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A spectacled caiman.

A spectacled caiman, Caiman crocodilus, sits partially submerged in water. Pesticides are threatening the Costa Rican caiman population.

Photograph by John Cancalosi, National Geographic

Allie Wilkinson

National Geographic

Published September 30, 2013

Bananas are big business for Costa Rica, bringing in hundreds of millions of dollars each year. But the bright yellow fruit could spell trouble for the country's caimans, a crocodile relative.

New research from the journal Environmental Toxicology and Chemistry found that spectacled caimans (Caiman crocodilus) near banana plantations were significantly thinner, and had higher pesticide concentrations in their blood, than caimans in more remote locations. (Watch a video about banana farms in Costa Rica.)

"The animals are very, very thin—about 50 percent thinner than those away from the plantations," said study co-author Peter Ross, an aquatic ecotoxicologist and associate professor at the University of Victoria in British Columbia.

It's unclear whether the pesticides are directly toxic to the caimans or are impacting their health indirectly by diminishing the quality and abundance of their food supply.

Ross thinks the latter scenario is more likely given the moderate pesticide concentrations he and his colleagues found. Since all of the pesticides detected were insecticides, the chemicals could be knocking out the bottom of the food chain. This would affect the fish that eat the insects, resulting in caimans having to search farther for food and use more energy to try to find the few fish that remain.

A Banana Bounty

With its warm temperatures, bountiful rainfall, and good soil, Costa Rica is a prime location for banana production. As a key export, bananas play an important role in the nation's economy. In 2011, Costa Rica exported 2 million tons (1.9 million metric tons) of bananas, valued at over $700 million.

 

 A banana plantation in the lowlands of eastern Costa Rica.
A banana plantation in the lowlands of eastern Costa Rica. Pesticides from plantations like this may be hurting the local caiman population.

Photograph by Buddy Mays, Alamy

 

As demand for the fruit increases, so does pesticide use. In the last two decades, pesticide use in Central America has doubled. Costa Rica ranks second in the world for intensity of pesticide use; and bananas, which lack the genetic diversity to fight off pests, receive some of the heaviest doses of any crop in the world.

Lack of infrastructure and enforcement regulating the use of these chemicals have contributed to environmental contamination. And the country's frequent heavy rains wash the pesticides from target areas such as banana plantations and into nearby waterways.

In the northeast region of Costa Rica, the chemicals from the banana plantations appear to be winding their way down the Rio Suerte river (map) and into the Tortuguero Conservation Area, one of the most important wilderness areas in the country. This species-rich area provides critical habitat for many organisms on the IUCN Red List, including the spectacled caiman.

Ecosystem Sentinels

Caiman are ideal markers for the health of the ecosystem due to their abundance, longevity, and role as a top predator, said Paul Grant, lead study author and a doctoral candidate at Stellenbosch University in South Africa. Any habitat disturbances or stresses are reflected in caiman populations, and are thus easily observed. (Watch exclusive video of a jaguar killing a caiman.)

Grant and colleagues collected blood samples from 14 caiman and analyzed the samples for 70 current-use and legacy pesticides and breakdown products. Of the nine pesticides detected in caiman blood, seven were listed as persistent organic pollutants and banned under the Stockholm Convention adopted in May 2001.

"The reason the Stockholm Convention exists is because these types of chemicals are readily transported through the air and can end up in remote, pristine environments," said Ross.

The presence of pesticides in the caimans' blood wasn't surprising to Ross. "Wherever we look in the world, we run into pesticides and industrial chemicals," he said.

But while the pesticide concentrations researchers detected were moderate, the detrimental effects observed in caiman may signal consequences for the entire ecosystem. Pesticide exposure has been linked to disease susceptibility, reproductive failure, developmental abnormalities, and die-offs.

We don't know the level at which those multiple pesticides start to be a problem for the plants and animals in an area, said Grant, or how sensitive each organism will be to varying levels of the chemicals.

The fact that caiman are being impacted indicates that other aquatic organisms are going to be affected as well, he added. "There’s fairly strong evidence that pesticides, whether it's indirect or directly, are eroding caiman habitat."

6 comments
Phil Moore
Phil Moore

It is obvious the pesticides come from the huge banana plantations nearby, controlled by corporations such as Chiquita, Del Monte, Dole, etc., and are killing the ecosystems, just to provide cheap fruit for the US and European markets. Where else would they come from, grandma's orchard?

Time to boycott all bananas, pineapples and other cheap fruit from such plantations, especially those that use illegal pesticides and destroy the environment and the health of local communities.

antoinette amegbletor
antoinette amegbletor

The caimen need to be saved also other fauna and floras that are affected.

By that the ecosystem will keep its balance.

john farrell
john farrell

The climate of Costa Rica and the apparent ease in which these chemicals migrate throughout the ecosystem would seem to affect the potential for Costa Rica to develop an "organic" banana industry in such areas.  Even if the chemicals are not used on the plants themselves, it appears that these persistent chemicals are still present throughout the environment.  This raises the question, as to how to ensure organic produce is not contaminated from past abuses.  We certainly do not need pristine areas deforested and exploited for organic farming either. Perhaps a Costa Rican government program to move these polluting operations out of the watersheds of the reserves is needed.  There is no simple answer to this problem.

Anne Vezina
Anne Vezina

If the pesticides found in the caimans are banned organochlorines that are commonly found throughout the food chain, why mention that pesticide use in banana plantations has increased in the past 20 years? Are you implying that the industry has been using these banned organochlorines? The authors of the study did make that link in their scientific paper, but failed to provide evidence to support it (see a critique of their paper at http://www.promusa.org/tiki-view_blog_post.php?postId=314). 

This article similarly fails to provide evidence that the demand for bananas is putting the caimans of Costa Rica at risk, contrary to what the title claims.  

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