Pesticides Float From Distant Farms to Protected Forests, Study Says

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.