Pesticides Float From Distant Farms to Protected Forests, Study Says

March 2, 2007

High levels of pesticides are wafting into protected rain forests in Costa Rica, even though the lowland farms being sprayed with the chemicals are miles away, a recent study reports.

Modern pesticides dissolve more easily in water than older, longer-lasting ones, such as DDT. This means the chemicals break down faster in the environment and are less likely to travel long distances.

But because of a unique atmospheric system created by mountain ranges, large concentrations of pesticides are able to drift with the wind and fall with the rain into sensitive habitats previously thought to be unreachable.

"These chemicals have shown they can make it from the places where they are used to the places that are protected," said study leader Frank Wania of the University of Toronto in Canada.

Wania and colleagues reported their findings in two related papers published in the January 10 issue of the journal Environmental Science & Technology.

Wania said the discovery could explain why amphibian extinctions in Costa Rica's protected forests are more common at higher altitudes.

The findings could also mean that mountain habitats within a dozen or so miles (about 20 kilometers) of agricultural fields anywhere in the world could be at risk of pesticide contamination.

Regional Climate Shifts

Costa Rica's most famous crops have long been bananas and coffee. Luisa Castillo, a study co-author and professor at Costa Rica's National University Pesticide Program, said chemical-intensive production of pineapples is also on the rise.

The small country, which contains about as much land as West Virginia, imports an estimated 9,900 tons (9,000 metric tons) of pesticides a year.

Wania and his team originally went to Costa Rica looking for evidence of older, infamous pesticides such as DDT, many of which were banned by the 2001 Stockholm Convention on Persistent Organic Pollutants.

"Our colleagues in Costa Rica were also worried about what people are using right now," Wania said.

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