Banned Banana Crop Pesticides Contaminate Costa Rican Caimans

Global consumer demand for bananas is being linked to contamination in Costa Rica's crocodilians, according to new research published in the journal Environmental Toxicology and Chemistry, which analyzed blood samples from the country's spectacled caiman population and found a connection between intense pesticide use on banana plantations and contamination in caiman living in protected areas.

Study author Paul Grant from Stellenbosch University in South Africa said Costa Rica's banana plantations, which export 1.8 metric tons of the crop -- or 10 percent of the global total -- are a big business.

"The climate of the country's North East is ideal for bananas; however, the Rio Suerte, which flows through this major banana producing area, drains into the Tortuguero Conservation Area," Grant said.

The spectacled caiman (Caiman crocodilus) is one of the most common crocodilian species in Central America. The Tortugero Conservation Area is home to many of the creatures, which are fresh water predators that feed on fish, crustaceans and the occasional wild pig.

Over the past two decades, the global demand for fruit has increased, which has led to a corresponding increase in pesticide usage. The researchers report that in Central America pesticide use has more than doubled in the last 20 years. They add that in Costa Rica, which ranks second in the world for intensity of pesticide use, the problem is compounded by poorly enforced environmental regulations and the country's own unique environmental conditions.

"Frequent heavy rains can wash pesticides from plantation areas, leading to contamination and the reapplication of sprays to the crops," said Grant. "Without adequate enforcement of regulations dangerous practices such as aerial spraying close to streams or washing application equipment in rivers also contributes to contamination downstream."

After collecting blood sampled from 14 adult caiman and analyzing the blood for traces of 70 types of pesticide, the researchers found traces of at least nine kinds of insecticide in the caiman blood. Seven of those nine pesticides were classified as Persistent Organic Pollutants (also referred to as POPS), which are banned under the 2011 Stockholm Convention.

Caiman living within the Rio Suerte, a high-yield banana crop watershed, had a higher pesticide burden compared to caiman living in more remote locations.

"Caiman near banana plantations had higher pesticide burdens and lower body condition," Grant said. "This suggests that either pesticides pose a health risk to caiman, or that pesticides harm the habitat and food supply of caiman, thereby reducing the health of this predator."

Because caiman live near the top of the food chain in the Costa Rican jungles, a more complete understanding of pesticide contamination in caiman can be indicative of pesticide damage throughout the ecosystem.

"Caiman and other aquatic species have been exposed to pesticides from upstream banana plantations, even in remote areas of a national wilderness area," Grant said. "Banana plantations may be economically important to Costa Rica; however their erosion of aquatic ecosystems highlights the need for a developed regulatory infrastructure and adequate enforcement."