 Pagatpat Sonneratia alba J. Smith Lythraceae 30 Pedada Sonneratia caseolaris (L.) Engler Lythraceae 34

3.1.2 Stand Structure

Among the five Barangays, Barangay Cuta holds the five individual species with the highest diameter. Pedada (Sonneratia caseolaris) has the highest diameter recorded from the survey with 35.8 cm followed by Bungalon (Avicennia marina) with 33.6 cm (Table 4). It can be deduced from this observation that mangrove forest in Barangay Cuta is the oldest mangrove forest among the sampled five Barangays.

Table 4. Five species with the highest diameter

Diameter Common Name Scientific Name Family Name (cm) Pedada Sonneratia caseolaris (L) Engler Lythraceae 35.8 Bungalon Avicennia marina (Forsk.) Vierh. Acanthaceae 33.6 Bungalon Avicennia marina (Forsk.) Vierh. Acanthaceae 31.2 Bungalon Avicennia marina (Forsk.) Vierh. Acanthaceae 29.4 Bungalon Avicennia marina (Forsk.) Vierh. Acanthaceae 27.7

Of the total five hundred ninety-six (596) individuals recorded, more than 87% (523/596) are small diameter trees, while about 12% (70/596) belong to medium size diameter class and only three individuals are considered large size trees (Table 5). This forest structure is common among mangroves because only few mangroves species can reach a diameter of more than 30 cm. Therefore, it can be considered that Batangas mangrove is relatively young since majority of each tree species belong to small diameter class.

Table 5. Diameter range with corresponding number of individuals

Diameter Class No. of individuals Small (0-15 cm) 523 Medium (15.1-30 cm) 70 Large (30.1 above) 3

3.2 FLORISTIC DIVERSITY

Mangrove diversity provides significant environmental goods and services that in effect play a critical role in supporting human well-being through climate regulation, food security and poverty reduction (UNEP, 2014). Despite its complex role in the human-ecological system, mangroves forest are primarily threatened by the destruction and removal of mangrove areas for conversion to aquaculture, agriculture, overexploitation, urban and coastal development (Polidoro et al., 2010). Although it has been well documented that the primary reason for mangrove forest reduction in the Philippines is the conversion of mangal areas for aquaculture purposes, urbanization and related activities such as reclamation, settlements and industries has also contributed to the denudation of mangrove communities (Primavera, 2000). Case on point for many urban centers in the Philippines, Metro and has almost absent mangal communities. Thus, with Batangas City as a major urban commercial and industrial center, the fragmentation and eventual loss of mangrove forests is inevitable.

3.2.1 Site 1 (Sta. Rita and San Lorenzo)

The results of the assessment clearly indicates that the mangrove area found in Barangay Sta. Rita is an asset for Batangas City considering that it is a community of ten species belonging to six families. In fact, it is home to four unique species, Excoercaria agallocha, Ceriops zippeliana, Bruguiera gymnorrhiza and Aegiceras corniculatum as compared to other barangays. Although all species are common and of least concern due to their low extinction rates of 20-24%, this community should be considered a potential seed bank. They can be potential sources of propagules for reforestation efforts considering that some of the species present have low seed viability particularly Sonneratia sp. (Polidoro et al, 2010).

Based on the computed IV (Table 6), the three most important species in Barangay Sta. Rita are A. marina (175.085), S. alba (41.830), and R. apiculata (29.357). A. marina alone accounts to about 58% (175.085/300) of the total importance value for all trees, indicating the prevalence of these two species. This high importance value of the A. marina across zones is expected since it appeared in all plots which is normal for it can thrive in all levels of the intertidal flat (Polidoro et al., 2010). It is clearly manifested that there is the landward zone where it is identified by presence of E. agallocha, the intermediate zone where it is identified by the presence of C. zippeliana and several B. gymnorrhiza and Rhizopora saplings while the fringing zone where there is an abundance of Avicennia sp., Sonneratia.sp. and A. corniculatum saplings (Polidoro et al., 2010). The presence of several saplings with no adult individual observed indicates that recruitment is still high in the area.

The mangal community in Barangay Sta. Rita is within the property of a gas-fired power plant. The privatization of mangrove areas is a widespread mechanism in the Philippines. This happens when local residents and/ or outsiders stake claim on mangrove areas by paying real estate tax. Then when the government fails to properly monitor the land classification, mangrove areas are eventually privatized through de facto (real estate tax) or legal means (Primavera, 2000). Although, privatization does not assure a great level of stewardship over a resource (Gilmour et al., 2012), the situation in Barangay Sta. Rita prove otherwise. In fact, among the five barangays in Batangas City with mangrove patches, it is the mangrove stand at Barangay Sta. Rita that has the highest diversity (Table 5). The diversity index of barangay Sta. Rita is in fact higher as compared to rural areas such that of Bahile (Abino et al., 2014) and Tiniguiban Cove (Becira, 2006), Puerto Princessa, Palawan. Nevertheless, it is lower as compared to other high diversity-mangrove areas in Bais, Negros Occidental (King et al., n.d.) and Dinagat Island (Cañizares and Seronay, 2016). Having these values as compared to other parts of the country tells a story that this mangrove stand has been protected although it is possible that concerted efforts may increase diversity further. Success stories on privatization and conservation has well been documented in Vietnam where the privatization of formerly state- owned lands have led to afforestation since the households’ economic incentive from afforestation is higher as compared to when they have to compete in the use of a resource (Nguyen et al., 2010). In fact many economists see privatization as an alternative to government control over resources for more efficient long term resource use (Gilmour et al., 2012). However, other studies show that privatization may in fact accelerate development and degradation of natural resources (Medellin et al., 2011). This irony clearly implies that the conservation status and sustainability of this mangrove patch in Barangay and Sta. Rita lies in the degree of stewardship and type of decisions this private entity partakes.

3.2.2 Site 2 (Cuta, Malitam and Wawa)

Ironically though, urban barangays Cuta, Malitam, and Wawa has retained a mangrove patch of at most five species belonging to three families (Table 8-11). This number is low considering that there are 35 true mangrove species in the Philippines (Long and Giri, 2011). Considering the low species richness, the diversity is expectedly low in all three barangays with almost similar species present except for B. parviflora in Barangay Cuta although each site is dominated by a different species, A. marina, R. mucronata, R. apiculata for Barangay Cuta, Malitam and Wawa respectively. This is indicative of the different biophysical conditions in the area such as tidal inundation, salinity and sediments (Duke et al., 1998). According to the Batangas website, these three barangays have indeed different soil types. They respectively have Taal sandy loam, Ibaan clay loam and hydrosols.

The coexistence of the species identified in the survey conforms to the clusters observed by Sinfuego and Buot (2014) in Ajuy and Pedada Bay, Panay Island. Related to their findings, what is observed in Barangay Cuta is referred to as the Avicennia-Sonneratia Zone whilst those observed in Barangays Malitam and Wawa are referred to as Avicennia-Rhizopora Zone. Since Sinfuego and Buot (2014) based this on the dominant species, it may be said though that Barangay Wawa is more of a Rhizopora Zone, a zone not described in the study of Sinfuego and Buot (2014). This observation is best supported with the computed high importance values (IV) of these species in the sampled areas (Table 8). Based on the computed IV, the three most important species (with the highest IV) are R. apiculata (91.789), A. marina (82.372), and R. mucronata (55.372). R. apiculata and A. marina account to about 58% (174.162/300) of the total importance value for all trees, indicating the over dominance of these species.

Apart from the distinction between barangays, a zonation pattern was also observed within the barangay. As observed in the sampled plots for Barangay Cuta, A. marina dominated the landward zone while S. caseoralis and B. parviflora appeared seaward. Both the A. marina and S. caseoralis thrive in the fringing zone. A. marina can thrive across the high, mid, low and under water in the tidal flat while S. caseoralis and B. parviflora is limited within the low and underwater portions of the tidal flat (Polidoro et al., 2010). As for Barangay Malitam, Rhizopora sp. appeared landward while A. marina and S. caseoralis appeared seaward with appearance of the mangrove associate Nypa fruticans, Such distribution across space coincides with the tidal inundation preferences of the species (Polidoro, 2010). This is also attributed to the ecophysiological requirements of the species where Rhizopora sp. have lesser salt tolerance to Avicennia sp. since the latter have salt glands while the former has none (Naidoo, 2016). Barangay Wawa has almost the same pattern with Barangay Malitam except of the rare frequency of A. marina indicative that the mangrove stand in this barangay has not yet infiltrated the coastal zone. Based on zones occupied, it may be said therefore that functional diversity is higher in Barangay Malitam which is consistent in the highest species diversity values generated among the three barangays.

All species identified are of least concern based on their IUCN status (Polidoro et al., 2010) primarily because they are commonly distributed and fast growing except for B. parviflora which in contrast is a slow grower. Despite being a fast grower and a pioneer species, S. caseoralis has very low seed viability (Polidoro et al., 2010) hence making Barangay Cuta a potential source of seeds knowing that numerous seeds may be needed to ensure successful reforestation in the future. Furthermore, these mangrove patches should be considered as an asset and protected to prevent the further loss of these species globally which is at a rate of 20-21% and to lessen the pressure in the thought that the

Philippines remains to be one of the areas of global concern for mangrove species extinction (Polidoro et al., 2010).

3.2.3 Site 3 (Barangay Tabangao)

The mangrove communities in Barangay Tabangao only consist of five species namely R. mucronata, S. caseoralis, A. marina, S. alba, and R. apiculata belonging to three families were observed (Table 13). Urbanization could also entail the discharge of effluents into rivers and estuaries that could pollute mangrove ecosystems by the adsorption of the pollutants onto particulate material in the rivers (Baudo et al., 1990). Despite urbanization though, A. marina was still able to dominate the area as indicated with its high importance value (Table 12). This species have been considered as a bioindicator and is relatively tolerant to pollutants. A. marina var. australasica is prevalent in many heavy metal polluted locales within south-eastern Australia (Irvine and Birch, 1998). Barangay Tabangao is best described as an Avicennia-Rhizopora-Sonneratia Zone (Sinfuego and Buot, 2014). Rhizopora are typical inhabitants of the intermediate zone as indicated to having the highest importance value in plots 1-2 (Table 12) while Avicennia-Sonneratia are inhabitants of the seaward zone of the intertidal flat as shown to have the highest importance value in plots 3-9 (Polidoro, 2010).

Despite the low extinction rates (20-21%) of the species in the area (Polidoro, 2010) this mangrove patch in Barangay Tabangao could be a valuable resource for human sustainability. In fact, mangrove ecosystems cater to other organisms such us macro invertebrates, fishes and epiphytes (Lugo, 2014), thus the low species diversity of the mangroves of Barangay Tabangao should be taken as a challenge for further conservation efforts. In fact, due to the wide array of ecosystem services mangrove ecosystems provide (Lugo, 2014), it should be conserved and protected against the adverse effects of urbanization.

Table 6. List of all species in Barangay Sta. Rita with their respective importance values

Basal Total Common Name Scientific Name Count Area RDom Density RDen Frequency RFreq IV DBH (cm) (m2)

Bungalon/Pipisik Avicennia marina 106 937.102 68.971 83.920 13.250 56.383 1.000 34.783 175.085

Pagatpat Sonneratia alba 25 266.616 5.583 6.793 3.125 13.298 0.625 21.739 41.830

Bakauan Lalake Rhizophora apiculata 30 221.861 3.866 4.704 3.750 15.957 0.250 8.696 29.357

Api-api Avicennia officinalis 15 191.431 2.878 3.502 1.875 7.979 0.500 17.391 28.872

Buta-buta Excoecaria agallocha 10 102.814 0.830 1.010 1.250 5.319 0.250 8.696 15.025

Pedada Sonneratia caseolaris 1 23.491 0.043 0.053 0.125 0.532 0.125 4.348 4.932

Malatangal Ceriops zippeliana 1 14.006 0.015 0.019 0.125 0.532 0.125 4.348 4.898

Legend: DBH – diameter at breast height; RDom – Relative Dominance; RDen – Relative Density; RFreq – Relative Frequency; and

IV –Importance Value

Table 7. Frequency and Diversity Index of Mangrove Stand of Barangay Sta. Rita

Common Name Scientific Name Family Frequency pi ln pi pi*ln pi

Api-Api Avicennia officinalis L. Acanthaceae 19 0.039749 -3.225171753 -0.128197204

Pipisik Avicenia marina (Forsk.) Vierh Acanthaceae 191 0.399582 -0.917337304 -0.366551099

Buta-Buta Excoercaria agallocha L. Euphorbiaceae 8 0.016736 -4.090169191 -0.068454714

Malatangal Ceriops zippeliana Rhizophoraceae 30 0.062762 -2.768413351 -0.173749792

Pedada Sonneratia caseoralis (L.) Engl. Lythraceae 1 0.002092 -6.169610732 -0.012907135

Busain Bruguiera gymnorrhiza (L.) Lamk. Rhizophoraceae 30 0.062762 -2.768413351 -0.173749792

Saging-saging Aegiceras corniculatum (L.) Blanco Myrsinaceae 20 0.041841 -3.173878459 -0.132798262

Nipa Nypa fruticans Wurmb. Palmae 8 0.016736 -4.090169191 -0.068454714

Pagatpat Sonneratia alba L. Smith Lythraceae 66 0.138075 -1.97995599 -0.273383045

Bakawang lalake Rhizophora mucronata Lamk. Rhizophoraceae 105 0.219665 -1.515650382 -0.332935753

478 -1.73118151

Diversity Index 1.73118151

Table 8. List of all species in Site 2: Barangays Cuta, Malitam and Wawa with their respective importance values

Total Basal Common Name Scientific Name Count DBH Area RDom Density RDen Frequency RFreq IV (cm) (m2) Bakauan Lalake Rhizophora apiculata 62 535.141 22.492 33.276 10.333 33.514 0.500 25.000 91.789 Bungalon/Pipisik Avicennia marina 35 509.135 20.359 30.120 5.833 18.919 0.667 33.333 82.372 Bakauan Babae Rhizophora mucronata 8 543.958 23.239 34.381 1.333 4.324 0.333 16.667 55.372 Langarai Bruguiera parviflora 74 93.042 0.680 1.006 12.333 40.000 0.167 8.333 49.339 Pedada Sonneratia caseolaris 6 102.336 0.823 1.217 1.000 3.243 0.333 16.667 21.127

Legend: DBH – diameter at breast height; RDom – Relative Dominance; RDen – Relative Density; RFreq – Relative Frequency; and

IV – Importance Value

Table 9. Frequency and Diversity Index of Mangrove Stand of Barangay Cuta

Common Name Scientific Name Family Frequency pi ln pi pi*ln pi Pipisik Avicennia marina (Forsk.) Vierh Acanthaceae 23 0.479167 -0.319513401 -0.153100171 Langarai Bruguiera parviflora (Roxb.) W & A ex. Griff Rhizophoraceae 6 0.125 -0.903089987 -0.112886248 Pedada Sonneratia caseoralis (L.) Engl. Lythraceae 19 0.395833 -0.402487636 -0.159318023 48 -0.425304443 Diversity Index 0.425304443

Table 10. Frequency and Diversity Index of Mangrove Stand of Barangay Malitam

Common Name Scientific Name Family Frequency pi ln pi pi*ln pi Bakauan Lalake Rhizophora mucronata Lamk. Rhizophoraceae 74 0.660714 -0.179986303 -0.118919522 Bakauan Babae Rhizophora apiculata Blume Rhizophoraceae 19 0.169643 -0.770464422 -0.130703786 Pipisik Avicennia marina (Forsk.) Vierh Acanthaceae 11 0.098214 -1.007825338 -0.098982846 Pedada Sonneratia caseoralis (L.) Engl. Lythraceae 6 0.053571 -1.271066772 -0.068092863 Nipa Nypa fruticans 2 0.017857 -1.748188027 -0.031217643 112 -0.447916659 Diversity Index 0.447916659

Table 11. Frequency and Diversity Index of Mangrove Stand of Barangay Wawa

Common Name Scientific Name Family Frequency pi ln pi pi*ln pi Bakauan Babae Rhizophora apiculata Blume Rhizophoraceae 50 0.520833 -0.283301229 -0.147552723 Bakauan Lalake Rhizophora mucronata Lamk. Rhizophoraceae 45 0.46875 -0.329058719 -0.154246275 Pipisik Avicennia marina (Forsk.) Vierh Acanthaceae 1 0.010417 -1.982271233 -0.020648659 96 -0.322447657 Diversity Index 0.322447657

Table 12. List of all species in Site 3: Barangay Tabangao with their respective importance values

Basal Total Common Name Scientific Name Count Area Rdom Density RDen Frequency RFreq IV DBH (cm) (m2) Bungalon/Pipisik Avicennia marina 151 1455.628 166.415 89.469 16.778 67.713 1.000 32.143 189.325 Pedada Sonneratia caseolaris 25 284.123 6.340 3.409 2.778 11.211 0.889 28.571 43.191 Bakauan Lalake Rhizophora apiculata 34 396.263 12.333 6.630 3.778 15.247 0.556 17.857 39.734 Bakauan Babae Rhizophora mucronata 8 70.760 0.393 0.211 0.889 3.587 0.444 14.286 18.085 Pagatpat Sonneratia alba 5 81.519 0.522 0.281 0.556 2.242 0.222 7.143 9.666

Legend: DBH – diameter at breast height; RDom – Relative Dominance; RDen – Relative Density; RFreq – Relative Frequency; and IV – Importance Value

Table 13. Frequency and Diversity Index of Mangrove Stand of Barangay Tabangao

Common Name Scientific Name Family Frequency pi ln pi pi*ln pi Bakawang Lalake Rhizophora mucronata Lamk. Rhizophoraceae 46 0.183267 -0.73691589 -0.135052314 Pedada Sonneratia caseoralis (L.) Engl. Lythraceae 35 0.139442 -0.855605677 -0.119307565 Pipisik Avicennia marina (Forsk.) Vierh Acanthaceae 144 0.573705 -0.241311229 -0.138441502 Pagatpat Sonneratia alba L. Smith Lythraceae 5 0.01992 -1.700703717 -0.03387856 Bakawang Babae Rhizophora apiculata Blume Rhizophoraceae 21 0.083665 -1.077454427 -0.090145589 251 -0.516825531 Diversity Index 0.516825531

3.3 LAND COVER / LAND USE CHANGE

Mangrove cover of Batangas City has changed over the past three decades (Table 14 and Figure 3). For instance, dense mangrove stand used to cover about 22.4 ha in 1997, and has slightly decreased by about 2.4 ha after a decade (in Year 2006). Such decrease is very much reflective of the increase in areas that were classified as open / bare coastal area, which was estimated to 11.4 ha (from 3.3 ha in 1997). Sparse or patchy mangrove sites had also decreased between 1997 to 2006 (from 1.2 ha to 0.3 ha) and most likely attributable to anthropogenic disturbances that were observed such as illegal cutting (particularly in Site 2).

By 2016, mangrove cover of both wooded / dense and sparse has increased to 26.5 ha and 1.7 ha, respectively. Such increase is likely attributable to mangrove planting activities of LGUs and energy companies (particularly in Site 1), as well as the stricter protection of sparse mangrove areas that are situated in the nearby industrial facilities (particularly in Site 3: Tabangao) where small mangrove patches had grown and expanded.

Built-up areas that are primarily comprised of industrial sites along Batangas coast had appeared to have significantly decreased over the past three decades. This change can be largely explained by the decommissioning activities of petroleum infrastructures, which are evident in Site 1 and Site 3.

Table 14. Land use and land cover area distribution of Batangas City, Philippines across three periods (1997, 2006 and 2016)

Area (ha) DRAFT Land use / Land cover type Y 1997 Y 2006 Y 2016 Wooded lands 22.4 20.1 26.5 Sparse vegetation 1.2 0.3 1.7 Open Areas 3.3 11.4 0.3 Built-up Areas 6.2 0.6 1.1

Figure 3. Land use and land cover maps of Batangas City, Philippines based on three observation periods (1997, 2006 and 2016)

3.4 BIOMASS AND CARBON STOCK 3.4.1 Site 1 (Sta. Rita and San Lorenzo)

Mangrove stand of Site 1 contains about 466.5±152.3 tC ha-1. Of this, aboveground component (stem, branches and crown) has contributed only 17.3%. Bulk (82.7%) of the carbon stock is imbedded in soil where percentage carbon content was rich at 5.7%, and depth of about 1.7m. With an area of 9.7 ha, Site 1 has the carbon stock capacity of about 4.53 ktC with an equivalent 16.59 kt CO2.

Table 15. Carbon stock capacity of Site 1 (Sta. Rita and San Lorenzo)

Plot Total Cstock CO2e Vegetation Sediment** No. (tC ha-1) (t ha-1) AGB Cstock BGB Total Depth (m) (tC/ha) (tC/ha) Cstock (tC/ha) (tC/ha)

1 71.1 23.0 94.0 2.6 541.4 635.4 2329.8 2 50.8 22.4 73.2 1.0 232.6 305.8 1121.3 3 30.7 14.0 44.7 2.3 509.8 554.5 2033.2 4 42.7 18.6 61.2 1.5 567.6 628.8 2305.6 5 72.1 32.9 105.0 1.7 226.7 331.7 1216.2 6 28.6 14.3 42.9 1.2 548.8 591.7 2169.6 7 24.1 12.0 36.1 1.3 238.1 274.2 1005.4 8 63.0 28.4 91.4 2.0 318.5 409.9 1503.0 Ave. 1.7 466.5 1710.5 47.9 20.7 68.6 397.9 SD* 0.6 157.3 152.3 558.6 19.3 7.4 26.3

*standard deviation

** Ave. percent soil carbon: 5.7%

DRAFT

3.4.2 Site 2 (Cuta, Malitam and Wawa)

Site 2 has a potential carbon stock capacity of 203.9 tC ha-1 (Table 16). With a cumulative area of 4.3 ha, this site contains a total carbon stock of about 879 tC, with an equivalent carbon dioxide storage of 3.2 k tCO2.

Vegetation contributed the larger share (61%) on this site’s total carbon stock. The small values computed for the sediment layer is reflective of the disturbed condition of this site, being situated within a densely populated river bends where some mangrove cutting and waste dumping were noted during the survey. The generally sandy and bare sediment condition has yielded a percentage carbon content of only 2.7%. The depth of sediment organic matter was measured at around 1.6 m.

Among the sampling areas, largest values were observed in Barangay Cuta (343.9 tC ha-1). This was followed by Wawa with 142. 7 tC ha-1, and lastly by Malitam with only 125.3 tC ha-1.

Table 16. Carbon stock capacity of Site 2 (Cuta, Malitam and Wawa)

Vegetation Total Cstock CO2e Site / Plot No. Sediment** -1 -1 (tC ha ) (t ha )

BGB AGB Cstock Cstock Total(tC/ha) Depth (m) (tC/ha) (tC/ha) (tC/ha)

Cuta

Plot 1 158.6 62.2 220.8 2.0 129.0 349.8 1282.8

Plot 2 127.0 51.5 178.6 3.0 159.3 337.9 1238.9

Average 142.8 56.8 199.7 2.5 144.2 343.9 1260.8

Malitam

Plot 1 65.6 33.1 98.6 1.6 73.7 172.3 631.7

Plot 2 28.0 13.9 42.0 1.0 36.1 78.1 286.3

Average 46.8 23.5 70.3 1.3 55.0 125.3 459.5

Wawa

Plot 1 99.7 47.0 146.6 1.0 38.6 185.2 679.1

Plot 2 36.5 17.8 54.3 1.0 46.1 100.4 368.0

Average 68.1 32.4 100.4 1.0 42.3 142.7 523.3

Overall Ave. 85.9 37.6 123.5 1.6 80.5 203.9 747.8

SD* 51.7 19.3 70.8 0.8 52.0 115.9 424.9

*standard deviation

** Ave. percent soil carbon: 2.7%

3.4.3 Site 3 (Tabangao)

With an estimated area of 12.5 ha, Site 3 (Tabangao) has a total carbon stock capacity of 2.76 ktC, or 10.13 -1 ktCO2. This is based on 220.9 tC ha mean estimate for this riverine site. Slightly more than half (57%) of this value is stored in sediment with as much as 125 tC ha-1.

Table 17. Carbon stock capacity of Site 3 (Tabangao)

Plot Vegetation Total Cstock CO2e Sediment** -1 -1 No. (tC ha ) (t ha )

AGB BGB Total Cstock Cstock Depth (m) (tC/ha) (tC/ha) (tC/ha) (tC/ha)

1 81.6 34.9 116.5 1.0 96.7 213.2 781.7

2 61.3 26.2 87.5 3.0 183.8 271.2 994.6

3 82.7 35.3 117.9 2.0 107.6 225.5 826.9

4 78.5 34.9 113.3 2.0 99.9 213.3 782.0

5 73.1 31.5 104.6 3.0 165.4 270.0 990.0

6 68.1 30.5 98.6 1.0 71.4 170.0 623.4

7 40.8 18.3 59.2 1.0 29.1 88.3 323.7

8 66.9 33.0 99.8 2.0 147.1 247.0 905.5

9 40.8 20.0 60.8 3.0 229.0 289.8 1062.5

Ave. 66.0 29.4 95.4 2.0 125.6 220.9 810.0

SD* 15.9 6.5 22.3 0.9 61.4 61.9 227.1

*standard deviation ** Ave. percent soil carbon: 1.6% 3.4.4 Overall Carbon Stock Assessment for 3 sites

Among the sites, largest carbon stock was observed in Site 1 (Sta. Rita and San Lorenzo) which is situated within an energy power plant facility (Figure 4). The total carbon dioxide sequestered by this site has reached about 16.59 ktCO2. This comprised the 55% of the city’s overall mangrove carbon stock. Huge value was noted at the sediment layer which is largely reflective of high percentage of carbon content i.e. 5.7%. Site 3 (Tabangao) followed with 10.10 ktCO2. Likewise, carbon was found higher sediment than in vegetation in with 125.6 tC ha-1 and 95.4 tC ha-1, respectively. This site is situated besides two petroleum refinery sites hence security and access to mangrove sites were observed tight. Finally, Site 2 which is relatively open- access to local communities has a carbon stock of only 3.22 ktCO2. In contrast with the two other sites, vegetation layer here contributed more carbon stocks with 123.5 tC ha-1, while 80.5 tC ha-1 in sediments. Such estimates are very much reflective to disturbed condition of this site.

If compared to other estimates in the country, results of this study has larger carbon stock estimates. For instance, ENFOR (2003) as cited by Gevaña et al. (2011) has reported only 139.07 tC ha-1 for a similar Avicennia–dominated in Padre Burgos, Quezon. Likewise, Gevaña et al. (2011) has indicated only 128.58 tC ha-1 for the mangroves in a nearby site of San Juan, Batangas. Estimates for Bataan and Palawan sites also showed smaller values with 117.60 tC ha-1 and 235.5 tC ha-1, respectively according to Castillo et al. (2012). Such lower values are generally reflective of the sediment carbon estimates of which measurements were only done within one meter depth.

Figure 4. Total carbon stock distribution of three mangrove sites in Batangas City, Philippines

Mangrove forest of Batangas City has a total carbon storage capacity of 29.92 ktCO2 (Figure 5). Sediment shares 71% of this stock which implies the need for serious protection of both vegetation and sediment in order to prevent this significant ecosystem goods from washing away.

Figure 5. Total carbon dioxide (ktCO2) storage capacity of Batangas City mangrove forest

3.5 SEDIMENT CARBON STOCK

Mangrove forests are one of the most important carbon sinks in the tropical ecosystem. A great proportion of its carbon stock is imbedded in the organic-rich sediment which unfortunately susceptible to emission if mangrove vegetation are disturbed. Batangas City exemplifies a good case where mangrove forest thrives amidst rapid urbanization. It is therefore very important to account how much carbon is stored in this ecosystem particularly in its sediment. This progressDRAFT report presents the sediment carbon stock of the remaining mangrove stands in Batangas City.

Sediment carbon stock of the three mangrove sites are shown in Table 18. Overall, the mean sediment carbon stock of Batangas mangroves ranged from 42.33 tC/ha to 421.56 tC/ha. The mean total value was estimated to 215.31 tC/ha.

In view of other estimates in the country, values obtained from this site were relatively higher. For instance, Abino et al. (2014) reported about 173.80 tC/ha for a natural mangrove stand in Palawan. Further, Gevaña et al. (2008) reported only about 11.95 tC/ha for the mangrove sites in San Juan, Batangas for sediments within the 30 cm soil depth. Moreover, the results of the study are considerably higher compared to values obtained in 1m soil depth in Okinawa, Japan (57.3 MgC/ha – Khan et al., 2007) and Northern Vietnam (68.5 MgC/ha – Nguyen et al., 2009). However, the obtained soil carbon stock in the study was much lower than the values recorded in North Sulawesi (822.1 MgC/ha) with an average depth of 1.22 m (Murdiyaso et al., 2009).

The highest carbon stock was noted in Site 1 (Sta. Rita & San Lorenzo) with 421.56 MgC/ha, while the lowest was observed in Site 2 particularly Barangay Wawa (42.33 MgC/ha). The details of per plot carbon stock calculation is presented in Tables 19-21.

Overall, the total sediment carbon stock of Batangas City mangroves is estimated to about 5.9 ktC. This can be translated to as much as 21.4 ktCO2, hence a significant amount of ecosystem benefit that needs to be conserved.

Table 18. Soil carbon stock of mangrove stands in different barangays in Batangas City

Mean Total Carbon Average Area Carbon Total Carbon Dioxide Site Soil Depth (ha) Stock Stock (tC) Equivalent (m) (tC/ha) (t CO2) Malitam 0.90 2.5 144.16 129.75 475.74 Cuta 2.40 1.3 55.02 132.05 484.18 Wawa 1.10 1 42.33 46.56 170.72 Sta. Rita 9.60 1.79 421.56 4,046.97 14,838.91 Tabangao 12.47 2 125.56 1,565.68 5,470.82 Total 26.47 -- 788.63 5,921.01 21,440.37 Mean 8.82 1.72 215.31 2,047.15 7,506.20

The details of sediment carbon stock for Site 1 (Sta. Rita and San Lorenzo) is presented in Table 19. Site 1 has an area of 9.7 hectares. Values ranged from 226.73 tC/ha to 567.62 tC/ha, with a mean of 397.94 tC/ha. The highest concentration was noted in Plot 3 while the lowest is in Plot 4. Overall, this site has a mean total sediment carbon stock of 3.86 ktC hence an equivalent carbon dioxide stored of about 14.15 ktCO2.

Table 19. Sediment carbon stock of mangrove stands in Site 1(Sta. Rita and San Lorenzo)

Site Area Plot Soil Carbon Stock Total Carbon Total Carbon (ha) # Depth (m) (tC/ha) Stock (tC) Dioxide Equivalent

(t CO2)

Site 1 9.7 1 2.6 541.40 5251.58 19257.54 (Sta. Rita 2 1 232.60 2256.22 8273.56 and San 3 2.3 509.80 4945.06 18133.54 Lorenzo) 4 1.5 567.60 5505.72 20189.48 5 1.7 226.70 2198.99 8063.70 6 1.2 548.80 5323.36 19520.76 7 1.3 238.10 2309.57 8469.19 8 2 318.50 3089.45 11329.01 Mean 1.70 397.94 3859.99 14154.60

Table 20 shows the sediment carbon stock distribution in Site 2 (Malitam, Cuta and Wawa). Estimates for this cluster ranged from 36.07 tC/ha to 159.28 tC/ha. Soil depth across plots ranged from 1m to 2.5m. The mean sediment carbon stock were: 144.16 tC/ha for Malitam, 55.02 tC//ha for Cuta; and 42.33 tC/ha for Wawa. The mean total carbon stock stored in Malitam was 129.75 tC with an equivalent value of 475.74 tCO2. For Cuta, mean carbon stock estimate was about 132.05 tC which is equivalent to 484.18 tCO2. And finally, Wawa has a mean carbon stock of 46.56 tC. This is equivalent to 170.72 tCO2.

Table 20. Soil carbon stock of mangrove stands in Barangays Malitam, Cuta and Wawa

Total Carbon Average Dioxide Carbon Total Carbon Site Area (ha) Plot # Equivalent Stock (tC/ha) Stock (tC) Soil Depth (m) (t CO2)

Malitam 0.90 1 2 129.04 116.14 425.83

2 3 159.28 143.59 525.64

Mean 2.5 144.16 129.75 475.74

Cuta 2.40 1 1.6 73.68 176.82 648.35

2 1 36.07 87.28 320.02

DRAFT Mean 1.3 55.02 132.05 484.18

Wawa 1.10 1 1 38.60 42.46 155.70

2 1 46.05 50.66 185.74

Mean 1 42.33 46.56 170.72

Table 21 presents the estimates for Site 3 (Tabangao). Sediment carbons stock was found at 29.11 tC/ha to 229.01 tC/ha, with an average of 125.56 tC/ha. The highest value per plot was observe in Plot 9 (229 tC/ha) while the lowest is in Plot 7 (29.1 tC/ha). The mean total carbon stock stored in this site reached as much as 1,565.68 tC with an equivalent amount of 5,470.82 tCO2.

Table 21. Soil carbon stock of mangrove stands in Barangay Tabangao

Site Plot # Carbon Total Carbon Area Soil Total Carbon Stock Dioxide

(ha) Depth (m) (tC/ha) Stock (tC) Equivalent

(t CO2)

1 1 96.68 1205.61 4420.56

2 3 183.75 2291.30 8401.45

3 2 107.57 1341.40 4918.47

4 2 99.94 1246.31 4569.82

Tabangao 12.47 5 3 165.43 2062.96 7564.17

6 1 71.39 890.23 3264.17

7 1 29.11 363.00 1330.98

8 2 147.11 1834.50 6726.51

9 3 229.01 2855.79 10471.22

Mean 2 125.56 1,565.68 5,470.82

3.6 POTENTIAL ECONOMIC VALUE OF CARBON STOCKS

Based on the current and prevailing trading price of USD 3.3 per tCO2 in the voluntary market modality (Hamrick and Goldstein, 2016), the carbon stocks of Batangas City mangroves is worth about USD 98,149. Largest share (47%) was noted for the sediment particularly in Site 1 which amounts to USD 46,220. The whole carbon stock of Site 1 worth about USD 54,189. Site 3 followed with USD 33,346, then by Site 2 with USD 10,614.

3.7 POTENTIAL MANGROVE REHABILITATION SITES

Potential sites for future mangrove rehabilitation was roughly estimated to 504 ha (Figure 5). These sites were selected based on the following criteria: 1) open areas within existing mangrove forests; 2) bare tidal mudflats; 3) shallow frontage zones of industrial infrastructures; 4) outlet of river and creeks; 5) elevated sandy coasts suitable for beach forest species planting; and 6) preferably classified as forestland (state-owned). Possible rehabilitation site for Sta. Rita (Site 1) was about 49.5 ha that is situated beside an existing energy generation facility. About 5 ha can be established as a reforestation site in the river outlet of Barangay Cuta (Site 2). Tabangao (Site 3) still has 36.3 ha of open areas for mangrove planting. Other potential sites along the Batangas coast were estimated to 413.3 ha. These areas are primarily mudflats and sparse mangrove stands.

Pursuing a mangrove rehabilitation project will surely augment the current carbon stock capacity of Batangas City. Using the mean carbon stock estimates obtained from the three sites, these areas could have an overall potential capacity of 177.1 ktCO2 (for vegetation) and 372.1 ktCO2 (for sediment). Such values worth a ballpark amount of USD 1.81 million.

DRAFT

Figure 6. Potential mangrove rehabilitation sites in Batangas (Source: Google Earth ver. 7.1.2.2019)

V. IMPLICATIONS OF THE STUDY

The evaluation of the carbon stocks in the three mangrove sites in Batangas conveys several important implications in support of mangrove conservation and rehabilitation agenda of the country.

Low species diversity. Floristic diversity of Batangas City mangroves is generally low. This is reflective of natural and anthropogenic factors that were observed. First, natural factors include the ability of mangroves to naturally grow and predominate certain habitats i.e. largely determined by sediment and tidal conditions. This is common in the case of: Rhizophora spp. (Site 2) which are naturally growing along riverine areas; Avicennia spp. on shallow tidal mudflats (Site 1); and Sonneratia spp. on subtidal coasts (Site 3). Gevana and Pampolina (2009) observed a similar case in San Juan, Batangas. Secondly, environmental factors such as tidal changes and exposure to sunlight and wind are also important determinants of species composition and diversity. In terms of anthropogenic factors, those activities that lead to deforestation or degradation of mangrove cover and sediments have likely decreased the floristic diversity and density of mangrove stands. These activities largely include illegal tree cutting (all three sites), conversion of mangroves to settlement areas (Site 2), and waste dumping (Site 2). In sum, the survival and composition of mangrove stands depend on plants ability to cope with these disturbances. Among the sites, diversity index was highest in Site 1 being situated in a secured power plant facility, while lowest in Site 2 where human disturbances (such as cutting and waste dumping) were observed rampant. This observation calls for a more strengthened policy enforcement and increased community awareness and involvement in rehabilitation programs.

Rich sediment carbon stocks. Mangrove performs the vital role of filtering and capturing organic materials from the midstream and upstream ecosystems, and avoid them from harming the seagrass and coral beds. Since most of the nearby upstream towns of Batangas City are primarily of agricultural land use, it is expected that sedimentation and organic matter deposition to Batangas City coast is very high. Evidently, large sediment carbon stock values were observed particularly in Site 3. This implies the need for serious forest protection efforts in order to save and augment these stocks. If deforestation and degradation (particularly through waste dumping) will continue, such critical ecosystem functions will surely be impaired.

Economic potential of carbon stocks. Ecosystem valuation provides the rationale of putting forward mangrove conservation in Batangas City. With the huge economic value of mangrove carbon stock observed, coastal protection and rehabilitation should be one of the priority programs of the local government for the environment. Such economic potential also indicates the opportunity of pursuing incentive-based conservation programs such as carbon offset projects (e.g. REDD Plus) in the future.

Need for sound rehabilitation. Batangas City has potential spaces for mangrove reforestation. In pursuing coastal rehabilitation, plans and efforts should aim at increasing floristic diversity and reviving important ecosystem services such as carbon sequestration. Samson and Rollon (2008) conducted an extensive assessment of the growth and survival of monoculture or single-species plantations in Southern Luzon, Central Visayas and Mindanao. They reported that reforestation sites that were planted with pure Rhizophora spp. yielded dismal outcomes i.e. high mortality and poor growth performance. Such result was also linked to the weak adaptability of species to their non-natural habitat. Addressing this issue will truly require proper guidance on rehabilitation works. Mix species planting which adheres to site-species suitability matching must be followed in the future rehabilitation works in Batangas City. Participatory mangrove rehabilitation should

intimately involve local government, local communities and private industries (particularly energy, petrochemical and seaport establishments).

Enforcement of environmental laws. Mangrove deforestation and degradation problems in Batangas City are reflective of the limited enforcement of environmental laws such as the Republic Act 7161 (which bans mangrove cutting) and Republic Act 9003 (Solid Waste Management Act). Similarly, the conversion of mangroves to industrial land uses was also noted as apparent issue which is indicative of limited compliance of industries to the mitigation plans that are stipulated in their Environmental Impact Assessment / Studies document. Addressing these limitations would require crafting of local policies, enforcement of existing ones, and institutionalization of individuals / groups from the local government and non-government sectors (who will monitor compliance).

Moreover, coastal areas that are originally classified as forestland should be rehabilitated and this requires a review and validation of old forestry maps and thereafter strengthened rehabilitation efforts over these sites through Provincial or Municipal resolutions.

Strengthening partnership through co-management approach. The findings strongly suggest that the City government of Batangas and the local barangays who are in charge of the management of the mangrove sites should tie-up with private companies who are, on the other hand, adjacent to these said mangrove sites. The numerous ecosystem services found in mangrove areas made it very suitable for development projects which explains the presence of adjacent private companies. For instance, the mangrove sites in Site 1 (Sta. Rita and San Lorenzo) are located next to private companies that generate energy-related products. However, possible ramifications during the company’s service span arising from their dependence or proximity to mangrove areas could occur, among which are degradation and pollution that could possibly inflate if not properly accounted. These risks to environmental health should be addressed by the concerned businesses to avoid business threats and for continuous harvest of benefits.

DRAFT One way to engage these private companies in mangrove conservation and rehabilitation is to develop management strategies that would establish linkage between business targets and environmental health and in the process complement each other. Corporate Ecosystem Services Review (CESR) as a tool to help integrate business and environmental is gaining popularity among development projects that make use of ecosystem services and/or near to a natural resource. CESR is a general framework that includes guidelines for industries on how to assess environmental impacts based on their level of dependence on a particular natural resource and highlights the actions on how to address negative implications on the environment.

Through the introduction of CESR to the concerned businesses, the benefits they could derive if they would integrate such tool in their management system should be emphasized and highlighted in order to encourage them to enter into the partnership of mangrove management. If the City government of Batangas would gain the support and involvement of these private companies, particularly those near mangrove areas, this would greatly advance the conservation and rehabilitation of mangroves in the province.

Pursuing co-management of mangroves will aid in raising local commitment on forest conservation and rehabilitation.

Opportunities towards green growth. The computed value of carbon stock can be used to rationalize the path towards green growth. The findings of this study would give purpose to the conservation and rehabilitation efforts of the Batangas City government and eventually aid on their future investment on programs that promotes sustainable use of mangrove resources and services. The potential of mangroves to store large amount of carbon also suggests another mechanism to mitigate the effects of climate change. This strongly support the importance of keeping mangrove areas intact through conservation and the improvement of existing environmental regulations and policy implementation in Batangas province.

In the process of attaining green growth, benefits derived from mangrove areas is expected to increase. The increase in benefits should be maximized in a way that is sustainable and it satisfies the three pillars of green growth: social equity, environmental acceptability and economic viability wherein addressing climate uncertainties should be integrated to obtain a holistic approach.

VI. CONCLUSION AND RECOMMENDATIONS

A low species diversity was observed in the three study sites in Batangas City which are attributed to natural factors and a number of anthropogenic factors such as tree cutting and waste dumping which are specifically observed in Site 2 where there is a corresponding low species diversity observed. Nonetheless, the carbon stock computed in the three sites were found to be significantly high suggesting that mangroves are generally good carbon sinks. Further mangrove conservation and rehabilitation efforts that will increase floristic diversity and carbon storage of each individual stand would be a good contribution to mitigate global warming and climate change.

Moreover, the observed high potential of mangroves for carbon storage translates into high economic value. This could be further improved with sound and effective management interventions stemming from the local government, concerned local communities, and private institutions benefitting from mangrove services towards the prevention of deforestation and pollution from human activities. These future management initiatives and policy enforcement to be undertaken by the local government and other stakeholders should paved the way towards the sustainable use of mangroves’ ecosystem services and eventually to the increased harvest of its benefits. Lastly, it is recommended that results of this study should be considered in mainstreaming natural capital accounting and green growth initiatives in policy formulation and decision- making. DRAFT

VII. ANNEXES

ANNEX 1. SEDIMENT SAMPLING ACTIVITIES IN VARIOUS MANGROVE SITES OF BATANGAS CITY

DRAFT

ANNEX 2. PARTIAL LIST OF MANGROVE SPECIES IDENTIFIED FOR SITE 2: BARANGAY CUTA, MALITAM AND WAWA WITH THEIR IUCN CONSERVATION STATUS, ECONOMIC IMPORTANCE AND THREATS

IUCN Scientific Name Conservation Economic Importance Threats Status

Domestic Consumption Avicennia Domestic consumption; Loss (food, fodder, fuelwood, marina (Forsk.) Least Concern of Mangrove habitat due to construction materials and Vierh. coastal development medicine) Domestic Consumption (food, forage, fuelwood, construction materials for building houses andl boats, Domestic consumption; Loss Sonneratia Least Concern also as medicine); of Mangrove habitat due to caseolaris (L.) Engl. pneumatophores used as coastal development floats and for cork-making; tannins from bark used as dyes Domestic consumption; Loss Nypa Not Yet Domestic Consumption of Mangrove habitat due to fruticans Wurmb. Assessed coastal development Bruguiera This species may be Domestic consumption; Loss parviflora (Roxb) Least Concern attractive to timber extraction of Mangrove habitat due to W. & A. ex Griff. as it grows very straight. coastal development Commercially exploited for Domestic consumption; Loss Rhizophora Least Concern charcoal; It is a highly prized of Mangrove habitat due to mucronata Lamk. construction wood. coastal development Commercially exploited for Domestic consumption; Loss Rhizophora Least Concern charcoal; It is a highly prized of Mangrove habitat due to apiculata Blume construction wood. coastal development

ANNEX 3. PARTIAL LIST OF MANGROVE SPECIES OF BARANGAY TABANGAO WITH THEIR IECN CONSERVTATION STATUS, ECONOMIC IMPORTANCE AND THREATS

IUCN Scientific Name Conservation Economic Importance Threats Status

Domestic Consumption (food, Domestic consumption; Avicennia fodder, fuelwood, Loss of Mangrove habitat marina (Forsk.) Least Concern construction materials and due to coastal Vierh. medicine) development

Domestic Consumption (food, fuelwood, construction Domestic consumption; Sonneratia alba L. materials for building houses Loss of Mangrove habitat Least Concern Smith and boats, also as medicine); due to coastal pneumatophores used as development floats and for cork-making

DRAFT Domestic Consumption (food, forage, fuelwood, construction materials for Domestic consumption; Sonneratia building houses and boats, Loss of Mangrove habitat caseolaris (L.) Least Concern also as medicine); due to coastal Engl. pneumatophores used as development floats and for cork-making; tannins from bark used as dyes

Domestic consumption; Commercially exploited for Rhizophora Loss of Mangrove habitat Least Concern charcoal; It is a highly prized mucronata Lamk. due to coastal construction wood. development

Domestic consumption; Commercially exploited for Rhizophora Loss of Mangrove habitat Least Concern charcoal; It is a highly prized apiculata Blume due to coastal construction wood. development

ANNEX 4. RESEARCH TEAM

From University of the Philippines DR. MARIA VICTORIA O. ESPALDON DR. RICO C. ANCOG DR. DIXON T. GEVAÑA FOR. ROMNICK S. BALITON FOR. MICHAEL JOSEPH SM. PILLAS FOR. ARTHUR GLENN A. UMALI MS. MA. KRISTINA OQUIŇENA - PALER

From Batangas City Environment and Natural Resources Office MR. PAULO FAJILAN MR. RANDY ARGUELLES MR. ODELON CONTI, JR. MR. CARLO DELGADO

ANNEX 5. LITERATURE CITED

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Castillo, JA. A. and L.A. Breva. 2012. Carbon Stock Assessment of Four Mangrove Reforestation/Plantation Stands in the Philippines. Proceedings of the First ASEAN Congress on Mangrove Research and Development. ISSN: 2350-6865

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Polidoro, B., Carpenter, K., Collins, L., Duke, N., Ellison, A., Ellison, J. Farnsworthm E., Fernando, E., Kathiresan, K., Koedem, N., Livingstone, S., Miyagi, T.,Moore, G., Ngoc Nam, V., Eong Ong, J., Primavera, J., Severino, S., Sanciangco, J., Sukarddjo, S.Wang, Y. and J. Wan Hong Yong. 2010. The Loss of Species: Mangrove Extinction Risk and Geographic Areas of Concern of Global Concern. Plos One. 5(4):e10095.

Sinfuego, K. and I. Buot. 2014. Mangrove zonation and utilization by the local people in Ajuy and Pedada Bays, Panay Island, Philippines. Journal of Marine and Island Cultures. 3:1-8.

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