New pesticides from the Central Valley found in remote Sierra Nevada frogs


Amphibians are vanishing at an alarming rate, even from areas we think of as pristine and protected. California’s Sierra Nevada is a prime example of this global problem—five out of seven amphibian species there are threatened. Researchers are still trying to pinpoint exactly why ponds that once held mountain yellow-legged frogs or California red-legged frogs are now devoid of amphibians.

In a new study, a U.S. Geological Survey group focusing on how pesticides affect amphibians tested common Pacific chorus frogs and their habitats, including Yosemite National Park and Giant Sequoia National Monument, for around 100 agricultural chemicals. Even though researchers have looked at pesticides in Sierra Nevada amphibians for years, the new study’s most commonly detected chemicals, two fungicides and one herbicide, have never been found in amphibians until now.

“As pesticide use changes, our studies have to evolve as well,” says Kelly Smalling, a USGS hydrology and chemistry researcher, and the lead author on the study. As new pesticides are approved, it's difficult to keep pace with where they end up in the environment, so the USGS group tested for a large batch of them in seven remote locations. “That’s how we stumbled across the fungicides.” In 2005, the U.S. Environmental Protection Agency approved the two fungicides found in the new study, pyraclostrobin and tebuconazole, to combat a new soybean rust -- the spores of which may have landed in the U.S. from South America during the 2004 hurricane season.

Pesticides, and diseases like the chytrid fungus, plus habitat loss and climate change, are among the possible reasons amphibians are blinking out in pristine areas. Earlier studies established that pesticides get into Sierra Nevada snow, water and sediments by wafting from the Central Valley, one of the nation’s most intensive agricultural regions. Frogs downwind of the valley are declining more rapidly than coastal or northern frogs.

Researchers also found in previous studies that pesticides commonly applied in the Central Valley, chlorpyrifos, and DDT-like endosulfan (which is being phased out), showed up in declining populations of Sierra Nevada Pacific chorus frogs, and also in imperiled yellow-legged frogs. Smalling's study only looked at Pacific chorus frogs because they are not threatened, and so the population wouldn't be harmed by a few sampling causalities. Yet the work still may point the way to research that could help narrow down what’s harming more rapidly declining species like yellow-legged frogs.

The next step, according to Smalling, is figuring out how the fungicides could affect, or kill, amphibians. That means a lot of difficult laboratory work, partly because every frog species may respond to pesticides differently.

As for how pathogens like the chytrid fungus might be interacting with pesticides to kill frogs, that remains a mystery. “I think it’s quite likely that there is an interaction between pesticides and other stressors,” says Gary Fellers, a wildlife biologist on the study who has worked on amphibian declines since the ‘90s.

Fellers, who recently retired from the USGS, grew up backpacking in Yosemite, where he still does field work. “I know of frog populations that are entirely gone now,” he says. “I’m incredibly anxious to find what’s causing these declines before we lose entire species.”

Sarah Jane Keller is the editorial fellow at High Country News.

Eric Mills
Eric Mills
Aug 01, 2013 06:29 PM
We didn't learn a damned thing from Rachel Carson and SILENT SPRING, did we? And is anyone so naive as to believe that it's only the frogs which are being affected by all these dangerous pesticides?

Relatedly, California imports some TWO MILLION non-native American bullfrogs for the Chinatown live food markets. Recent studies have documented that the majority are infected with the chytrid fungus (Bd), thought to be responsible for the extinctions of 200 or so frog and other amphibian species worldwide in recent years. This has been pointed out repeatedly to the California Dept. of Fish & Wildlife and the Fish & Game Commission, yet the commerce continues unabated. Can you spell "dysfunctional"? Many of these frogs are released into local waters where they prey upon and displace our native wildlife, while spreading diseases. Even now, Australia and the European Union allow the importation of only FROZEN frog parts for food. The U.S. should do likewise.

CONTACT: Chuck Bonham, DFG Director:
Michael  Kemly
Michael Kemly
Aug 05, 2013 10:07 PM
Dr. Richard Leake Jr. Famous paleontologist said, "Extinction of all species is inevitable."
So enjoy yourself, buy a Cadillac, eat Boston cream pies and have sex when you can! Enjoy.
Carolyn Poissant
Carolyn Poissant Subscriber
Aug 06, 2013 01:36 PM
Maybe if you are an ostrich. I'd prefer to see species thrive in this incredible planet we call home.
Kirk Hohenberger
Kirk Hohenberger Subscriber
Aug 06, 2013 02:11 PM
We use to be able to grow our food without chemicals, herbicides, and pesticides , GMO"s,Why can we now not do that? If there is a reason , that is a big canary.More then likely we can, with less yield, so what, most of the food we produce goes overseas, is it out responsibility to feed the planet? We have certainly the land to feed Americans without killing the soil, animals, and eventually ourselves.
David Olsen
David Olsen
Aug 06, 2013 02:50 PM
We will likely soon have an overabundance of wheat and other food traditionally sent overseas for aid as new government policy will soon be to send money instead. "American food aid has traditionally meant buying American food and shipping it to areas of need. But the Obama Administration realizes that it's better to have cash than to have stuff. American dollars could help more people and do more good if we had the flexibility to spend aid dollars in whatever way is most appropriate to a crisis."

Kirk Hohenberger
Kirk Hohenberger Subscriber
Aug 06, 2013 02:55 PM
The way we farm in this country should be outlawed , it should be a crime. This type of industrial mono- culture Scorched earth roundup killed every living plant other then the one Species grown , then pesticide any insect , leaves nothing living but that one crop. Multiply that by hundreds of millions of acres, and this type of farming is the single greatess reason for plant and animal declines. The reason we do this is money and profit over everything else. With no regard , to ourselves, animals , or the planets Sustainability.
Kirk Hohenberger
Kirk Hohenberger Subscriber
Aug 06, 2013 03:38 PM
We need a new Economic model, based on Sustainability. Capitalism is modeled after never ending growth, Unsustainable, making as much money as you can, as quick as you can. use up all your resources as fast as you can, so you can make more money now, oil and gas extraction, now even planning on exporting our kids oil to make more money now. thinking of conservation of leaving resources for future generations ,if there are profits to be made now,and jobs.what good is all this if it is all the money and jobs if it is all gone in a hundred years? Incredibly self-serving and shortsighted.