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Bull. Soc. Sea Water Sci., Jpn., 65, 3－ 9（2011）Bulletin of the Society ofSea Water Science, Japan

Special Issue: Measures to the Global Environment Problems（Review）

Mangroves for the People and Environmental Conservation in Asia

Sanit AKSORNKOAE＊ 1 and Shigeru KATO＊ 2

Abstract　Mangroves are among the most signifi cant and valuable coastal ecosystems providing considerable benefi ts, many goods and ser-vices, to humans through forest products, fi sheries and medicines. In addition and importantly, they play a major role in ecological and natural disaster protection in coastal areas. Asian people have used mangroves in their lives and economies over a long period of his-tory. Unfortunately, mangrove forests in this region have been under threat of severe destruction especially since the 1980’s due to confl icting development purposes. Encouragingly, the mangrove forests areas of Southeast Asia slightly increased while those in south Asia and East Asia have slightly declined over the past decade. Today, intensive management of mangrove forests in Asian countries is evident, especially rehabilitation, protection and conservation. The sustainable management of mangrove forests will not be achieved without close participation of all stakeholders strong technical supporting and strict law enforcement by Governments who look upon their mangrove ecosystems as excellent resources for a world that must fi nd ways of placing a dollar value on natural eco-resources.

Key Words : Mangrove, Biodiversity, Carbon sink, Ecosystem

＊ 1 Faculty of Forestry, Kasetsart University, Professor Emeritus, 50 Ngamwongwan Rd., ChatuChak, Bangkok 10900, Thailand＊ 2 Department of Materials and Life Science, Faculty of Science and Technology, Seikei University, 3-3-1, Kichijoji-Kitamachi, Musashino-shi,

Tokyo 180-8633 Japan

1．Introduction

Mangroves are among the most significant and highly productive coastal ecosystems in the tropical and subtropi-cal regions of the world. They are generally restricted to the inter tidal zones from the lowest low water level （neap tide） to the highest high water level （spring tide）.

In Asia, mangrove forests of varying sizes are distributed in three regions and eighteen countries. There are fi ve coun-tries, Bangladesh, India, Maldives, Pakistan and Sri Lanka in South Asia; ten countries: Brunei Darussalam, Cambodia, Indonesia, Malaysia, Myanmar, Philippines, Singapore, Thai-land, Timor-Leste and Vietnam in Southeast Asia. In East Asia, we have the two countries, China and Japan and the island of Taiwan.

Mangrove resources are highly productive in terms of hu-man utilization. Mangrove plant products are diverse with uses ranging from timber, poles, fi rewood, charcoal, fodder, thatching, bark and medicines. The ecological role of man-groves is varied. Mangroves provide food, habitats, feed-ing, nursery and spawning grounds for many commercial aquatic fauna and also habitats for some terrestrial animals. The environmental protection functions of mangroves have been recognized also. These include the important roles of trapping sediment, preventing or reducing coastal erosion, dispersing the energy of tidal waves and reducing global

warming by acting as a Carbon sink.The mangroves in Asia perhaps most noticeably in South-

east Asia have been heavily reduced during the last three decades. However, many countries have properly formulat-ed the national mangrove policy which includes rehabilita-tion, conservation and sustainable utilization. Currently, the intensive management of mangroves in many countries is being attempted and or implemented for the long term ben-efi ts of human needs and ecological resource protection. In-creasingly, it seems, that mangroves in Asia are looked upon as resources deserving wise use. This trend is favourable but contrasts with an opposite trend emerging in the South Pacific country of New Zealand where mangrove stands have been attacked by both developers and even some lo-cal Governmental organizations who see the spread of New Zealand’s unispecifi c stands of the mangrove Avicennia ma-rina as a problem and in confl ict the wishes of pleasure boat marinas1）.

2．Mangrove Areas and Distribution

The current extent of mangrove forests around the world is approximately 152,000 km2 2）. They are widely distributed throughout S. E. Asia and along the coasts of the Indian ocean and Western Pacifi c ocean with a total area of some 61,607.03 km2 or 40.5 percent of the total mangrove area of the world. Mangrove forests in Asia were found in three

Bull. Soc. Sea Water Sci., Jpn., Vol. 65, No. 1 （2011）4

different regions, Southeast Asia, South Asia and East Asia with 17 countries, namely, Brunei Darussalam, Cambodia, Indonesia, Malaysia, Myanmar, Philippines, Singapore, Thai-land, Timor-Leste, Vietnam, India, Maldives, Pakistan, Sri Lanka, China （including Taiwan） ［It is most important that we do not talk of Taiwan as a separate country. It is a special province of China］ and Japan. The largest area of man-groves in Asia is found in Indonesia due to a long muddy coastline and many islands with diverse habitats3）. Table 1 shows the details of extent of mangrove forests in different countries of three regions in Asia.

3．Mangrove Ecosystem Services

Mangrove ecosystems provide many socio-economic ben-efi ts and protection of coastal ecosystem resources. In Asia, more particularly in Southeast Asian countries, mangrove forests are important sources of both timber and non-timber products which generate a livelihood for many people in coastal areas and thus contributing to the economy of the country. The detailed utilization of mangroves as both tim-ber and non-timber products are given below.

Timber, fuelwoods, poles and high quality charcoal are mainly extracted from Rhizophora species4）. Wood chips from mangrove trees in Indonesia are exported to Japan and Taiwan5）. Tannin from Rhizophora, Bruguiera and Ceriops are wildly used for dying materials （in cloth, fishing nets and even small fishing boats） in many counties of South-east Asia and in Okinawa, Japan6）. Propagules of Bruguiera species are used in the cookie-baking industry of Thailand. Nipa is used for many purposes （e.g. leaves for wrapping to-bacco and thatching, fruits for eating, sap for making sugar） 7）. Many species of mangrove plants are used for medicines by local people8, 9）. Avicennia leaves are widely use for ani-mal feeding in India10） and as fodder for cattle in Pakistan11）. Mangroves are a signifi cant food source particularly marine

animals such as prawns, fi sh, crab and molluses and these products are not only for local consumption but also for commercial purposes.

The ecological roles of mangrove ecosystems are many and varied. Mangroves serve as good nurseries, spawn-ing ground and feeding habitats of fishes, crabs, shrimps and molluses12）. They also play a very significant roles in trapping sediment and pollutants in biological fi ltering, dis-persing the energy of cyclonic storm and tsunami waves, reducing coastal erosion13, 14, 15）. In addition and impor-tantly, mangrove forests have great biomass productivity and play a very signifi cant role in carbon sequestration not only above ground but also below ground 16）. Indeed, their below ground biomass can be greater than above ground biomass17, 18）, an attribute that makes them of outstanding importance in global efforts to use trees as mitigation tools in CO2 capture and long term storage.

In many countries of Asia, mangrove forests are used for biological conservation, education and research, ecotour-

Table 1　The extent of mangrove forests in different countries of three regions in Asia.Southeast Asia South Asia East Asia

countries Area, km2 countries Area, km2 countries Area, km2

Brunei Darussalam 173.10 Bangladesh 4,951.36 China 207.56Cambodia 728.35 India 4,325.92 Taiwan NAIndonesia 31,893.59 Maldives NA Japan 7.44Malaysia 7,097.30 Pakistan 977.34Myanmar 5,029.11 Srilanka 88.82Philippines 2,564.82Singapore 4.60Thailand 2,483.62Timor-Leste 18.02Vietnam 1,056.08Total 51,048.5 10,343.44 215

Source : M. Spalding, et al., 20102）

Fig. 1　Mangrove wood for fi rewood and charcoal production

S. AKSORNKOAE, S. KATO：Mangroves for the People and Environmental Conservation in Asia 5

ism, and as wildlife sanctuaries19）. Figs.1-4 illustrate the ex-amples of mangrove values.

4．Mangrove Environment

Mangrove forests are generally found along the coast-lines. They tend to be restricted to special environmental conditions: where sedimentation can occur in low wave en-ergy coastal situations. The structure and function of man-grove ecosystems are strongly infl uenced by combinations of important environmental factors7, 20, 21） and these consist of coastal geomorphology including （topography, types e.g. delta, lagoon, mudfl at）, climate （especially temperature and wind）, tidal conditions （tidal range, tidal duration）, waves and currents （speed and direction）, salinity （soil and sea

Fig. 3　Mangrove forests for tsunami protectionFig. 2　Bruguiera’s propagules for cake baking

Fig. 5　 Mangrove forest in Okinawa, Japan with a relatively small difference between low and high tidal regimes

Source : K. Sato＊ , K. Munetake＊＊ and Y. Tateda＊＊＊＊ Faculty of Agriculture, University of the Ryukyus, ＊＊ Co. Air-Graph, ＊＊＊ Environmental Science Research Laboratory, CRI-EPI

Fig. 4　Food chain from a mangrove forest ecosystem

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water interactions with fresh water systems）, nature of the soil, drainage aeration, dissolved oxygen and redox status of the mud22） and nutrients （both inorganic and organic）. Fig.5 and Fig.6 illustrate two different mangroves forest systems which have contrasting tidal ranges.

5．Mangrove Biodiversity

Mangrove forests can be very diverse in terms of ecosys-tem structure with different habitats within the same eco-system supporting a variety of fl ora and fauna ranging from marine, freshwater and also terrestrial species. The ecotonal importance of mangrove ecosystems as unique ecosystems between terrestrial and estuarine or marine habitats has been a Conference theme and the subject of many papers23）. Giesen and Wulffraat （1998） recorded that mangroves in Asia, particularly in Southeast Asia, are the best developed and probably the most biodiverse in the world24）. Tomlinson （1986） made a similar claim and highlighted the regions

richness in species biological diversely.A list of mangrove species in Southeast Asia has been

recorded for various countries. There are 53 genera and 74

species belonging to 35 families of trees and shrubs in man-grove forests in Thailand25, 26）. Around 80 species belonging to 68 families in mangroves in the Philippines27）. In Indo-nesia, mangrove forests probably have the greatest plant species diversity in the world according to Soemodihardjo3） who recorded 91 plant species of which 37 were trees, 5 were shrubs, 3 were palms and 9 were lianas. In addition, 29 epiphytic and 2 parasitic species were recorded, along with around 6 unspecifi ed species within ‘undergrowth’. Similar species biodiversities have been reported in Thailand26）. The dominant tree species in Asian mangrove forests belong to 8 genera: Rhizophora, Bruguiera, Ceriops, Avicennia, Sonnera-tia, Xylocarpus, Lumnitzera and Excoecaria. Nipa palm is also abundant in these mangrove forests.

The animal communities in mangrove forests can be broadly divided into two components, the essentially aquatic fauna includes fi shes, shrimps, crabs and molluscs, and the mostly terrestrial animals including birds, reptiles, amphib-ians, mammals and insects. There are several studies in vari-ous countries in Asia on aquatic fauna in mangrove forests which have shown that the species and number of species are similar. UNDP/UNESCO recorded that the aquatic faunal communities in Asian countries are very rich and diverse including 72 species of fi shes, 30 species of crabs, 26 species of molluscs and 15 species of shrimps4）. The recently published book on the Rice fish of Asia includes much new information on Oryzias fi sh biodiversity and ecol-ogy, including the presence of two species of this small but scientifi cally outstanding fi sh in the mangrove ecosystems of S.E. Asia28）. Findings such as these illustrate that we still have more to discover in mangrove ecosystem biodiversity.

Beside the above-mentioned group of animals, there are also a number of organisms in mangrove ecosystem that play a critical role in litter decomposition. This group includ-

Fig. 6　 Mangrove in Peninsula Thailand with relatively high dif-ferences between low and high tide

Fig. 7　Samples of Tree species from Asian mangrove forests Fig. 8　Samples of Fish species in Asia mangrove forests

S. AKSORNKOAE, S. KATO：Mangroves for the People and Environmental Conservation in Asia 7

ed fungi, bacteria, polychaetes, nematodes and meofauna. Examples of fl ora and fauna in mangrove forests illustrate in Fig.7 to Fig.10.

6．Mangrove Degradation and Depletion

Mangrove forests in many countries in Asia have been and continue to experience on-going threats of destruction. In the past, especially during the rapid expansion of shrimp farming in converted former mangrove habitats, mangrove destruction reached alarming levels. These destructive trends have similar patterns in Asia and it is useful to clas-sify them into 10 categories. These development activities include aquaculture, mining, agriculture, urbanization, ports and harbours, roads and transmission lines, dredging,

industry and power plants, salt production and excessive harvesting of forest products7）. Typical examples of man-grove destruction are illustrated in Fig.11 and Fig.12. The total area of mangrove lost in Asian countries over different time spans （1980-2000） has been estimated by FAO29）. This loss was reassessed by Spalding2）. Details of estimated man-grove loss （or gain） in areas over the past three decades are shown in Table 2. The area of mangroves has been reduced approximately 21 percent during the 30 years from 1980 to 2010 （Table 2）. However, the trend of mangrove area loss slightly declined in the past decade as compared to the years between 1980 and 2000. In Southeast Asia, in particular, the mangrove areas slightly increased from 50,021 km2 in 2000

Table 2　 Estimated mangrove areas in Asia by regions during different time spans.

RegionMangrove area, km2

1980 1990 2000 2010Southeast Asia 63,893 55,191 50,021 51,049South Asia 12,893 11,433 10,912 10,343East Asia 350 291 238 215

Sources : FAO, 2006 and M. Spalding et al., 2010

Fig. 9　Samples of Shrimp species in Asian mangrove forestsFig. 10　 Representative Crabs and molluscs species in Asian

mangrove forests

Fig. 11　 New total conversion of mangrove forest to shrimp ponds: notice the limited retention of mangrove belts between ponds

Fig. 12　 Conversion of mangrove forest to resettlement area, perhaps following a natural disaster (e.g. cyclonic storm) or economic forces attracting new settlement

Bull. Soc. Sea Water Sci., Jpn., Vol. 65, No. 1 （2011）8

to 51,049 km2 in 2010. The increasing of mangrove forest areas in the past decade is mainly due to the success of re-habilitation programmes and effective mangrove protection. This is most encouraging and, as mentioned above, the ef-forts evident for S.E. Asia in rehabilitation tend to contrast with those of New Zealand where a relatively new trend of both planned and illegal mangrove removal has emerged1）.

7．Sustainable Mangrove Management

Mangroves constitute a rich and diverse ecosystem which, however, due to inproper management practices, has suffered severe and wide spread degradation. Intensive management of mangrove is essential today and the follow-ing three main actions will facilitate this aim.

1．Mangrove rehabilitation. Due to the tremendous in-crease in demand for fuel wood, poles, charcoal and wood chips and also for ecological protection and for maintaining the mangrove ecosystem function, the establishment of man-grove plantations must be implemented on a well planned and country-wide scale. In Asia, many countries have active-ly planed for large-scale plantations such as in Bangladesh, Thailand, Vietnam, Philippines and Pakistan. The planting areas are vary size and include degraded mangrove areas, open mudfl ats and abandoned shrimp ponds. The mangrove plantations in each country are vary in success rates. For ex-ample, successful mangrove plantation in abandoned shrimp ponds can be found under the Green Carpet Project （Fig.13） in Thailand.

2．Mangrove protection. In Asia, all mangroves belong to state or Government ownership. Mangrove protection in this region is generally ineffective due to lack of man-power, shortage of funds and weak law enforcement. The mangrove areas in many countries, therefore, are under severe destruction from illegal cutting and encroachment.

Recognizing this situation, many countries have set a long-term protection framework for effective protection of their remaining mangrove areas.

3．Mangrove resource utilization. Due to diverse uses of mangrove ecosystems an integrated management approach needs to be implemented in order to achieve a sustained yield basis. There are several examples of best practices in Asian countries for conserving mangrove along with other ecologically based purposes such as “Silvo-fi shery system” in Indonesia, Thailand and Vietnam.

The success of these three main actions mentioned above needs the participation and building of broad networks from all stakeholders to mobilizing these activities30）. Fig.13 and Fig.14 illustrate the participation of key stakeholders in mangrove planting and such action can be found in various countries in Asia.

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Atlas of Mangroves”, p. 155 （2009）, in M.Spalding et al., World Atlas of Mangroves Earthscan （2010）

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Fig. 14　 Participation of local people in mangrove rehabilitation in Thailand

Fig. 13　 Mangrove rehabilitation in abandoned shrimp ponds in Thailand

S. AKSORNKOAE, S. KATO：Mangroves for the People and Environmental Conservation in Asia 9

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（平成 22年 12月 6日受付Received December 6, 2010）