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Bananas are the world’s most popular fruit.  They are also vital to the economies of the countries that farm them.  However, growing bananas might be causing significant harm to Costa Rican wildlife. A new study published in suggests that the pesticides used in banana farming are leaching into streams and canals downstream, and showing up in the bloodstreams of Costa Rica’s crocodile, the spectacled caiman.

Even though it is a small country, Costa Rica exports approximately 1.8 million tones of bananas a year.  Filling those orders requires huge quantities of pesticides to combat pests and diseases that thrive in the warm, wet climates where the bananas grow. One particularly nasty fungal disease, called black sigatoka, can devastate a plantation in a few weeks. The demand for bananas has been increasing over recent years, aggravating the problem of pesticides and raising environmental concerns.

“Frequent heavy rains can wash pesticides from plantations areas, leading to contamination and the reapplication of sprays to the crops,” explained lead author and biologist, Paul Grant, to .  He added that he had previously witnessed massive fish die-offs as a result of pesticide exposure, and became interested in researching the effects on animals further up the food chain. 

The spectacled caiman, which gets its name from the bony ridge between its eyes, was a prime candidate for study because it is one of the most common top predator species feeding on fish in the area.  It is also particularly long-lived and is listed as a threatened species according to the . 

The study was conducted over three months, during which the scientists collected blood samples from 14 caimans; some close to the plantations and others further downstream.  Researchers analyzed the blood for 70 different pesticides, and found traces of nine to be present.  However, only two of them were pesticides in current use. 

The remaining seven included chemicals, such as DDT, dieldrin and endosulfan, which have been banned for years under the 2011 Stockholm Convention. This meant that the chemicals not only leach into the ecosystem, but also persist in the environment, sometimes as long as a decade. The results also showed the caimans close to the plantations were consistently in poorer health.

“Caiman near banana plantations had higher pesticide burdens and lower body conditions,” said Grant to .  “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.”

The researchers claim that this has become a critical situation and highlights urgent need for regulations and enforcement in order to reverse the problem, or at least contain it.