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Weathering a sea change

To understand the scale of change in the coastal zone of tropical Asia, South America and Africa, look no further than the dinner tables of the United States. Shrimp, once an expensive delicacy, has surpassed canned tuna to become America's favourite seafood, and per capita consumption has doubled in a decade. To meet burgeoning demand for shrimp in the US, Japan and elsewhere, farmers have taken up aquaculture around the world, especially in the tropics. As recently as the early 1980s, capture fisheries supplied almost all of the world's tropical shrimp. By 2002, aquaculture filled 43 per cent of this greatly expanded market.

Shrimp's growing popularity is reshaping the tropical coastal zone
Shrimp's growing popularity is reshaping the tropical coastal zone

"Shrimp farming is perceived as both a success story - developing from a backyard production system to global industry in only 30 years - and a tragedy responsible for serious negative environmental and social consequences," said Dr. John Gowing of the University of Newcastle upon Tyne. Gowing was speaking at the International Conference on Environment and Livelihoods in the Coastal Zones: Managing Agriculture-Fishery-Aquaculture Conflicts*, which took place in Bac Lieu, Vietnam, in March.

Mangrove loss

Mangrove loss has many causes, but the spread of shrimp aquaculture is widely blamed for the accelerated depletion of recent decades. Estimates of national mangrove loss run as high as 84 per cent in Thailand, long the world's largest shrimp producer (now overtaken by China). Shrimp farmers typically dig their ponds in mangrove areas under murky or poorly enforced ownership and access regimes. Conversion displaces the often landless poor who depend on gathering mangrove products, and pond effluents spoil much of the remaining mangrove. As acidification, pollution and disease render ponds unproductive, shrimp farmers - or their wealthy financial backers - abandon them to dig up mangroves elsewhere. And so the destruction spreads.

"Conversion of mangroves to shrimp farms is largely irreversible," observed Dr. Edward Barbier of the University of Wyoming at the Bac Lieu conference. "Without careful ecosystem restoration and manual replanting, mangroves do not regenerate in abandoned shrimp-farm areas."

How mangrove loss and aquaculture effluents affect capture fisheries is poorly understood. Paul van Zwieten of Wageningen University reported that research into the effect of rapid and massive conversion of the Mahakam Delta in Indonesia failed to document any clear change in local fisheries' overall productivity. "Trade-offs between shrimp culture, fisheries and biodiversity conservation are real," he concluded. "However, the ecological interactions are difficult to quantify."

Social upheaval

Several presentations at the conference focussed on aquaculture's effect on farm communities. A gold rush mentality has seen Asian rice farmers turn to shrimp because the crop is vastly more profitable than rice. Unfortunately, shrimp farms also have a much higher failure rate - 70 per cent in Vietnam. Unable to repay their loans, many farmers end up forfeiting their land. The decline of local agriculture worsens the pressure on fisheries. "Women who have lost employment in agriculture because of conversion to shrimp farming resort to collecting fry to sell to shrimp farmers," said Dr. Md. Rezaul Karim of Khulna University in Bangladesh. "By-catch results in great loss of other species."

A farmstead in Vietnam's Mekong Delta
A farmstead in Vietnam's Mekong Delta

"The social upheaval and resulting landlessness raises a methodological problem for any impact assessment of aquaculture," argued Cecilia Luttrell of the Overseas Development Institute. "Those who have been most adversely affected have often moved on and are therefore not included in the assessment. However, given the rapid expansion of aquaculture in Vietnam, the question perhaps is no longer only whether or not to encourage aquaculture but, rather, how it can be designed to safeguard against negative social impacts."

In extensive shrimp farming, up to three shrimp per square metre feed largely on the natural fertility of the pond. Most conference participants agreed that this relatively benign practice is sustainable - or it would be if, as some contended, financial pressures did not push shrimp farmers inexorably toward intensification.

Coastal stewardship

Good resource-management policy depends on knowing stakeholders' priorities. "Planners often focus on food production, primarily tonnes of rice," explained Dr. Eric Baran of the WorldFish Centre. "But for most farmers, production also means contribution to income, and in Vietnam a kilogram of shrimp is worth about 50 kilograms of paddy. For provincial managers, sustainable production implies balanced land use promoting development. And for the poorest, landless stakeholders, the often overlooked wild fish in streams and canals are essential to sustenance."

Coastal communities are well aware of the importance of managing natural resources sustainably. The challenge for researchers and policymakers is to develop and establish land-use and resource-extraction regimes that instil confidence in farmers, fishers and gatherers that behaving responsibly today will indeed bring benefits tomorrow.

"Coastal stewardship is one way of reducing conflicts by promoting ownership," concluded Dr. Ian White of Australian National University. "It involves voluntary compliance, strong commitment and willing participation in the sustainable use of coastal resources underpinned by clear regulations and laws. The challenges in coastal stewardship are to inform, educate, motivate and empower communities to become managers and custodians of their environment."

*Organised by the International Rice Research Institute (IRRI), International Water Management Institute (IMWI), Cantho University, and People's Committee of Bac Lieu Province, and sponsored by the Comprehensive Assessment of Water Management in Agriculture, Challenge Programme on Water and Food, WorldFish Centre, IRRI and IMWI.

Date published: May 2005


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