One hundred miles away in the Sierra Nevadas, populations of the Pacific tree frog, a native Californian species, have found to have a connection with the Central Valley.

The connection, however, is a bit alarming.

Last week, in a study published in Environmental Toxicology and Chemistry, researchers from the U.S Geological Survey found traces of 10 agricultural chemicals in the tissues of Sierran tree frogs.

The three most commonly found chemicals, pyraclostrobin, tebuconazole and simazine, are all currently used to fight off pests, fungi and weeds on Central Valley farms.

Although the levels found were considered “trace amounts,” the researchers stated that their concern wasn’t that the chemicals were necessarily harming the animals, but the fact that they actually made it that far.

According to lead researcher and hydrologist,  Kelly Smalling, the chemicals found were moved by prevailing winds, and released through dust or precipitation.

DDT (dichlorodiphenyltrichloroethane), an insecticide that was banned nearly 40 years ago, was also found in the tissue samples of the frogs. Prior to this study, neither DDT or the other 10 chemicals, had ever been found in  any frog samples.

However, not everyone agrees that that the study’s results are completely definitive.

Dave Kranz, spokesperson for the California Farm Bureau, said there wasn't necessarily a “link” between exposure and decline of the species.

“Exposure does not necessarily equate to harm,” said Kranz.

Kranz also said that California farmers are under the strictest regulation in comparison to any other state when it comes to the application of pesticides. 

“California farmers operate under the strictest constraints in the nation,” said Kranz. “We are constantly looking for ways to use less pesticides while making more produce.”

Kamaljit Bagri, deputy agriculture commissioner for Stanislaus County, echoed many of Kranz’ concerns regarding the study. Her main source of apprehension was the lack of the herbicide simazine found in groundwater near the area of study. According to Bagri, when simazine levels are high that should show up in the groundwater. However, the researchers found very little traces of any of these elements in the soil or groundwater.

“It’s very hard to say how this could have gotten there,” said Bagri.

Bagri also affirmed that farmers, especially in the Stanislaus County, are practicing the safest methods possible during application of pesticides on their crops.

“We, especially as a county, take the application of these chemicals very seriously,” said Bagri. “It’s our job to apply them safely and we are here to protect the public.”

Even if the chemicals aren't necessarily the cause of amphibian decline, populations of amphibian animals are still disappearing at an alarming rate.

 In another U.S.G.S report done earlier this year, researchers found that amphibians vanished at a rate of 3.7 percent each year.

This could mean that in the next 20 years, half of these species could disappear from their native areas.