Coastal wetland in South China: Degradation trends

ARTICLES Chinese Science Bulletin 2006 Vol. 51 Supp. II 121—128

DOI: 10.1007/s11434-006-9121-z

Coastal wetland in South China: Degradation trends, causes and protection countermeasures HAN Qiuying1,2, HUANG Xiaoping1, SHI Ping1 1 & ZHANG Qiaomin 1. LED, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China; 2. Graduate University of Chinese Academy of Sciences, Beijing 100049, China Correspondence should be addressed to Huang Xiaoping (email: [email protected]) Received February 27, 2006; accepted July 27, 2006

Abstract There are abundant coastal wetlands in South China and their main characters are the tidal flats, mangroves and coral reefs. In this paper, the status quo of coastal wetlands in South China is introduced and their degradation trends in the last decades are analyzed based on the existing literatures and information. Their degradation trends are characterized by reduction of coastal wetlands’ area, pollution of seawater environment, degeneration of ecological environment, sharp decrease of biodiversity in the wetlands and so on. At the same time, the causes resulting in the above-mentioned degradations are discussed, mainly concluding imperfect systems of management and legislation, deficient property and assessment systems of the wetlands, weak consciousness of protecting coastal wetlands, shortage of basic study and backward management level and so on. Some countermeasures are put forward for the sake of a sustainable use of the coastal wetlands of South China, mainly including establishing and perfecting administrative and legal systems for the coastal wetlands, developing the study on assessment of coastal wetland, heightening the consciousness of public participation, and strengthening scientific research and establishment of wetland nature reserves. Keywords: coastal wetlands, degradation trends, causes, countermeasures, South China.

Coastal wetlands mean the coastal lowlands, tidelands and shallow waters under 6 m water deep during low tide, which usually are submerged by the immobile www.scichina.com

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or flowing water body under sea-land alternation process[1]. The coastal wetlands are classified into twelve types: shallow sea water, under tide water plants, coral reef, bedrock coast, intertidal sandy and rocky beach, intertidal mudflat, intertidal salt marsh, seashore salt water lake, mangrove swamp, seashore fresh water lake, estuary water and delta wetland[2]. Coastal wetlands, as important natural landscapes and ecotypes, have abundant natural resources and specific eco-environmental effects. Coastal wetlands widely distribute in China, amounting to 4.87×106 ha[3], including vast tidal flats and estuarine deltas, etc.[4]. With a rapid development of economy in the coastal area of South China, more and more coastal wetlands have been badly interrupted and destroyed due mainly to artificial factors and thus the sharp contradictions between exploitation and protection of the coastal wetlands in South China (CWSC) are coming gradually. Until now, the existing studies on CWSC focused mainly on their status quo ― and characters[5 7]. There are few papers about study on the degradation trends of CWSC. Environmental deterioration and marine resources reduction caused by irrational exploitation of CWSC will restrict the sustainable development of economy and environment in South China. In this paper, the degradation trends of the coastal wetlands and the main causes are analyzed in terms of relevant literature data and some countermeasures and proposals are put forward for the sake of a sustainable use of CWSC. 1 Status quo of coastal wetlands in South China South China, including Guangdong and Hainan provinces, and Guangxi Zhuang Autonomous Region as well as Macao and Hong Kong, is the area with dense population, rapid developing economy, favorable natural conditions and abundant coastal wetlands (Fig. 1 and Table 1). There are the above-mentioned 12 types of wetlands in south China, especially tidal flats, mangroves and coral reefs. Table 1 Province Guangdong Guangxi Hainan Total

Natural condition in South China[8] Land area (×104 km2)

Sea area (×104 km2)

17.79 23.60 3.39 41.39

41.9 12.9 200.0 254.8

Coastline length (km) 3368 1547 1754 6669

1.1 Tidal wetlands The total area of tidal flats in South China is 2839.58 121

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Fig. 1.

Distribution of main coastal wetlands in South China.

km2[7]. In Guangdong Province, the tidal flats mainly lie in its west and the Pearl River Estuary[9]. The coastal wetland of Pearl River Estuary is a silt wetland, extending 100 m towards South China Sea every year[10]. It has a rich biodiversity with 418 species of zooplankton, 515 species of benthos and more than 302 species of main fishes[7]. In Guangxi, there are abundant tidal flats to be exploited and shallow water biological resources with 104 species of zooplankton, 832 species of benthos, more than 500 species of main fishes and more than 30 species of economic fishes[11]. In Hainan Province, the tidal flats mainly distribute in the front edge of river deltas with plentiful terrigenous detritus. There are 1140 species of organism in the intertidal zone[6].

arbor mangroves, frutex mangroves, arbor half mangroves and frutex half mangroves [5]. There are 11 true species of mangroves and 7 species of semi-mangroves in Guangxi1), mainly Comm. Aegiceras comiculatum, Comm. Avicennia marina, Comm. Kandelia candel + Aegiceras comicutum, Comm. Avicennia marina + Aegiceras corniculatum[12]. There are totally 97 species of phytoplankton, 26 species of zooplankton, 159 species of mutation benthic diatoms, 262 species of macrobenthos, 42 species of fishes, 133 species of hexapods and 128 species of birds in Guangxi[13]. Hainan has 25 species of true mangroves and 10 species of semi-mangroves1). The mangrove region of Hainan is rich in biodiversity, and only in Dongzhaigang there are 78 species of birds belonging to 26 families and 12 genera[14].

1.2 Mangrove wetlands

1.3 Coral reef wetlands

Mangroves distribute intermittently in the embayed coasts and estuaries protected by waves in South China. There are 13 species of true mangroves and 6 species of semi-mangroves in Guangdong1), mainly in four types:

Odd pieces of coastal fringing reefs consisting mainly of reef-building corals communities distribute discontinuously in the coastal waters of South China. There are 110 species of corals in Hainan and total 45

1) Guangxi Mangrove Research Center. A national report about the mangrove in China for the project of reversing environmental degradation trends in the South China Sea and Gulf of Thailand (in Chinese), 2003. 1－9.

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ARTICLES species in Guangdong and Guangxi[15], mainly distributing in the western coasts of Xuwen in Guangdong[16], the western, eastern and southern sea areas of Weizhou Island in Guangxi[17], the sea area of Sanya and Dazhou Island in Hainan[18]. Scattered and small atolls mostly distribute in the islands in South China Sea. 2 Degradation trends of coastal wetlands in South China The degradation of wetlands is an important part of the degradation of the natural ecosystems. That is characterized by imbalances of ecosystem structure and energy flow, the fragmentation of landscapes and the function decline of wetlands induced by nature and human disturbances, and a reduction of the wetland area and biodiversity as well as the deterioration of ecological environment in the macroscopic view[19]. At present, the factors of water environment, soil, and biodiversity in the wetlands are adopted by many researchers as reference standards for evaluation of degradation trends of the wetlands[20]. In this paper, the area, seawater environment, ecological environment and biodiversity of the wetlands are used to evaluate the degradation conditions of CWSC. 2.1 Reduction of wetland area Over-reclamation and irrational exploitation and utilization of the wetlands result in remarkable reduction of the coastal wetlands area in the past decades. The tidal flats were reclaimed and reformed to plant rice and sugarcane from 1950s to 1970s, to develop real estate and urbanization in 1980s, to construct roads, airports, jetties and breeding grounds in 1990s, all these seriously destroy the wetland resources of South China[21]. In the past five decades, the total area of reclaimed tidal flats amounted to 7×105 ha in South China[15], amounting to about 1.79×105 ha in Guangdong from 1949 to 1997, 1.48×105 ha from 1949 to 1989, annually averaging up to 3700 ha, and 3.17×104 Table 2 Data origin Survey in 1950s Coastal forest survey in 1980s Zhang Qiaomin et al. in 1997 State Forestry Administration of the People’s Republic of China in 2002

ha from 1990 to1997, annually averaging up to 4300 ha. But the utilization rate of the reclaimed tidal flats was only about 60% before 1990[9]. The tidal flats in the Pearl River Delta were even seriously destroyed (Fig. 2). The sharp decline in the area of CWSC has resulted in loss and fragmentation of natural habitats and decrease of resource biomass. At the same time, it upset the ways of material cycles and energy flow in coastal wetlands.

Fig. 2. Variation of tidal flat area and inning area in the Pear River Estuary during 1970s—1990s[22] .

In recent decades, mangroves, as an important constituent of the ecosystems of the costal wetlands, are critically destroyed and the resources are gradually decreased. The mangrove area in CWSC was reduced from 41281 ha in 1950s to 14303 ha in 1990s (Table 2)[23]. It should be noticed here that although the mangroves’ area in 2001 was 7413 ha more than that in 1997 as listed in Table 2, but it does not mean that the real area of mangroves in South China increased evidently in a short time, it may attribute to different measure methods used in 1997 and 20021). It is true that the mangroves in South China decreased obviously in the past five decades. In Dongzhaigang of Hainan, as the central distribution zones of the mangroves of CWSC, its 49% of mangroves is almost completely destroyed by the reclamation[23]. The mangroves in Zhanjiang, Xuwen and Pearl River Estuary in Guangdong are badly degraded[24].

Variation of mangrove area in South China (ha)2),[23] Hainan Guangxi 9992 10000 4800 8014 4836 5654 3930

8375

Guangdong 21289 8053 3813 9411

Total 41281 20867 14303 21716

1) See the footnote on page 122. 2) Management Department of Forest Researches in State Forestry Administration of the People’s Republic China. Investigation Report on Mangrove Research in China (in Chinese), 2002.

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ARTICLES The reduction of mangrove area will affect the material cycles, energy flow and biodiversity in the coastal wetlands in South China. Mangroves possess more N and P levels in their nutrient cycles, can absorb certain harmful elements in the sewages, such as Hg, Cd and As, and can enrich heavy metals in the soil beneath them, thus purifying the polluted seawater[25]. Mangrove wetlands possess rich biodiversity. If the mangroves are once destroyed, many species within the wetlands will be extinct[25]. 2.2 Pollution of seawater environment Pollution, one of the worst problems to CWSC, has seriously affected the material cycles of the ecosystem and bio-resource in CWSC by the enrichment action of food chains. Artificial wastes cause pollution of CWSC, such as domestic sewage from cities, fertilizer and pesticides used in agriculture, irrational disposal of industrial wastes and wastes of tourist industry. Inshore pollution in South China mainly occurs in the Pearl River Estuary, Shantou, Zhanjiang, Beihai and Qinzhou[26]. The Pearl River Delta bears 64% of industrial pollutants and 74% of municipal sewage of Guangdong[27]. About 1.8×108 tons of sewage was annually discharged into the Pearl River Estuary in recent years[28]. 2.483×106 tons of pollutants from the Pearl River were discharged into the South China Sea in 2004, amounting to 2.291×106 tons of COD, 5.4×104 tons of phosphate, 6.6×104 tons of ammonia-nitrogen, 9000 tons of heavy metal, 3000 tons of As and 6×104 tons of petroleum[27]. The offshore seawater quality in Shenzhen, Zhuhai and Zhanjiang exceeded the fourth class seawater quality standard of China in 2000[29]. The ecological structure of aquaculture itself and its shortage of breeding mode result in many environmental problems, such as discharge of breeding forages and the used chemical medication[30], which aggravates organic pollution, eutrophication, rapid reproduction of deleterious algae and pathogenic microorganism[31]. The area and output of aquaculture in Guangdong were respectively 3.8 times and 17 times in 2000 as much as those in 1986, but the fed forage amounted to 3 times in 2000 as much as that in 1990[31]. The partial forage remains and excretions deposits led to local eutrophication in the culturing seawater[29]. A large quantity of contaminants produced by aquaculture have polluted CWSC, resulting in death of wetland organisms, destruction of the intrinsic ecological community structure, certain effect on the survival of other species because 124

of enrichment of food chain and damage of the ecological balance in CWSC[31]. 2.3 Eco-environmental degeneration Irrational exploitation in a large scale disturbs, even destroys the ecological structures and functions of coastal wetlands with special ecological value, and induces the environmental degradation of coastal wetlands. Large-scale reclamation work produces certain effects on the wetlands, such as occupation of tidelands, change of dynamic characteristic of tidal currents, deposit of sands and sludge, and variation of the transportation regularity of contaminants, as well as remarkable decline of natural habitats, spawning and breeding grounds of aquatic animals, and thus reducing communities and numbers of the species in the wetlands and a long-term influence on marine biological resources. At the same time, improper alteration and use after inning result in channels blocking and coastal eroding, and influence the drainage of floodwater. Felling mangroves and destroying coral reefs have made CWSC face a series of hazards and disasters, including wind erosion and sandification, erosion and salinization of soil and great changes of habitats. For example, a serious soil salinization occurred in 2000 ha of mangroves in Huiwen of Hainan in the past, as a result of sea reclamation and baldly felling mangroves for cultivation in 1970s[32]. With plentiful mangroves to be felled, 60%—90% of the natural animals with economic value have been lost in the tidal flats of Guangxi[12]. A series of problems have gradually emerged, including evident decline of inshore resources of the fish larvae, coastal erosion and high sedimentary ratio in harbors, serious economic loss resulting from typhoon and storm tide, more unused reclaimed coasts and plain coastal scenery and so on[12]. Coral reef ecosystems are badly destroyed because of port construction, sea reclamation, over-capture of fishery resources, rapid development of tourist industry, and a lot of contaminants produced by rapid development of the coastal industry and agriculture, disturbing the feeding, growth and reproduction of corals, and change of the physical character of seawater due to the scouring of fresh water from the land. The breakage rate of coral reefs in the seacoast of Hainan has reached 80% since 1950s[33], which has led to the erosion and retraction of the coasts, decline of aquiculture resources and deterioration of ecological environment[33].


ARTICLES 2.4 Biodiversity decline The irrational exploitation results in the change and degradation of living environment of organisms in CWSC and makes more and more species, especially valuable and rare species, lose their natural habitats and become endangered or even extinct. It reduces biodiversity, weakens the self-adjusting ability to ecosystems and lowers the stability and orderliness of ecosystems. The biodiversity and biomass have declined very obviously in water area of tidal flats in the Pearl River Estuary in the past twenty years. The species of phytoplankton fell from 158 to 97 and their biomass fell from 1711×104 to 100×104 ind/m3 in winter. The biomass of zooplankton fell from 233.9 to 69 mg/m3 in summer. The reduction of species in the intertidal zones was so obvious that the average biomass dropped from 1207 to 370 g/m2 and the average dwelling density dropped from 887.35 to 84.78 ind/m2. The average dwelling density of benthos dropped from 342 to 153.33 ind/m2[10]. The species of mangroves dropped from 37 in 1988[34] to 27 in 1999 in Hainan[6], which might be attributed to the different classification standards in the surveys. The density of terrestrial birds in the mangroves in Shenzhen of Guangdong was lost by 39% from 1993 to 1998[35]. All these badly threaten the maintenance and development of mangrove ecosystem[35]. Some species of mangroves have gradually disappeared in some areas of Guangxi, for example, Rhizophora stylosa was extinct in Qinzhou and Fangchenggang and Ceriops tagal disappeared in the whole seacoast of Guangxi[36]. There were 81 species of reef-building coral in Luhuitou of Sanya of Hainan, of which, 30 species have been dead[37]. The marine living resources obviously fell and some coral reef organisms with high economic value, such as lobster, sea cucumber, hippocampi, pearl oyster, are seldom to be seen[37]. In Weizhou Island of Guangxi, the coral species dropped from 21 families and 45 genera in 1987 to19 families, 17 genera and 8 uncertain genera in 1998, and to 14 families, 16 genera and 4 uncertain genera in 2001[38]. Faviidae, Poritidae and Acroporidae were the dominant species in Luhuitou of Sanya in 1996[39], but only Acroporidae was absolutely dominant species in 2004[40]. The blind introduction of exotic species destroys and threatens the biodiversity of CWSC. The exotic species endangering the mangroves in South China mainly include Mikania micrantha[41], Sonneratia apetala[42], www.scichina.com


Water Hyacinth and Spartina[43]. Mikania micrantha, a sprawling vine of the family compositae originated in South and Central America, was carried into littoral areas of Guangdong in China by the end of 1980s. It mainly harms special forest, such as natural secondary forest, landscape forest, headwaters protection forest and economic forest. Mikania Micrantha has endangered 3000 ha of forests and made 243 ha of forests die out in Shenzhen[41] and also produced a serious harm in Neilingding Island of Pearl River Estuary. Sonneratia apetala, originally introduced into arboretums from Bangladesh by adding biodiversity, overgrew in the mangroves reserve areas in Shenzhen and Zhanjiang after it was tentatively planted[42]. 3 Causes of CWSC degradation Besides natural and social factors, such as global warming and typhoon storm, rapid population growth and sharp increasing demand on resources, there are the following main causes resulting in the degradation of CWSC. 3.1 Imperfect legal and administrative systems Although China has established a legal framework relating to coastal wetlands, such as “Land Management Law”, “Agriculture Law”, “Marine Environmental Protection Law of the People’s Republic of China”, “Water Pollution Prevention and Control Law”, “Wild Animal Protection Law”, “Notification about Reinforcing Wetland Protection and Management of State Council Office” and “Action Plan on Wetland Protection of China”, there is no special law on protection of the coastal wetlands and the current articles about the protection of the coastal wetlands in the correlative rules and law are relatively scattered. In addition, several administrative departments, such as Ministry of Agriculture, Ministry of Water Resources, Ministry of Land and Resources, State Forestry Administration, State Environmental Protection Administration, State Oceanic Administration and interrelated local administrations are all responsible for the administration of the coastal wetlands, and this confusion of administrative responsibility and a shortage of a coordination system for wetland administration must give a serious effect on the use and protection of the coastal wetland. 3.2 Unsound property right and appraisal mechanisms At present, China’s economic development is in a 125

ARTICLES transforming stage from traditional under-developed extensive model to sustainable developing model and the property right of the coastal wetlands is ambiguous in China. The confusion of the relation of property right leads to ascription pluralistic ownership of property and over-exploitation of CWSC. The coastal wetlands belong to the state, individual and collectivity only have usufruct in China. But the actual property right is divorced from the nominal property right and the main bodies with different interests rob usually the resources of CWSC to get their own interests. In addition, the ecological, economic and social values of the coastal wetlands are usually qualitatively not quantitatively evaluated because of lack systematic study on it. The value of coastal wetlands is difficult to embody in the market under the imperfect market economy in China. 3.3 Weak consciousness for protection of coastal wetlands The unilateral concept of development and human’s centralism are important reasons resulting in the deterioration of CWSC. Human’s centralism neglects the fact that the nature is the precondition for the subsistence and development of humanity. The unilateral concept of development takes the economic index as a criterion of development of society and nation and neglects the environmental protection and control. Many current issues of ecology and environment are attributed to the unilateral and wrong concept. And the problems of CWSC are also caused by the false conception about the coastal wetlands and the ecological function and value of CWSC are not rightly recognized. The public sacrifices environment for the sake of the current economic development under the traditional and unilateral concept of economic development. 3.4 Lacking foundational research and backward science and technology A series of important projects to study CWSC have been carried out now, including “Effect of gulf pollution on mangroves and environmental purification effect of mangroves”, “Biological geomorphological process of coral reefs and their response to the environmental change” supported by the National Natural Science Foundation of China and “Reversing environmental degradation trends in South China Sea and Gulf of Thailand” supported by United Nations Environment Program/ Global Environment Fund (UNEP/GEF). But 126

there are shortages of systematic and thoroughgoing studies on the relationship between scenery pattern and ecological process of CWSC, bidirectional succession of coastal wetland ecosystems and restoration mechanism of impacted costal wetland ecosystems as well as backward technical methods managing and protecting CWSC. 4 Countermeasures for sustainable use of the coastal wetlands The rapid development of economy in South China will aggravate the contradiction between protection and exploitation of CWSC. It is important for the development of economy and society in South China to deal with the relation between protection and exploitation of CWSC. It is necessary to carry out the administrative tactics, namely putting protection of the coastal wetlands first and then their moderate exploitation in order to facilitate the sustainable development of the economy and society in South China. 4.1 Establishing perfect administrative and legal systems of the coastal wetlands It is necessary to forbid blind exploitation and destruction of the coastal wetlands, to transform the extensive developing model into intensive model, and to change the tendency of paying great attention to the productive function of the coastal wetlands but neglecting its ecological function. The special laws on protection and exploitation of the coastal wetlands should be established as soon as possible. The jurisdictions of administrative departments of ocean, fishery, agriculture, forestry and environmental protection should be legally nailed down in order to avoid the confusion of administration. It is also necessary to strengthen organization construction, establish leadership organizations responsible for the protection of coastal wetlands, define the function of each authority and intensify the relationship and coordination between administrative departments in order to realize efficient management and sustainable utilization of the coastal wetlands. 4.2 Developing research of coastal wetland assessment A comprehensive evaluation on the function and benefit of the coastal wetlands is not only the important means for assessing the effects resulted by exploiting the coastal wetlands, but also the scientific bases for


ARTICLES managing the coastal wetlands and stipulating the policy relating to coastal wetlands. It is necessary to carry out a systematic survey on the distribution, current exploitation status and existing issues of CWSC, and establish an information system of coastal wetland resources in South China, sum up experiences and lessons, forecast benefits from the exploitation of the coastal wetlands, make economic analysis on the development of wetland resources and administrate and use the coastal wetlands by joint instructions of economy and administration. 4.3 Strengthening the consciousness of public participation and reinforcing the scientific research At present, a few people participate actively in the environmental protection in China. Many people think the environmental protection and economic development are conflicting. The “Law on Sea Area Use and Management of the People’s Republic of China” and “Law on Marine Environmental Protection of the People’s Republic of China” should be emphatically propagandized. In addition, the governments should lead and educate the public to scientifically exploit and protect the wetland resources for long-term interests and resource reservation of descendants. The scientists should master the updated academic trends, sum up and spread successful experience on the protection, development and utilization of the wetlands, establish an international exchange system, enlarge the international cooperation and develop comprehensive studies. 4.4 Intensifying the natural reserves construction of coastal wetlands There have been 8 national and 14 provincial natural reserves of the coastal wetlands in South China, of which 5 have been in the list of international important wetlands of “the Convention on Wetlands”. But they cannot represent the diversity of the coastal wetland of South China. It is necessary to establish a batch of wetland reserves and special marine reserves being representatives for all kinds of coastal wetlands. The government should stipulate the establishing program of the coastal wetland reserves on the basis of analyzing the current status of the protection of CWSC, set up the coastal wetland reserves system with rational overall arrangement, complete genre, clear structure, prominent keys and moderate wetland area to be covered. Acknowledgements

This work was supported by the In-

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novative Engineering Project of Chinese Academy of Sciences (Grant No. KSCZ2-SW-132), and United Nations Environment Program/Global Environment Fund (UNEP/GEF) (Grant No. UNEP/GEF/SCS/Chi/MoU2c).

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