A study published this week in the online science journal Environmental Toxicology and Chemistry found that pesticides used on banana farms in Costa Rica are ending up in the bodies of caimans living in nearby rivers.
For three months, wildlife biologist Paul Grant and scientists from British Columbia studied the effects of pesticides on local wildlife in the northeastern region of Costa Rica. The team collected blood samples from 14 adult caimans in the Tortuguero Conservation Area, located just downstream from some of the biggest banana farms in the country.
Grant and his colleagues analyzed blood samples for 70 different pesticides. Nine of those pesticides showed up in the blood samples, although only two are currently used in banana farming. The other seven are “historic organic pollutants,” researchers said.
Among those are DDT, dieldrin, and endosulfan, some of which have been banned for nearly a decade. Yet the chemicals remain in the environment and have accumulated in the body tissue of local animals.
The study concluded that pesticides used on banana plantations are “impacting a high trophic-level species inhabiting one of the most important wilderness areas in Costa Rica.”
“In the past I have witnessed, and a lot of the locals have pointed out, that there have been massive fish kills as a result of pesticide exposure in high levels,” Grant said.
While in Costa Rica researchers also wanted to find out if pesticides are ending up in animals that eat the fish. In particular, Grant said he was interested in the spectacled caiman (Caiman crocodilus), named for a bony ridge between its eyes, which makes it appear that it’s wearing eyeglasses.
The animal is considered a threatened species by the International Union for Conservation of Nature. Adult caimans are considered a “keystone species” because of their place at the top of the food chain and the role they play in controlling certain prey populations.
Researchers said that global demand for bananas, especially in the United States, isn’t healthy for Tico caimans. Bananas are Costa Rica’s top exported fruit, according to the U.S. Agricultural Marketing Resource Center.
In addition, Costa Rica remains one of the world’s leading banana exporters. In 2012 the country exported 107 million banana boxes, 42.9 percent of them to the U.S. Banana exports from Costa Rica have continued to increase over the last decade, including a peak of 114 million boxes in 2007, according to the National Banana Corporation.
Conditions in Costa Rica – along with countries like Ecuador and Brazil – are perfect for growing bananas, due to warm weather and abundant rain.
Despite the findings, scientists point out that pesticides are found in significant levels across the globe in all sorts of aquatic animals, including crocodiles, whales and seals.
“The overall levels of pesticides found in Costa Rican caimans in comparison [to animals around the world] were modest,” researcher Peter Ross, an environmental scientist at the University of Victoria in British Columbia, told National Public Radio in an interview earlier this week.
“What was revealing to me was the fact that the caimans that were near banana plantations had not only higher concentrations of pesticides, but also they were in a poorer state of health relative to caimans in more pristine, remote areas,” Ross said.
This suggests that either pesticides elicited toxic effects in caimans, resulting in diminished overall health, or that the quantity or quality of their prey was reduced by pesticides downstream of plantation waterways.
Christian Robles Puchi, wildlife conservation director at the Tortuguero Conservation Area (part of Costa Rica’s National System of Conservation Areas), said there are no reports of largescale damage to species in the region, but “it is a real possibility considering the nearness of monocrop-oriented farms.”
Heavy rainfall also is an important factor, as rains wash residual pesticides from farms to nearby rivers, Robles added. But he stressed that, “So far, [researchers] have not detected any mayor affectation in mortality rates.”
Chris Wille, chief of sustainable agriculture at Rainforest Alliance, said that there’s a reason why banana plantations rely heavily on pesticides: Banana plants are particularly susceptible to infestations, and most plantations are in the tropics, “where there are a lot more kinds of pests, worms and fungi, and [they’re] in abundance.”
“We’re now reckoning with the problem left by past use of highly toxic, highly persistent pesticides,” Wille said. “So, what plantations must avoid now is leaving similar toxic legacies for the next generation to deal with.”
The study, “Pesticides in blood from spectacled caiman (Caiman crocodilus) downstream of banana plantations in Costa Rica,” by Paul B.C. Grant, Million B. Woudneh and Peter S. Ross, is available for download at Wiley Online Library.