How the hunt for seafood is ravaging a tropical island

Poorly controlled shrimp farms are causing widespread damage

Surrounded by mangroves, the tropical island of Muisne, off Ecuador's northern coast, sounds like an idyllic place to live. Fishermen repair their nets on its palm-fringed beaches while "ecological taxis" – tricycles with passenger seats – patrol the unpaved streets; no motorised transport exists on the island. Yet Muisne and its Afro-Ecuadorian community of 8,000 are in decline. As the years roll by, there are fewer fish and shellfish to catch, the water becomes more polluted and a growing number of locals desperate to eke out a living migrate to the mainland, or leave Ecuador altogether.

Feeding the developed world's seemingly insatiable demand for cheap seafood, shrimp farms have ravaged Muisne's delicate mangrove ecosystem and turned its inhabitants from a poor but close-knit community to one scarred by a disturbing string of social ills.

"There is more poverty, more pollution, more alcoholism and more prostitution. This has been a curse for our community," says Lider Gongora, a Muisne resident and the executive director of CCONDEM, the national umbrella group that campaigns for mangrove communities. "It has devastated the local economy. Muisne is poorer as a result of the shrimp farms, and it is the same for all of Ecuador's communities that depend on mangroves."

In the 1970s, before shrimp farms arrived, the island had 20,000 hectares of mangroves. Now there are just over 5,000 hectares, nearly half of which is secondary forest, replanted by the community. From Indonesia to Brazil, the story is the same. Yet nowhere has the growth of farms for shrimp, prawns, salmon and other species been as explosive as in Latin America and the Caribbean. According to the UN's Food and Agriculture Organisation, production in the region grew annually at 21.1 per cent between 1970 and 2008. Over the same period, annual global consumption of farm-reared seafood has risen from 700g to 7.8kg per capita.

Meanwhile, more than half of the world's estimated 32 million hectares of mangroves – one of the most biodiverse and fragile ecosystems – has been lost. In Ecuador, fewer than a third of the country's initial 360,000 hectares of mangroves survive. And in Honduras, scene of some of the least regulated shrimp farm expansion, which has led to a string of unresolved murders of fisherman, now has just a quarter of its 250,000 hectares of mangroves still standing.

The shrimp farms typically have a complex series of environmental impacts. Initially, sections of the mangrove are cleared to make way for the farms. Once operational, the farms may use large quantities of antibiotics and pesticides that often contaminate the surrounding forests. Farms can also obstruct the flow of rivers and streams, preventing them from mixing with seawater to provide the brackish water that mangroves need to thrive. In doing so, they provide a double whammy by stopping the farms' pollutants from being washed away, increasing the ecological devastation while the shrimp and prawns are reared in a cocktail of chemicals, stale water and bacteria.

As the mangroves' delicate ecological balance is disrupted, the effects can reach far beyond these unique, coastal forests. Many of the myriad species of fish, birds, reptiles, amphibians, and insects found in mangroves spend only one stage of their life there, hatching or breeding before migrating to other biomes, such as the open sea, nearby salt flats or inland forests.

The impact for Muisne has been depressingly predictable. Fishermen who wade waist-deep through the mangroves' soupy, opaque waters looking for black scallops have to spend longer and longer to catch less and less. Previously, one fisherman could harvest up to 2,000 scallops a day but now, working longer hours, it is 150 at most. "Sometimes you spend the whole day but don't get anything," complains Mr Gongora.

Despite the 2006 election of a leftist president, Rafael Correa, and the subsequent, groundbreaking rewriting of the constitution to include the "rights of nature", shrimp farming in Ecuador has actually increased, following a new law to expand production to fresh stretches of the country's Pacific coast. "Correa has his left-wing, environmentalist discourse but it is a big lie," Mr Gongora says, bitterly. "He justifies the shrimp farming by saying it brings foreign exchange, but what is the cost to Ecuadorians?"

Some Western businesses already appear to be heeding the environmentalists' message. Britain's largest retailer, Tesco, sources some of its shrimp and prawns from a Latin American farm (it will not reveal in which country) that it claims is the first organic shrimp hatchery and uses no antibiotics or pesticides. "We want to be selling seafood to our customers in 50 years' time so it's in our interest to ensure we're sourcing it responsibly," a spokesman for Tesco said.

But for some, shrimp farming's new age of corporate social responsibility may be too little, too late. In Honduras, possibly Latin America's most lawless country, shrimp farms continue to be built inside coastal areas protected under the UN's Ramsar Convention on Wetlands.

"There has been total impunity," says Jorge Varela Marquez, the head of an environment group in the Gulf of Fonseca, on Honduras's Pacific coast. "Whenever these cases have gone to court, the justice system has been completely partial and favoured the shrimp farms."

And Mr Varela Marquez's message to British consumers could not be blunter: "Pay a fair price for shrimp and stop drinking the blood of our people."