Pesticides from Farms Contaminate Frogs in California Parks

Pesticides can spread through ecosystems, carried by water and rain. Now, scientists have found some more disturbing evidence when it comes to this chemical infiltration. They've discovered that remote frog species located miles away from farmland contain pesticides commonly used in California's Central Valley, one of the world's most productive agricultural regions.

Frogs and other amphibians are currently in decline. Recent studies have found that species are disappearing from habitats at an alarming pace. In fact, researchers have estimated that amphibians are vanishing at a rate of about 3.7 percent each year, which means that they will be absent from half of the habitats they currently occupy in about 20 years.

In this latest study, scientists decided to assess the health of the Pacific chorus frog Pseudacris regilla. Found in abundance across California's Sierra Nevada mountain range, this frog can be severely impacted by agrochemicals--like other amphibians.

In order to examine the effect of pesticides on this species, the researchers collected frogs, water and sediment samples from seven ponds ranging from Lassen Volcanic National Park to the Giant Sequoia National Monument. All of the sites were downwind from agricultural areas. They then tested these samples, including the frogs, for 98 types of pesticides.

"Our results show that current-use pesticides, particularly fungicides, are accumulating in the bodies of Pacific chorus frogs in the Sierra Nevada," said Kelly Smalling, one of the researchers, in a news release. "This is the first time we've detected many of these compounds, including fungicides, in these remote locations."

In fact, the scientists found that the frogs contained traces of all 98 of the pesticides from all the sites. This, in particular, is worrisome when it comes to the future of amphibians. The researchers also found a breakdown product of DDT, called DDE. This chemical was banned in the U.S. in 1972 so the fact that it continues to persist in the ecosystem shows how long DDT can continue to impact biodiversity.

"Very few studies have considered the environment occurrence of pesticides, particularly fungicides which can be transported beyond farmland," said Smalling. "Our evidence raises new challenges for resource managers; demonstrating the need to keep track of continual changes in pesticides use and to determine potential routes of exposure in the wild."

The findings are published in the journal Environmental Toxicology and Chemistry.