Encyclopedia of Coastal Science

Living Edition
| Editors: Charles W. Finkl, Christopher Makowski

Asia, Eastern, Coastal Ecology

  • Donald MacintoshEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-48657-4_15-2

Coastal Geography

Extending from Bangladesh in the west, to the Korean Peninsula and Siberia in the northeast (latitudes 89–129 E), Eastern Asia lies within the Indo-West Pacific Biogeographical region described by Ekman (1967). Eastern Asia contains diverse coastal land formations and habitats, ranging from rocky shores and sandy beaches, to coral reefs, seagrass beds, salt marshes, mudflats, and mangrove swamps. The main landmass of Eastern Asia includes long, uninterrupted coastlines, for example, the coast of Rhakine (Arakan) in Myanmar, the coastlines of central Vietnam and China, and the peninsulas of Malaysia and Korea. The region also supports immense archipelagoes, most notably those making up Indonesia and the Philippines, which comprise of more than 13,700 and 7000 islands, respectively. Innumerable small islands make up the Mergui Archipelago extending from Myanmar to Thailand, the Andaman and Nicobar Islands, and several minor archipelagoes. Huge deltas have also been formed by some of the world’s great rivers (the Ganges– Brahmaputra in Bangladesh, the Irrawaddy in Myanmar, the Red River and Mekong River in Vietnam, the Yangtze River and Yellow River in China).

Climate and Ecology

Climatically, Eastern Asia features a tropical equatorial subregion consisting of Malaysia, Singapore, Sumatra, Java, and Borneo; and northern subtropical to temperate subregions, which include the Bay of Bengal, the South and East China Seas, and the Yellow Sea (Fig. 1). The Malay-Indonesia region has a hot and humid climate and is bathed by shallow, highly productive seas overlying the Sunda Shelf (the submerged peninsula of Pleistocene Sundaland). Extensive coastal areas of the Sunda Shelf are less than 60 m in depth. The Philippines borders the eastern edge of the Sunda Shelf, with much deeper waters of the Pacific Ocean beyond. Although the southern archipelago of Indonesia lies mainly within the humid tropical zone, there are some subhumid to semiarid areas, particularly to the east, including the northeast coast of Java and the islands of Timor, Lombok, and Sumba.
Fig. 1

General map of Eastern Asia; the Sunda Shelf and Sahul Shelf regions are shaded

North of the equatorial region, the NE and SW monsoons dominate the climate and surface ocean circulation. Rainfall becomes more and more seasonal eastwards and northwards from the equatorial subregion, with typhoons and cyclones (defined as storms with wind speeds exceeding 73 mph) associated particularly with the warm SW monsoon season. Typhoons originating in the Pacific pass through the Philippines before reaching the coastline of Vietnam and southern China. There is a “typhoon belt” from central Vietnam to Hainan Island where most of these typhoons strike land, causing wave surges of up to 2.5 m above normal sea level. Similar storms originating in the Bay of Bengal move northwards and commonly strike the coast of Bangladesh as cyclones. A key consequence of these monsoonal weather phenomena is that the most vulnerable coastal regions of Vietnam and Bangladesh are protected by man-made earthen sea dikes that have transformed the coastal ecology of the upper intertidal zone; these coastal defenses have also served to reclaim land for agriculture, salt-making, and aquaculture.

Further north, the coastlines of China and the Korean Peninsula are influenced by the East China Sea and the Yellow Sea. The latter is a productive, semi-enclosed water body with an average depth of only 44 m and a maximum of 100 m. The Yellow Sea is influenced strongly by several major rivers, especially the Huang He (Yellow River) and Yangtze River, which discharge more than 1.6 billion tonnes of sediments annually. Sedimentation and salinity, as well as seasonal temperature changes, control the ecology and productivity of the Yellow Sea ecosystem. The coastline of China consists mainly of mudflats and salt marshes. There are also large areas of intertidal mudflats and salt marshes along the west coast of the Korean Peninsula that provide an important ecological support function to migratory birds (including the very rare black-faced spoonbill Platelea minor: world population in 1998 only 613), as well as fisheries stocks (Kellerman and Koh 1999).

Coastal Habitats of Eastern Asia

This section describes the ecology of the main coastal habitats founds in Eastern Asia, particularly the mangrove forests, seagrass beds, and coral reefs of Southeast Asia which are the most productive and diverse in the world. However, Eastern Asia is a region where the natural ecology of the coast shows a complete spectrum of impacts due to human activities, from near pristine beaches and coral reefs on remote islands, to massive coastal land conversion for agriculture, aquaculture, and urban/industrial uses. The pressures from human population and development, particularly in heavily populated countries like Bangladesh, China, Indonesia, and Vietnam, have transformed or degraded the coastal zone at an alarming rate over the past 20 years.

Mangroves

Mangroves, or mangrove swamp forests, consist of trees and shrubs growing in the upper intertidal zone of muddy tropical and subtropical shores, including estuaries and lagoons. Mangroves develop best along sheltered shores where there is high and prolonged rainfall and an average temperature exceeding 20 °C (Macnae 1968). Mangrove forests provide important habitat and other ecological support functions for many terrestrial and aquatic animals, including both resident and visiting species, especially birds, as well as fish and shellfish populations that support substantial coastal fisheries (Macintosh 1982). For this reason, it is usual today to regard mangroves as an ecosystem rather than simply a community of highly adapted plants and animals. The biology and ecology of mangroves has been reviewed in detail, notably by Macnae (1968), Tomlinson (1986), Robertson and Alongi (1992), and Hogarth (1998), while their traditional exploitation for forestry, fisheries, and aquaculture production is also well documented. An early account by Watson (1928) and a recent update by Gan (1995) describe the mangroves of Matang in Perak, Malaysia, which have been under management for wood production since the 1900s (mainly for charcoal). Matang is widely regarded as the best-managed mangrove forest ecosystem in the world. Schuster (1952) gives an excellent account of the partial conversion of mangroves in Java to integrated mangrove fishponds, or tambaks, for milkfish culture, with marine shrimps (Penaeidae) and mud crabs (Scylla spp.) being the secondary crop. The current tambak management system in Indonesia is described by Sukardjo (2000). While these represent good examples of the sustainable economic use of mangroves in Eastern Asia, it is really only within the past decade or so that all the functions, attributes, and values of mangroves (and other tropical coastal ecosystems) have become widely recognized and understood (e.g., White and Cruz-Trinidad 1998).

According to the World Mangrove Atlas, 41.5% (75,173 sq. km) of the world’s total mangrove area (181,077 sq. km) are found in South and Southeast Asia. Indonesia (42,550 sq. km of mangroves) dominates with 23% of the world resource (Spalding et al. 1997). Mangroves occur throughout the tropical and subtropical regions of the world, but the Indo-Pacific region is clearly their center of diversity, with 63 out of the 90 or so genera of mangrove and associated plants occurring here. Mangrove forests extend into the colder temperate subregion of Eastern Asia as far as southern China (Hainan Island and Fujian Province), Taiwan, and the Ryukyu Islands of Japan (Fig. 2). The Ryukyus (26–27°N) are the northern limit for mangroves; here temperatures in winter fall to 17–22 °C. At these northern extremes, the mangrove vegetation is much more stunted and limited in species compared to the magnificent mangrove forests of tropical Asia. The drop-off in mangrove species with latitude is shown clearly in China’s Fujian Province. In southern Fujian, there are six mangrove species (Aegiceras corniculatum Avicennia marina, Acanthus ilicifolius, Bruguiera gymnorhiza, Excoecaria agallocha, and Kandelia candel); this falls to four species in central Fujian and to only one species (K. candel) in northern Fujian (Peng and Wei 1983). Further north along the coastline of China, salt marsh vegetation, especially Salicornia, replaces mangrove as the dominant intertidal wetland community.
Fig. 2

Distribution of mangrove swamp forest in Eastern Asia (heavy coastlines)

It is in Southeast Asia where mangroves have achieved their greatest development and diversity, especially along the sheltered shores bordering the shallow seas of the Sunda Shelf within the Malay–Indonesia subregion (Fig. 3). This includes the coasts of Peninsular Malaysia and Sumatra adjoining the Melaka (Malacca) Straits, the Gulf of Thailand and the coast of Cambodia, the Mekong Delta of southern Vietnam, the northern coast of Java, and almost the entire coastline of Borneo (see Fig. 2). The prolific reproductive capacity of the main forest-forming Asian mangrove species is one reason for their great success throughout Southeast Asia (Fig. 4).
Fig. 3

Tall, stilt-rooted Rhizophora trees dominating a typical estuarine mangrove forest in Southeast Asian (Ranong, southern Thailand)

Fig. 4

Spear-like propagules of Rhizophora mucronata adapted for penetrating soft muddy sediments. Propagules give mangrove trees of the Family Rhizophoraceae, great capacity for self-generation and colonization

Under the more exposed conditions of the Bay of Bengal and South China Sea, it is in the great deltas of the Ganges–Brahmaputra (Bangladesh), Irrawaddy (Myanmar), and Red River (northern Vietnam) where mangroves are most extensive and luxuriant. In each case, massive deposition of alluvial sediments from the river systems creates mud banks along the shallow coastal zone that enable mangrove forests to colonize and flourish. At the same time, the presence of mangroves affects the hydrological regime by modifying tidal flows and velocities, influencing sedimentation and erosion patterns, and reducing the impact of waves along the coast (Wolanski and Ridd 1986; Kjerfve 1990). Thus, mangrove systems are highly dynamic, both in the short-term and over longer time periods. The longer-term dynamic changes in coastal land formation resulting from these processes are well illustrated historically, especially in the Sunda Shelf subregion. Palembang was a thriving port city when Marco Polo visited Sumatra in 1292, but since then coastal accretion has left Palembang more than 50 km inland (Macnae 1968).

The rates of “land-building” by mangroves are lower on more exposed coastlines due to less favorable current and/or climatic conditions. Mangroves rapidly colonize the mudbanks formed in the Irrawaddy Delta, but some sediments are carried away eastwards and offshore by coastal currents generated during the monsoons. In the Mekong Delta, there is a net flow of sediments from east to west, and consequently some parts of the eastern shore of the Cam Mau Peninsula are actually eroding, despite the great sediment loads being deposited by the Mekong River system. Moreover, Typhoon Linda, which struck southern Vietnam in November 1997, destroyed the last vestiges of the original mixed forest, as well as damaging many of the older mangrove forest plantations in Ca Mau. As in China, the colder climate in northern Vietnam, coupled with frequent typhoons, limit mangroves in the Red River Delta to low, shrubby vegetation (dominated by Avicennia spp. and K. candel). In contrast, the mangrove forests of southern Vietnam feature taller trees of Rhizophora Sonneratia, Brugueira, and Ceriops spp., including large tracts of plantation mangrove consisting of a single commercial species, Rhizophora apiculata integrated with canals for aquaculture (Fig. 5).
Fig. 5

A dense monoculture of planted R. apiculata trees in Ca Mau, southern Vietnam. Mangrove forestry on the central platform is integrated with aquaculture in the surrounding water canals (foreground).

Nipa Swamp Forest

Along tropical riverbanks, and in low-lying muddy swamplands subjected to greater freshwater inundation, the nipa palm (Nypa fruticans) replaces mangrove forest as the characteristic plant community (Fig. 6). Nipa palms often intergrade with mangroves in estuarine transition zones near the upper limit of saltwater penetration. Large areas of nipa swamp have been destroyed by land reclamation projects and for shrimp farming, but nipa remains an important wetland community in many Southeast Asian countries, both ecologically and economically. Nipa is still used widely in Southeast Asia as a traditional thatching material for house- building; it can also be processed for sugar and alcohol production (Chan and Salleh 1987).
Fig. 6

A dense stand of the palm N. fruticans, at the transition zone from mangroves to freshwater vegetation, Mekong Delta, Vietnam.

Salt Marshes and Mudflats

Salt marshes replace mangroves in the coastal ecology of the temperate subregions of Eastern Asia, especially along the sheltered western coastline of the Korean Peninsula. The southern portion of the Yellow Sea, including the entire west coast of Korea, is dominated by tidal flats up to 10 km wide, with an operating tidal range of 4–10 m. This forms the Yellow Sea ecoregion that includes an estimated 2850 km2 of tidal flats (Kellerman and Koh 1999). Salt marsh vegetation characterized by Suaeda japonica once flourished on the upper part of the shore, but much of this has been lost through land conversion for agriculture.

The tidal flats of the Yellow Sea ecoregion contain muddy, sandy, and mixed sediments; these areas are highly productive, with a rich benthic fauna of polychaetes, bivalve and gastropod mollusks, crustaceans, holothurians, and branchiopods (Koh and Shin 1988). The tidal flats are an extremely important habitat for migratory wading birds on their passage between Indonesia–Australia and Eastern Siberia–Alaska. Ecologically, the coastal habitats of the Yellow Sea have been likened to those in northern Europe, particularly the Wadden Sea (Kellerman and Koh 1999).

Salt marsh plants also replace mangroves locally in more arid conditions, even within tropical Southeast Asia. On dry muddy soils above the mangrove zone, or where coastal dikes and embankments have been constructed, the salt-tolerant creeper Sesuvium portulacastrum often covers such exposed habitats, its fleshy leaves being capable of retaining water even during prolonged droughts. In Vietnam, where virtually all the mangrove zone has been disturbed by sea dike and shrimp pond construction, several other marginal species colonize the supralittoral zone, including the shrubs Clerodendron inerme and Pluchea indica and the tree Thespesia populnea, which produces a hibiscus-like flower. Such high, arid habitats are hostile to most marine animals, but fiddler crabs (Uca spp., Family Ocypodidae) and mangrove sesarmid crabs (Family Grapsidae) burrow deeply into the soil for protection. A few mangrove species, especially E. agallocha and Lumnitzera racemosa also tolerate the dry, acidic conditions on the slopes of coastal dikes. Local farmers in Vietnam often plant these mangrove trees, along with Thespesia and Casuarina, to provide shade and wind protection for their houses and farmland. Very poor people also gather Sesuvium for use as animal fodder.

Sandy Beaches

Eastern Asia includes some of the most magnificent sandy beaches in the world, many of which are still unspoiled, particularly those fringing remote coral islands. The world’s longest beach is located on the Arakan coast (now Rhakine) of Myanmar, while the powdery white beaches of Boracay Island (Western Visayas, the Philippines) are regarded by many to be the world’s finest. Beautiful sandy beaches also make up 90% of the eastern coastline of Peninsular Malaysia. Not surprisingly, the sandy beaches of Indonesia, Malaysia, Philippines, Thailand, and more recently Vietnam, are promoted strongly as a key attraction to tourists. Particularly renowned are the beaches on many tropical islands such as Bali and Lombok (Indonesia), Penang and the Lankawi Islands (Malaysia), Phuket and Koh Samui (Thailand), Boracay (Philippines), and Phu Quoc (Vietnam).

Beach sediments of volcanic origin occur in parts of Indonesia, such as eastern Java, creating beaches of black or gray sand. Beach ridges and sand dunes are not well developed in the humid tropical regions of Asia, but examples occur in parts of southern Java and southwestern Sumatra; here a natural beach ridge and dune vegetation of Casuarina, Pandanus Calophyllum, Inophyllum, and Barringtonia occurs, together with planted or self-established coconut palms. A similar sandy ridge and sand dune formation occurs much more extensively in monsoonal Asia, especially along parts of the coastline of Myanmar and Vietnam. Natural and planted Casuarina equisetifolia trees are a feature of the low sand ridges behind the beach slope. In many provinces of Vietnam planted Casuarina trees act as a wind break in front of coastal villages, as well as providing a traditional, and renewable, source of wood (Fig. 7). The slender form of the branches and leaves of this native conifer enables Casuarina to withstand the arid conditions and strong winds associated with sea-facing sandy beaches.
Fig. 7

Planted C. equisetifolia trees serving to stabilize the upper beach zone and provide a windbreak, Nam Dinh Province, northern Vietnam

Within the upper intertidal zone on exposed shores with strong surf, the sand is too dry and unstable for most marine animals, but burrows of the ghost crab Ocypode ceratophthalma are a common site on the upper beach slope. This large ocypodid crab burrows deeply for protection from the sun and desiccation. Ghost crabs emerge at low tide to scavenge from the sand line, or to chase and capture smaller fiddler crabs (Uca spp.) or soldier crabs (Dotilla spp.) which occupy the lower, less-exposed intertidal zone. As the fastest running land crustacean, Ocypode is particularly well adapted to catch its prey and to escape predators.

Of the seven species of sea turtles found in the world, four species visit sandy beaches in Malaysia to lay their eggs. The beaches of Rantau Abang, in Trengannu on the east coast of Peninsular Malaysia, are one of only four main nesting sites worldwide known for the giant leathery turtle, Dermochelys coriacea, and the only nesting site in Eastern Asia. This rare and endangered species is the world’s largest living reptile, capable of reaching 2 m in length with a weight of more than 900 kg. It is also the only sea turtle without a hard shell; instead it has a leathery, ridged carapace. Although this unique species has a worldwide distribution, being found even in temperate seas, it only breeds in the tropics. After laying many large parchment-like eggs in a nest dug carefully in the sand at the top of the beach slope, the female turtle returns to the sea. As soon as the eggs hatch the baby turtles struggle out of the sand and crawl down the beach slope to enter the sea. Despite efforts to protect its nesting beaches in Malaysia, the giant leathery turtle has declined significantly over the past 30 years, disturbance to its nesting habitat being one of several critical factors.

The other turtles nesting on Malaysia’s beaches are also endangered, having suffered severe decline due to egg harvesting and relentless fishing pressure because of their high value. It is also likely that their feeding habitats have declined significantly. The olive ridley turtle (Lepidochelys olivacea) is the world’s smallest marine turtle; its diet includes crustaceans, mollusks, and jellyfish. The green turtle (Chelonia mydas) has a vegetarian diet of seagrasses and algae, though it may also consume sponges The beautiful hawksbill turtle (Eretmochelys imbricata) also feeds on sponges. The hawksbill and ridley turtles are hunted for their shells, while the green turtle is prized for its meat and oil. The same four species of marine turtle occur in the Philippines (Gomez 1980), but they have declined greatly in numbers, just as in Malaysia, despite conservation measures including closed seasons for turtle fishing and egg-collecting (Palma 1993). Sea turtles are particularly difficult to conserve because of their precise habitat requirements, as well as their high value to poachers. The disturbances to their historical breeding beaches, and the great decline in coral reefs and seagrass beds which provide sea turtles with feeding habitats, place these remarkable marine reptiles at great risk, even if hunting them can be controlled.

Coral Reefs

There are almost 100,000 sq. km of coral reefs in Southeast Asia, representing about one-third of the world’s total coral resource. Like mangroves, corals show their greatest diversity in Southeast Asia, with 600 of the almost 800 reef-building coral species found in this tropical subregion of Eastern Asia. The center of coral diversity is eastern Indonesia, the Philippines, and the Spratly Islands with over 70 genera of hard coral represented. Indonesia and the Philippines, alone contain 77% of the region’s coral reefs due to their multitude of islands featuring the sheltered, clear water conditions corals require. Coral reef fishes, crustaceans, and mollusks also show their greatest diversity in this subregion and up to 3000 animal species may be present on a single coral reef. A recent identification guide to corals of the world (Veron and Stafford-Smith 2000) provides an excellent reference to the corals of Eastern Asia. Several new coral species are described and there are probably many more species still to be identified.

Notwithstanding their great beauty, diversity, and ecological importance, the world’s coral reefs have suffered a dramatic decline in recent years. About 10% may already have been degraded beyond recovery; a further 30% are likely to decline seriously within the next 20 years. Recently, the World Resources Institute estimated the potential threat to coral reefs using standard criteria to calculate a “reefs at risk” indicator (Bryant et al. 1998). The reefs identified as being at greatest risk are in South and Southeast Asia, East Africa, and the Caribbean. Specifically, over 85% of the reefs of Indonesia and Malaysia, and over 90% of those in Cambodia, Singapore, the Philippines, Taiwan, and Vietnam are threatened (Fig. 8).
Fig. 8

A coral reef flat of hard and soft corals in Singapore; heavy coastal industries can be seen in the distance.

Seagrass Beds

Seagrasses are distributed widely through tropical and subtropical Eastern Asia, mainly as low intertidal to subtidal beds in shallow sandy bays, lagoons, and around near shore islands. They often form an associated wetland community below mangrove-fringed shores with sandy sediments, or occur interspersed with coral reefs. Like corals, seagrasses do not tolerate the muddy or turbid habitat conditions typical of estuaries and mudflats. In Vietnam, for example, where more than 5000 ha of seagrass beds containing 15 species have been identified, the main sites for seagrasses are north of the Red River Delta in Quang Ninh Province, in the central region of Vietnam (Hue and Khanh Hoa-Nha Trang) where there are many magnificent sandy bays and lagoons, and around the southern island of Phu Quoc (Vietnam Environmental Monitor 2002). Seagrass beds in Vietnam have become heavily degraded due to excessive harvesting for animal food and organic fertilizer, as well as destructive fishing practices (use of dynamite and cyanide) in seagrass and coral habitats.

Coastal reclamation projects have also caused widespread loss of Eastern Asia’s seagrass beds and coral reefs, but there is also growing evidence of decline due to natural causes, including coral bleaching associated with warming of the seas and “wasting disease” in seagrasses. Haynes et al. (1998) concluded that most seagrass losses, both natural and anthropogenic, stem from reduced light intensity due to sedimentation and/or epiphytic development caused by water nutrient enhancement.

Coastal development activities commonly increase sediment loading in the surrounding waters, causing great harm to seagrass beds and coral reefs. One well-documented example is Hong Kong’s Chep Lap Kok Airport (Lee 1997). Increased sediment levels caused by the airport’s construction virtually wiped out the nearby beds of Zostera japonica and Halophilia ovata. While Halophilia has recovered well following the construction period, the Zostera beds have almost completely disappeared, although some transplanted patches have survived and enlarged. This difference between seagrass species may be explained by the observation that Zostera is mainly subtidal and intolerant of shading, whereas Halophilia also occurs in the lower intertidal zone and can survive in relatively low light intensity.

Seagrass beds play various ecological roles, including sediment adsorption and nutrient absorption from seawater; this may serve an important protection function for adjacent coral reefs, since corals are even more sensitive to sediment and nutrient loading. Seagrasses also provide important nursery habitats for many fish species, including groupers fingerlings, for example, which are heavily collected throughout Southeast Asia for aquaculture. Seagrass beds are also critical feeding areas for the green turtle (C. mydas) and the rare sea mammal, the dugong (Dugong dugun), which feeds almost exclusively and selectively on various seagrasses, especially Halodule and Halophilia. Dugongs may choose these particular grasses in preference to other genera (Thalassia and Enhalus) because they are easily digested (Halophilia) and rich in available nitrogen (Halodule). Dugongs are capable of digesting a large volume (8–15% of body weight per day) of low quality plant material (Reynolds and Odell 1991), an observation that explains why the great loss of seagrass beds in Eastern Asia has been so damaging to the survival prospects for this unique mammal. It has also been reported that grazing by dugongs and turtles plays an ecological role in seagrass communities by stimulating the growth of new leaves, thereby changing the structure and nutritional status of the seagrass bed (Aragones and Marsh 2000).

Exploitation of Coastal Resources

Human Pressure

Eastern Asia is a region where the great natural diversity of coastal topography, biological communities, and species has been transformed in many countries by immense human population and development pressures. Although human occupation and economic use of the coastal zone have a long tradition in the region, dating back centuries in the case of coastal farming and aquaculture, the pace of coastal development has accelerated since the 1980s, raising the need for habitat conservation and integrated coastal zone management as never before.

The effects of high population growth in the coastal zone, unsustainable exploitation of coastal resources, and conversion of coastal habitat for agriculture, aquaculture, and urban and industrial development, have now reached crisis levels. In reviewing the threatened status of wetlands in Asia in 1989, Wetlands International (an international NGO) noted that Southern and Eastern Asia (including the Indian subcontinent) had an average population density about eight times that of the rest of the world and was increasing at a rate of 55 million people annually. This led Wetlands International to conclude that, “Most of the threats to wetlands in Asia are a direct consequence of the need to feed and house this massive and ever-increasing number of human beings.” Unfortunately, this is a very accurate assessment of the problems facing Eastern Asia’s coastal ecosystems in general.

A good historical example is the Chakaria Sundarbans region of Bangladesh. Located on the eastern border of the Bay of Bengal, this is the eastern limit of the great Sunderbans mangrove forest shared between Bangladesh and India and the largest mangrove ecosystem in the world. One hundred years ago the Sundarbans was reserved forest, but over the next several decades the mangroves were exploited for wood and fishery products and then encroachment followed for human settlement and salt production. Mangrove conversion accelerated greatly during the 1980s due to the development of coastal shrimp farming, until by 2001 all the remaining mangrove had been converted to shrimp ponds and human settlements (Hossain and Kwei-Lin 2001). Even by the 1980s, the Chakaria Sundarbans were considered too degraded to merit any special conservation efforts.

There has been a similar history of mangrove exploitation in Vietnam, where now less than 30% of the original mangrove area remains and virtually no pristine forest has survived. Only 60 years ago, mangroves in Vietnam covered an area of up to 400,000 ha (Maraund, 1943 cited by Hong and San 1993), of which about 250,000 ha flourished in the Mekong Delta. The greatest concentration of mangrove (150,000 ha) was in the Minh Hai Peninsula at the southern tip of Vietnam (now divided into Ca Mau and Bac Lieu provinces). The most recent estimate for the total area of mangrove forest remaining in Vietnam is only 110,000 ha (Vietnam Environmental Monitor 2002). Overall, the Eastern Asia region has lost more than 60% of its mangrove forest in just a few decades (Table 1).
Table 1

Estimated loss of the original mangrove forest area in different countries. (Based on data from World Resources Institute 1996)

Country

Loss of mangrove forest (% loss by area)

Bangladesh

73

Brunei

17

Indonesia

45

Malaysia

32

Myanmar

58

Singapore

76

Thailand

87

Vietnam

62

Unweighted average for Asia

61

It is not just Eastern Asia’s fragile tropical mangrove forests, seagrass beds, and coral reefs that have become severely depleted or degraded. Approximately 600 million people live in the area around the Yellow Sea, including major cities such as Shanghai, Seoul-Inchon, and Pyongyang-Nampo. The Yellow Sea is among the most heavily exploited coastal and marine areas of the world, with more than 100 species of fish, crustaceans, and cephalopods captured by its fisheries. Today, coastal habitats and fishery resources in the Yellow Sea are threatened by both land-based and sea-based infrastructures, by pollution, and by overfishing and other forms of unsustainable resource exploitation. More than 100 million tonnes of domestic sewage and about 530 million tonnes of industrial wastewater are discharged annually into the nearshore areas of the Yellow Sea. These discharges come from large coastal cities, shipping, and oil exploration; they contain many pollutants, including heavy metals (cadmium, lead, mercury), oil residues, and nitrogenous compounds.

Other economic uses of the coastal zone in Eastern Asia tend to reflect the stage of development of the countries concerned. Like Bangladesh and Vietnam, the more developed South-east Asian countries of Indonesia, Malaysia, Philippines, and Thailand have heavily exploited sheltered bays, lagoons, estuaries, and other mangrove and mud flat areas for coastal agriculture and aquaculture. There has also been localized industrial and urban development, as well as heavy investment in tourist infrastructure centered on islands and mainland sandy beach sites near major cities; for example, Pattaya and Hua Hin in Thailand, Port Dickson and Johore in Peninsular Malaysia (Fig. 9). Estimates for Thailand made by the Royal Thai Forestry Department in 1993 revealed that, of the original 372,448 ha of mangrove forest (measured in 1961), 133,812 ha (35.9%) had been converted into salt pans, mining, agriculture, and infrastructure, 64,991 ha (17.5%) was occupied by coastal shrimp farms, and 4961 ha (1.35%) had been converted to other uses (leaving only 45% undeveloped).
Fig. 9

Recreational use of a sandy beach in Johore, Pensinsular Malaysia, with dense surrounding urban infrastructure – a scene typical of many beaches near large cities throughout Eastern Asia

In the most populated and developed parts of Asia, especially Hong Kong, Singapore, and parts of Peninsular Malaysia, China, and Korea, coastal land is at such a premium that urban and industrial development (e.g., airports, container ports, oil-refineries) have almost completely replaced earlier natural resources use. Such economic developments have overtaken the coastal zone in a remarkably short period of time. Only 50 years ago Schuster (1952) noted “The greater part of down town Singapore is built on Rhizophora piles driven into the mud of the harbor region.” Today only carefully conserved vestiges of the original coastal habitat remain in Singapore (e.g., Fig. 8).

Coastal Aquaculture

Of the many human uses of the coastal zone, aquaculture stands out not only in terms of its scale and importance throughout the Eastern Asia region, but also because of its interaction with the ecology of the coastal environment (e.g., Primavera 1993). Unlike the conversion of coastal habitat to agriculture or urban and industrial uses, the production of human food by aquaculture is still critically dependent on the carrying capacity of the surrounding aquatic ecosystem. Where coastal aquaculture causes environmental degradation, there is a rapid negative feedback on the viability of the aquaculture production system itself, as the experiences with intensive shrimp farming in Eastern Asia show only too well (e.g., Smith 1999). The term “self-pollution” is sometimes used to describe this problem in coastal aquaculture (Phillips and Macintosh 1997).

Shrimp Farming

Shrimp farming has had a dramatic impact on the coastal ecology of Eastern Asia over the past 20 years or so. Although coastal aquaculture has a long history of operation in Southeast Asia (Schuster 1952; Macintosh 1982), it was the commercialization of technology for breeding one particular species, Penaeus monodon, or the black tiger shrimp in Taiwan, which enabled shrimp seed (post-larvae) to be produced, then reared intensively in coastal shrimp farms. The world demand for farmed shrimp also rose significantly in the 1980s, led at that time by Japan, because the yields from shrimp capture fisheries had long since reached a ceiling level. From early pioneering research on the breeding of Marsupenaeus japonicus in Japan, research then developed in China involving the local species Fenneropenaeus chinensis and in Taiwan with P. monodon. Cool climatic conditions and high costs had mitigated against shrimp farming in Japan involving the local species M. japonicus, but the black tiger shrimp was readily accepted by the Japanese market and Taiwanese shrimp producers rapidly spread their knowledge to other parts of tropical Asia where conditions for farming P. monodon were much better. During the 1980s, investors in Thailand, Philippines, Indonesia, and Malaysia rushed to adopt the new technology, converting mangrove forests, traditional shrimp ponds, salt pans, coastal rice fields, and (in the Philippines) sugar plantations, into intensive shrimp farms. From Southeast Asia, “shrimp fever” as it became known (Primavera 1993) spread to Vietnam and Bangladesh, countries with huge areas of coastal mangroves and mudflats considered more suitable for conversion to extensive, low-cost, shrimp ponds. Since 1995, records show that on average 138 million shrimp juveniles, or “seed” (mainly of P. monodon and Macrobrachium rosenbergii) have been collected annually from the Sundarbans reserve forest in Bangladesh to support coastal shrimp farming. Shrimp seed collecting is extremely destructive as many other species of fish and crustacean seed are caught and discarded by the shrimp fishers, but it is a form of livelihood for the great majority of families living in the Bangladesh Sundarbans and involve an estimated 225,000 shrimp seed collectors (Rouf and Jensen 2001).

Shrimp farming was also promoted on a massive scale in China, with shrimp farms occupying 160,000 ha from Hainan Island in the south to Liaoning Province in the northern temperate zone. Production reached a peak of 200,000 t in 1992 before coastal water pollution and shrimp diseases had a devastating impact on output (Smith 1999). Shrimp farming has also developed in Korea, but as with its neighbors China and Taiwan, aquaculture has been badly affected by coastal industrialization and associated problems of water pollution (including self-pollution) and shrimp disease outbreaks (Fig. 10). The shrimp farms in Korea are confined almost entirely to the west coast where it is more sheltered. The majority of farms are located within the intertidal zone or near to the coastline. Reflecting the colder operating conditions in Korea compared to Southeast Asia, the main species cultured are the local shrimp F. chinensis followed by M. japonicus. Annual production levels are rather low (less than 1 t/ha), but the environmental limitations on shrimp production in Korea are offset by the high price farmers can obtain for live shrimp delivered to the restaurant trade, including live sales to Japan.
Fig. 10

Intense use of the coastal zone for aquaculture; the photograph shows ponds and a complex of water pipes supporting fish and shellfish farming during the aquaculture boom in southern Taiwan in the 1990s

Mud Crab Culture

Poor coastal communities from Bangladesh to the Philippines are still heavily dependent on mangrove-based fisheries and aquaculture to support their livelihoods (Fig. 11). This includes crab fishing for Portunus (blue swimming crab) and Scylla (mud crab), as well as shrimp fisheries and shrimp culture. Mud crab culture has also developed rapidly as a secondary activity to shrimp farming within the mangrove forest ecosystem. It carries much lower investment costs and risks than shrimp farming and is therefore more suitable for poor families (Overton and Macintosh 1997). In the Lower Mekong Delta of Vietnam, farmers can now rear from 500 to 800 kg of mud crab per hectare in a simple mangrove pond (unpublished data). With a farm gate value of about USD3/kg, even a small crab pond can provide a poor Vietnamese family with an annual net income of USD200–300. This is a significant contribution to the economy of families living in remote coastal areas where the potential daily income from fishing, salt production, or agricultural laboring is only USD1–2.
Fig. 11

A large mud crab (Scylla paramamosain) for sale in a local market in Vietnam. Mud crabs support important artisanal fisheries and coastal aquaculture production throughout Eastern Asia

Other Forms of Coastal Aquaculture

Many other types of aquaculture are also economically and ecologically important in the coastal zone of Eastern Asia. Economically, caged fish culture for valuable species such as groupers (Epinephelus spp.) and snappers (Lutjanus spp.) appears to be very attractive, but it carries many risks, especially from fish diseases and can be highly polluting due to the use of trash fish as the main type of feed. The environmental damage stemming from large-scale collection of wild fingerlings (especially groupers) from coral reef and seagrass habitats to support aquaculture is another great cause of concern. For large-scale aquaculture production, and in terms of their ecological impacts, the culture of bivalve mollusks and seaweeds has many advantages over most fish and crustacean species. Mollusks and large seaweeds are cultured in huge quantities by both China and the Republic of Korea. For example, marine aquaculture production in China reached 10.6 million tonnes in 2000, with 93% of this total contributed by bivalve mollusks and seaweeds. The main species of mollusks include oysters (Crassostrea), mussels (Mytilus), hard clams (Meretrix meretrix), short-necked clams (Mactra spp.), scallops (Clamys farreri), and ark shells of the genus Anadara (Fig. 12). Gastropod mollusks of the genus Haliotis, better known as abalone, are more difficult to rear, but are in high demand as a delicacy. These snail-like animals occur naturally on subtidal rocks (especially in Korean waters) where they graze on algae. However, overfishing has decimated abalone populations because they are so valuable and easy for divers to harvest.
Fig. 12

The ark shell, or “blood cockle” (genus Anadara), one of the many bivalve mollusks found abundantly on coastal mudflats throughout Eastern Asia and important in aquaculture, especially in Malaysia and China

Seaweeds grow naturally on rocks in the lower intertidal and subtidal zones, especially in the warmer southerly regions of the Yellow Sea. The seaweed Pelvetia siliquosa occurs widely in the Shandong and Liadong regions of China, as well as around the Korean Peninsula. It grows most luxuriantly in Korean waters where it has been harvested for hundreds of years and exported to China. Sargassum pallidum, another edible seaweed, dominates in the west Yellow Sea, and Plocamium telfairiae is also common there. A cold water seaweed, the kelp Laminaria japonica has become the most important seaweed cultured in China. Introduced from Japan, kelp farming now occupies more than 3000 ha of China’s coastal waters (yielding 10,000 t dry weight/year) and is supported by hatcheries producing young plants for transfer to growing frames in the sea once the water temperature drops below 20 °C.

Coastal Habitat Conservation and Restoration

Given the already very high human population pressure in many Asian countries, it is difficult to be optimistic about the future for coastal habitats and the communities of plants and animals they support. Coral reefs and seagrass beds are particularly sensitive to destructive fishing methods, pollution, and any increased sedimentation caused by coastal construction or other development activities. Even mangrove forests, which are more robust and relatively easy to manage on a sustainable basis by tree replanting, have disappeared at an alarming rate (Table 1).

There are some positive indications that coastal protected areas (e.g., biosphere reserves, nature parks, and sanctuaries) can preserve habitat and protect species biodiversity. In addition, protected areas can play a valuable role in raising public awareness of the need for such conservation efforts (Fig. 13). Habitat restoration, especially of mangroves, is also being supported very actively in several Asian countries. Thousands of hectares of mangrove have already been planted successfully in Bangladesh and in the Red River Delta and Mekong Delta of Vietnam in order to protect the coastal zone from storms, flooding, and erosion, and to accelerate the reclamation of land from the sea. Mangrove planting also leads to a higher diversity of animals and birds, and to improved fisheries production. However, the full ecological impact of mangrove reforestation need careful assessment, both in terms of the plant and animal communities that develop in mangrove plantations and the physical changes that take place in the ecosystem (Macintosh et al. 2002).
Fig. 13

Tourists, long-tailed macaques, and mangrove forest in the Can Gio Biosphere Reserve, near Ho Chi Minh City, Vietnam. The reserve has conservation, sustainable development, education, and research functions

In contrast to mangroves, it is very difficult to restore coral reefs and seagrass beds and most efforts to date have been only experimental in scale, involving, for example, the transplanting of healthy coral fragments or individual coral heads onto a degraded reef (e.g., Clark and Edwards 1995; Rinkevich 2000). For corals and seagrasses, strict conservation of the coastal habitats supporting these delicate plant and animal communities, including protection from pollution, should be the first priority. This is not simply a plea to protect these diverse coastal communities for biological interest; there are sound economic reasons for doing so. White and Cruz-Trinidad (1998), for example, estimated that the sustainable annual benefit from 1 ha of coral reef in the Philippines is in the range USD31,900 to USD113,000, including its fisheries, tourism, coastal protection, and biodiversity values. This suggests that, conservatively, coral reefs are contributing almost USD1 billion annually to the Philippines’ economy, but equally such huge economic benefits will be lost if coral habitat continues to be destroyed.

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© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Ecology and GeneticsUniversity of AarhusAarhusDenmark