Aquaculture for all

Carbon Footprint for Farmed Shrimp Disputed


US - A presentation by ecologist J. Boone Kauffman of Oregon State University at the 2012 meeting of the American Association for the Advancement of Science has led to a series of sensationalized and misleading articles about the impacts of shrimp farming, says the Global Aquaculture Alliance (GAA).

While the Global Aquaculture Alliance does not dispute Mr Kauffman's concerns about the carbon footprint of converting mangroves to other uses, GAA challenges his assumptions regarding the role of shrimp farming in such conversions.

Mr Kauffman's briefing paper said that 50 to 60 per cent of shrimp farms are constructed in former mangrove areas, have annual productivity of just 50 to 500 kilograms per hectare and are abandoned in just three to nine years. By combining these erroneous assumptions, he concluded that the release of carbon dioxide through conversion of mangrove land to shrimp ponds yields a 198-kilogram footprint per 100 grams of edible shrimp.

"It is important to understand how far off those numbers are," Mr Chamberlain said.

In research with World Wildlife Fund's Jason Clay, aquaculture scientist Claude Boyd estimated that less than 10 per cent of historic mangrove loss resulted from shrimp farm construction. The practice of converting mangrove areas to shrimp ponds essentially stopped almost two decades ago due to strong regulatory and industry pressure. The main causes of mangrove loss are agriculture, salt evaporation ponds, mining and infrastructure development.

Although common in the 1980s, low-density culture methods as described by Mr Kauffman are currently confined to limited areas of Bangladesh, Indonesia and southern Viet Nam, and now represent only a few per cent of the total global shrimp harvest.

It is inaccurate to assume that shrimp ponds have a lifespan of three to nine years, Dan Lee, GAA Best Aquaculture Practices standards coordinator, said. While shrimp farms built in mangrove areas are inherently inferior to higher-elevation ponds due to acid sulfate soils and limited drainage, they become less problematic over time as the acid gradually neutralises. Mangrove ponds in Ecuador and Honduras are still in operation after 40 years, and traditional "tambak" ponds have produced fish and shrimp in Indonesia for hundreds of years.

"While the Global Aquaculture Alliance supports Mr Kauffman's valuation of mangroves as important ecological carbon sinks that should be conserved, we take issue with his calculations about shrimp farming," Mr Chamberlain said. "His assumptions bear little relation to today's shrimp-farming industry, which has long since moved away from the mangrove zone. It's akin to calculating soil erosion for US agriculture based on the Dust Bowl practices of the 1930s."

Mr Kauffman's numbers were quickly distributed by various media entities, often within articles with anti-shrimp headlines. In addition, some inattentive editors incorrectly reported his data and claimed that only 1 kilogram of shrimp is produced in 13.4 square kilometers of pond - an absurd statistic.

"It is very unfortunate that these misleading messages are being circulated," Mr Lee said, "GAA sincerely hopes that when consumers and others read such material, they can recognise how outdated and distorted it is."

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