Mangrove plants produce about one kilo of litter (mainly leaves, twigs, bark, fruit and flowers) per square meter per year. Some of this is consumed by crabs, but most must be broken down before the nutrients become available to other animals. That is where the bacteria, along with fungi, come in. Dividing sometimes every few minutes, they feast on the litter, increasing its food value by reducing unusable carbohydrates and increasing the amount of protein. Fish and prawns then eat partly decomposed leaf particles, loaded with colonies of protein-rich microorganisms.
Mangroves and mangrove ecosystems used to be regarded as "wastelands" of little of no value and were put to a variety of uses such as fish ponds, salt beds, rice fields, urbanization, housing estates, human settlement, roads, mining and similar uses for the so-called "development", which at times resulted in the complete destruction of the whole ecosystem. The local Thailand people have traditionally utilized mangrove forests for a variety of purposes (Table 1).
Tangible or direct benefits from mangrove ecosystem:
1)lumber or construction wood
2)poles, fishing gear, etc.
3)raw materials for the wood-based industry of various nature and charcoal
products
4)non-timber products including tannin to simply raw material for leather
tanning industries and raw materials for indigenous medicine
5)edible products including honey and wax, meat, and drinks and sugar.
Intangible or indirect benefits from mangrove ecosystem:
1)natural spawning ground for fish and crustaceans
2)contribution to mud flat formation and control of erosion
3)capability to check inland salinity intrusion
4)enhanced capability to combat the impact of cyclone and tidal surge
5)enhanced capability to function as a shelter belt during storms and
cyclones.
“XI WORLD FORESTRY CONGRESSION”. <http://193.43.36.7/waicent/faoinfo/forestry/wforcong/publi/v6/>
The mangrove ecosystem in Thailand occupies some 35% of the country’s coastline, covering a total area of 1,964 square kilometers. Most of the mangrove formations are found in the eastern coast of the Gulf of Thailand and in the eastern and western coasts of South Thailand. In Thailand, mangrove ecosystems declined from 3,127 square kilometers in 1975 to 1,964 square kilometers, representing a 2% annual decrease ("Mangroves and their characteristics"). The major factors that caused mangrove degradation are population expansion, higher short-term benefits, lack of government attention and overall awareness, obscure regulations, inefficient reforestation techniques, and inadequate manpower. The destruction of mangrove forests in Thailand for the expansion of tiger prawn culture has also become a very serious problem for mangrove management. The government tried to stop the illegal expansion of prawn ponds, but with little success because of the high price and demand for the product.
Before start of any prawn ponds, there were other uses of mangroves. Starting hundreds of years before commercial shrimp farming began, mangrove areas were cleared for timber, mining, charcoal, agriculture, harbor development and human settlements. The clearing the mangrove forests were due to misconception. During the late 1970’s and early 1980’s when commercial shrimp farming began, the mangrove ecosystem was still not clearly understood (ZB Industries, "Contessa"). Therefore, some governments allowed the conversion of mangrove areas into shrimp farms—primarily for socioeconomic reasons. The shrimp farmers soon found out that these mangrove areas were not suitable for sustainable shrimp farming. Mangrove areas contain acid sulfate soil, which is unfavorable to the requirements of sustainable shrimp farming. The drainage of pond results in exposure and oxidation of sulfate soil, causing excessive amount of sulfuric acid to be released, further jeopardizing sustainability. Furthermore, conversion of mangroves into shrimp farms is cost-prohibitive. Significant capital expenditures are needed for land improvements. Sustainable shrimp farming is the practice of supporting, managing and protecting shrimp cultivation over the long term—not just for the moment.
Coastal areas of Thailand have several conditions that are very favorable to shrimp culture. Typhoons or cyclones seldom affect Thailand. Water temperatures are ideal with small seasonal variations. Furthermore, soils and terrain are often ideal for pond construction. These unique features give Thailand advantages over some other countries in Southeast Asia. Thailand’s shrimp production comes from two principal sources, ocean capture fishery and culture in ponds. In the past, ocean capture contributed the greatest share. . The two most important shrimp fishing grounds in Thailand are the Gulf of Thailand and the Andaman Sea. Today, production from pond culture has exceeded the capture production. Shrimp culture development during the past decade, however, has raised a major concern over mangrove destruction since a large portion of shrimp culture ponds was situated in areas which used to be mangrove.
The objective is to achieve a balance between shrimp farming and the existing ecosystem, an approach that realizes shrimp farming and the environment must and can work together. Large numbers of intensive shrimp farms have achieved remarkable production rates in the first year or so followed by steady or catastrophic decline, and in some case abandonment. However, well managed intensive farms have managed to achieve long term sustained production of 5t/ha/crop, corresponding to farm gate revenue of around $80,000/ha/yr and export value of over $112,000/ha/yr (http://www.agri-aqua.ait.ac.th/). Most governments have realized how necessary mangroves really are to the overall environment. That’s why they have adopted mangrove restoration and conservation programs and have enacted strict legislation to protect mangroves.
The ecological, environmental and socioeconomic importance of mangrove forests is now widely accepted by international agencies, governments, NGO’s, scientists and tropical coastal communities alike. It is appreciated that mangrove ecosystems provide a unique and valuable range of resources and services, making them far more valuable than the sum of the products they generate. Nonetheless, responsibility for mangrove management historically has generally been assigned to sectorial institutions, normally Forestry Departments or their Fisheries counterparts, or in urban settings, to infrastructure or utility authorities.
Most of the work on mangroves has focused mainly on their physical and technical aspects. The social aspect of mangrove restoration had not become an important issue until the people spoke. The social needs of the people who live in and around mangroves or within a reasonable proximity of the mangroves are important issues. The major factors that influence the social needs are:
Salt-water intrusion is another problem that can destroy coastal rice crops. The environmental and economic limitations of coastal rice farming have been overcome by alternately rearing shrimp with a rice crop in the same field, or by converting completely to shrimp farming (Menasveta, Piamsak. Mangrove Destruction and Shrimp Culture Systems). For economic reasons associated with the high price of shrimp, such partial or complete switches from rice farming to aquaculture are putting further pressure on the remaining mangroves.
Although tropical shrimp farming has a long history, dating back at least 400 years, expansion of the industry over the last 15 years has been extremely rapid and it’s environmental impact is now the subject of grave concern. With an estimated 80% of cultured shrimp being sold on global rather than domestic markets this is a valuable source of foreign exchange for developing countries. It is not surprising therefore, that there has been a large increase in the number of countries which are now engaged in shrimp farming. Production trends suggest that the exponential growth period in shrimp culture that occurred during the late 1980’s is drawing to a close, and that expansion looks set to continue, but at a slower rate.
Even with the decrease in the exponential growth, the problem remains serious however; Thailand has lost a total of 203,000 ha, or 52% of the total mangrove resource, since 1961 (http://www.agri-aqua.ait.ac.th/mangroves/). The Thai government has at last recognized the importance of preserving it’s pristine forests and is now using remote sensing to track their loss and to provide a methodology for a cost-effective, reliable and effective information gathering system for sensible mangrove planning and management (http://www.agri-aqua.ait.ac.th/mangroves/). However, despite legislation, there has so far been no firm enforcement and the conversion of mangroves to shrimp farms continues.
Saenger et al. (1983) attributes the general cause of mangrove destruction and degradation to the preference for short-term exploitation for immediate economic benefit, rather than longer-term, sustainable exploitation. In volume terms, timber production from mangrove forests has been minor in comparison to that from other forest types, primarily due to timbers of superior quality being available in tropical inland forests (D.Macintosh and S. Zisman, "The Status of Mangrove Ecosystems"). However on a local scale, mangrove timber has always been important to traditional coastal communities for house and boat building. By far the greatest use of mangrove wood is for fuel, especially charcoal because of the exceptional slow-burning properties of the wood. Due to all the special physical features that mangroves have to offer, mangrove ecosystem is lost at a great rate.
In addition to the physical loss of mangroves through coastal industrialization, there are also concerns over environmental effects from pollution. Whilst semi-intensive shrimp farming may be less detrimental to the environment than other systems of shrimp production, there is still some doubt about its long-term sustainability. They still require large amounts of clean, nutrient-rich water, fish and cereals for feed and wild shrimp fry and/or broodstock from healthy mangroves. The great majority of shrimp farms are throughput systems that are resources are pumped in, used up, and pumped out in a linear fashion, rather than being recycled. The result of this is accumulation of wastes in the surrounding ecosystems, which can lead to severe problems. The continuing high resource demands of such systems makes them unsustainable in the long-term. There was a need for a new system to sustain mangrove ecosystems.
Thailand’s shrimp farming industry’s environmental problems have significantly lowered production. In addition to being beset by various macroeconomic trends, a shortage of shrimp fry and an outbreak of whitespot disease in the last two years helps to explain the decrease in shrimp exports in the past year (1996). It continues to be in many Thai shrimp farmer’s short-term economic interest to abandon declining or failed shrimp farms and relocate into new areas than to reclaim polluted or otherwise damaged ponds. The increase in shrimp exports from countries with lower production costs indicate that it may be in Thailand’s overall interest to reconsider its commitment to shrimp farming, at least on the scale it is currently being practiced (Earth Summit Watch).
In 1996, three tough political developments shook the Thai shrimp industry’s faith in its ability to increase shrimp exports. One, the US shrimp embargo threatened Thailand’s ocean-caught shrimp exports. About 10 percent of Thailand’s shrimp industry currently come from ocean trawling. Two, the European Union has decided to drop Thailand from the list of countries receiving lower tariffs on shrimp imports under the EU’s Generalized System of Preferences. Three, the Japanese government declared that it will insist on higher quality standards for shrimp imports.
The US shrimp embargo was initiated May 1, 1996 by the Court of International Trade in New York. The ruling banned imports of shrimp from trawlers that do not employ the use of Turtle-Excluder Devices (TEDs). The court case was the result of a claim brought by the environmental organization Earth Island Institute arguing that the environmental policies of the US requiring TEDs on domestic shrimp vessels was unfair discrimination because foreign trawlers exporting to the US need not comply with the regulation. The Court of International Trade issued its final ruling on October 1996, following up the preliminary injunction it granted in May. In addition to challenging the ban, Thai officials moved quickly to equip their shrimp fishermen to comply with US standards. Few months later, US agreed to lift the ban on Thai ocean-caught shrimp and certify that Thailand’s attempts at saving the sea turtles were comparable to those imposed in the US.
The European Union increased tariffs on Thailand’s shrimp exports. The European Union has decided to no longer allow Thailand shrimp industry to benefit from the EU’s Generalized System of Preferences (GSP). The GSP allows for reduced tariffs for countries with weak economies and a history of below average economic growth. Thailand no longer qualifies because it is the world’s largest exporter of shrimp and has experienced phenomenal growth in the last fifteen years.
Japan is the leading importer of Thai shrimp; the Japanese economy has been declining. The Japanese has also been looking to countries with lower production costs for its imported shrimp. With other countries like, Vietnam, Malaysia, Indonesia, India, and Bangladesh, producing "better" quality shrimps for less price, the Thailand’s export of shrimps decrease dramatically (Earth Summit Watch).
Thailand started off with extensive shrimp culture systems until the mid-eighties when intensive culture practices were introduced. Beginning with the extensive about three decades ago, parts of this system were modified into a semi-intensive form in 1980, and later the intensive type was introduced in 1987. Nearly all of the extensive farm operators subsequently converted to intensive culture systems. Eighty-five percent of shrimp culture areas employ the intensive culture system, while the rest use the extensive and semi-intensive systems (http:// www.agri.aqua.ait.ac.th/). In considering the historical developments and the physical requirements of the three shrimp culture systems together with the rate of mangrove destruction, it is clear that both extensive and semi-intensive shrimp culture systems resulted in higher rates of mangrove destruction.
The extensive culture system evolved from hunting and gathering of food by coastal communities. The idea arose to use parts of the mangrove as aquatic livestock containment and storage areas during the stormy months when they could not fish at sea in Thailand (http://www.agri-aqua.ait.ac.th/mangroves/). The mangrove was modified into large trapping ponds for small fish and shrimps. Shrimp ponds were comparatively large, ranging from 5 to 10 ha each with peripheral canal around the inner dike. Shrimp seed entrained by the influent water grew in the ponds for 2 to 3 months before the ponds were drained and the shrimps, usually of small size, were harvested. Shrimp production by this extensive method was rather low (http:// www.agri-aqua.ait.ac.th/). Mangrove areas in estuaries have been prime candidates for such pond construction since they typically have gentle slopes, adequate tidal range, abundant wild shrimp seed, and land ownership vested with the government. Such land was usually easy to use and inexpensive.
Developments towards a monoculture of shrimp included the active harvesting of juvenile shrimp from the wild for stocking into culture ponds. The semi-intensive system was introduced into Thailand through the Aquaculture Development Project. Semi-intensive culture ponds may be created through intensification of existing extensive ponds. This may include such things as clearing and leveling the pond bottom.
Some shrimp culturists began developing advanced technologies for intensive culture systems. With these new technologies, the shrimp production rate increased to 6.0-10.0 MT/ha/crop (http://www.zbindustries.com/mangrove.html). Intensive shrimp farming in mangrove areas are sustainable environmentally and economically, only if it is done in the right place, with the right infrastructure, and the right management. Many of the smaller and medium sized shrimp farms have developed in a haphazard manner with no infrastructure in terms of water supply or effluent disposal. Influent and effluent from different farms has become mixed, water quality has declined and disease incidence has increased and spread. Such farms are not sustainable, and are a danger to other well managed farms.
The ground water extracted and used by shrimp cultivation often leaves behind a highly-salinated soil. Living mangrove trees can be affected adversely by the high salinization rates caused by shrimp ponds. This leads to poor water quality in terms of potable reserves as well as irrigation water quality reduction for nearby farmlands. The Thai government and non-governmental organizations such as the Thailand Environmental Institute encourage the construction of shrimp cultivation ponds on salt flats to help alleviate this problem (http://193.43.36.7/waicent/fainfo/forestry/wforcong/publi/v6/). Intensive shrimp farmers avoid much of this problem through the recirculation of their water flow, but this also makes the farms more susceptible to outbreaks of disease.
The farmers have learned that the mangrove area is not suitable for shrimp farm construction because it costs high investment, has poor soil quality from acid sulfate soil, and accumulation of hydrogen sulfide and ammonia in the pond water (Pawaputanon, Oopatham). Shrimp farming then began the trend toward the utilization of the land behind mangrove. Together with new technologies such as formulated feed, water quality management, disease control, and other technologies, shrimp culture has come to more efficient production of more shrimp in less area.
Mangroves in Thailand are sources of timber and non-timber forest products as well as several non-forestry products, which generates livelihood for large number of people. Timber, fuelwood, poles, pulpwood, chipwood, wood for charcoal making, thatching material, fodder, honey, bee-wax, fish, crustaceans, mollusks, shells etc. the main products of the mangrove forests in Thailand. Because of the need for these products, mangroves are exploited. Mangroves play a very important role in the lives and economies of coastal communities as these communities often depend on mangrove forests for meeting their need of aforementioned products as well as the generation of income.
Reasons for Mangrove degradation can be narrowed down to (Menasveta, Piamsak. Mangrove Destruction and Shrimp Culture Systems):
Population expansion: increases in coastal populations have caused the use of mangrove land for various purposes. The needs of increased population had to be met with the destruction of more mangrove areas.
Short- term benefits: conversion of mangroves to fish ponds, rice fields, and salt beds brought higher monetary returns over a short period of time.
Lack of government attention and overall awareness: many government agencies did not manage and regulate use of mangrove lands.
Obscure regulations: government regulations with respect to mangrove lands are often either too complicated or inadequate to ensure the required conservation.
Inefficient reforestation techniques: techniques of restoration of degraded mangrove areas were unknown until the recent past.
In addition to the above reasons, clearance for aquaculture, clearance for salt production, clearance for urban and industrial developments, over-exploitation for firewood, and over-exploitation for charcoal production are other causes of destruction of mangrove forests.
There are many opportunities to slow down the degradation of mangrove. One way of slowing down the degradation of mangrove is to adopt a way to continue with the aquaculture without clearing out the mangrove forest. Shrimp farming is a major part of economic development in Thailand. By using the intensive shrimp culture system, it may prevent the mangroves from being destroyed by extensive shrimp farming. Farmers gradually have come to realize that intensive shrimp culture systems are sustainable systems and that mangroves are unsuitable for such systems. The intensive system uses more advanced technology, requires smaller areas at higher elevation above the high tide level, and does not require mangrove areas. This system is suitable for the areas behind mangroves.
Few ways of contributing to the conservation of mangroves are (http://www.zbindustries.com/mangrove.html):
Plan ahead the location of the aquaculture. Look at the long term benefits and losses instead of short term.
Development of new technologies. With the latest technologies, there’s a good chance of minimizing the negative environmental impacts.
Improving management practices. Knowing how to better manage the mangrove will be useful in getting the maximum use of the mangroves.
Reward policy to those who comply with the best management policy. With incentives to do a better management job than anyone else, everyone will try to apply the best management program.
Encourage the provision of infrastructure in the form of well-designed influent and effluent canals. Many of the problems associated with shrimp farming are related to poor water management. Well-designed water management will be able to dramatically reduce many problems associated with shrimp farming.
Improve training and information to ensure that shrimp farmers are able
to manage their farms for moderate and sustained levels of production.
Earthsummitwatch.Thailand. http://www.earthsummitwatch.org/shrimp/thaipart.html
Kongkeo, H. Comparison of intensive shrimp farming systems in Indonesia,
Philippines, Taiwan and Thailand. Aquaculture research, 1997 Oct.,
V28 N10:789-796.
Menasveta, Piamsak. Mangrove Destruction and Shrimp Culture Systems
Pawputanon, Oophtham http://www.earthsummitwatch.org/shrimp/thaipart.html
The status of mangrove ecosystems Turtles in the soup. Economist March 16, 1996. V338, n7957.
http://193.43.36.7/waicent/fainfo/forestry/wforcong/publi/v6/
http://www.agri-aqua.ait.ac.th/mangroves/
http://www.zbindustries.com/mangrove.html