Pesticide Harmful to Amphibians is Banned in U.S.

Last week the U.S. Environmental Protection Agency announced that it would ban the use of endosulfan. Endosulfan is an organochlorine pesticide that was developed in the 1950s. Although it is an effective compound against many crop pests it comes with serious health risks to humans and wildlife, including acute neurotoxicity and endocrine disruption. As a consequence endosulfan is banned in more than 63 countries, including the European Union.

Several studies indicate that because endosulfan persists in the environment for years it can be transported long distances from application sites. For example, endosulfan is commonly detected in the Sierra Nevada despite the fact that it is not applied anywhere nearby. The idea that endosulfan detected in the Sierra Nevada originates from applications in upwind agricultural areas is supported by the fact that endosulfan concentrations in the Sierra Nevada correspond very closely with application rates in the Central Valley, with a lag time of 1-2 weeks.

The fact that endosulfan can disperse widely and persist in the environment has long raised concerns about its effects on wildlife. Research on its impacts on amphibians in the Sierra Nevada indicates that endosulfan is detectable in Pacific treefrog populations (Pseudacris regilla) throughout the range and is toxic to amphibians at extraordinarily low concentrations. However, a just-published study indicates that concentrations in frog tissues are generally well below levels that would cause direct or indirect impacts. 

Overall, the effects of endosulfan on Sierran amphibians is likely relatively minor compared to those caused by trout introductions and the amphibian chytrid fungus (Batrachochytrium dendrobatidis). But given its broad toxicity to wildlife and humans the ban on endosulfan use was nonetheless long overdue. 

The following publications provide additional information on the effects of pesticides on amphibians in the Sierra Nevada:

Bradford, D. F., E. M. Heithmar, N. G. Tallent-Halsell, G.-M. Momplaisir, C. G. Rosal, K. E. Varner, M. S. Nash, and L. A. Riddick. 2010. Temporal patterns and sources of atmospherically deposited pesticides in alpine lakes of the Sierra Nevada, California, U.S.A. Environmental Science and Technology 44:4609-4614.

Bradford, D. F., K. Stanley, L. L. McConnell, N. G. Tallent-Halsell, M. S. Nash, and S. M. Simonich. 2010. Spatial patterns of atmospherically deposited organic contaminants at high elevation in the southern Sierra Nevada mountains, California, USA. Environmental Toxicology and Chemistry 29:1056-1066.

Davidson, C. and R. A. Knapp. 2007. Multiple stressors and amphibian declines:  dual impacts of pesticides and fish on yellow-legged frogs. Ecological Applications 17:587–597.

Davidson, C., H. B. Shaffer, and M. R. Jennings. 2002. Spatial tests of the pesticide drift, habitat destruction, UV-B, and climate-change hypotheses for California amphibian declines. Conservation Biology 16:1588-1601.

McConnell, L. L., J. S. Lenoir, S. Datta, and J. N. Seiber. 1998. Wet deposition of current-use pesticides in the Sierra Nevada mountain range, California, USA. Environmental Toxicology and Chemistry 17:1908-1916.

Sparling, D. W. and G. Fellers. 2009. Toxicity of two insecticides to California, USA, anurans and its relevance to declining amphibian populations. Environmental Toxicology and Chemistry 28:1696–1703.

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A Busy Week in the Media for California Amphibians and Fish

The media was abuzz this week with frog and fish-related stories. First came the news that the California Fish and Game Commission voted 3-2 to support the listing of the California tiger salamander as "threatened" under the California Endangered Species Act (Santa Rosa Press-Democrat story). Because this species is already federally-listed I don't think this will change the existing management significantly.

And then last Tuesday there was an excellent discussion about nonnative fish impacts on NPRs Diane Rehm show (archive available here). This show topic was prompted by the publication of the book, "An Entirely Synthetic Fish: How Rainbow Trout Beguiled America and Overran the World", by Anders Halverson. This is a must-read book that provides an exploration of the history, biology, and sociology of trout aquaculture and stocking. Anders was joined on the show by Curtis Milliron from the California Department of Fish and Game and Gerald Smith from the University of Michigan, and the three of them contributed to a lively discussion. 

And finally, we had the publication of a new study by Tyrone Hayes (UC Berkeley), this one showing that exposure of frogs to low doses of the herbicide atrazine can result in complete feminization of males. The authors state, "Ten percent of the exposed genetic males developed into functional females that copulated with unexposed males and produced viable eggs." These results are remarkable and scary. If atrazine causes these bizarre effects in frogs, what effects does this stuff have on humans?

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Amphibian Decline Movie - Sadness and Hope

I watched the film, "Frogs: The Thin Green Line", last night. Filmmaker Allison Argo and her team did an amazing job of bringing the amphibian decline issue to a general audience. Despite how dire the situation is I was left with a feeling of hope that collectively we just might make a difference. As usual, time will tell.... The film can now be viewed online on the PBS web site.

As I mentioned recently on The Mountain Yellow-legged Frog Site, the April issue of Fly Rod & Reel magazine has an article by renowned conservation writer, Ted Williams, on the lawsuit over fish stocking in California that was recently won by the Center for Biological Diversity and the Pacific Rivers Council. This is far and away the best article written so far on this issue. I've been hoping that this article would soon be posted on the Fly Rod & Reel web site, but that hasn't happened yet. So, here is a scanned copy of the article (PDF). Additional details on this topic are available on the California Department of Fish and Game web site and in my 4/18/08 and 11/21/08 Frog Blog posts.

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Global Amphibian Declines - The Movie

During the past year filmmaker Allison Argo and her team have been traveling around the world to film declining amphibians and find out from scientists what can being done about it. In addition to filming in Panama and the southeastern U.S., Allison's team also spent a few days with my research group while we conducted research on Sierra Nevada yellow-legged frogs in Yosemite National Park. The resulting film, "Frogs: The Thin Green Line" will be shown for the first time on April 5 (this Sunday) on PBS. Allison's previous films on amphibian declines (The Last Frog), declining shorebirds (Crash: A Tale of Two Species), and other wildlife-related topics were extraordinarily good, so I suspect that this latest film will be well worth watching. Hopefully Allison didn't include the footage of me falling into the pond.... On 3/31,the film's creators posted a podcast from "behind the scenes". Check it out.

If you do watch the film, feel free to post your reviews and thoughts here.

Now to the task of finding a friend who owns a TV....

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Contaminants in Western National Parks

Airborne contaminants are suspected of contributing to the declines of amphibians, including the mountain yellow-legged frog in California's Sierra Nevada. Research on this important topic has been hindered by a lack of information on what contaminants are actually present and at what concentrations.

The final report of the Western Airborne Contaminants Assessment Project (WACAP) was released on February 28. Entitled, "The Fate, Transport, and Ecological Impacts of Airborne Contaminants in Western National Parks (USA)", this report is an eye-opener. The six year study focused on eight core parks and 12 secondary parks, stretching from Noatak National Preserve in northern Alaska to Big Bend National Park in southern Texas. Samples of air, snow, water, lake sediments, lichens, conifer needles, and fish were sampled for dozens of current-use pesticides, historic-use pesticides, industrial/urban compounds, combustion by-products, and heavy metals. The resulting dataset allowed analyses at an unprecedented spatial scale. For the sake of brevity, I'll summarize just those results from the three national parks in the Sierra Nevada, Sequoia-Kings Canyon (SEKI) and Yosemite (YOSE).

More pesticides were detected in SEKI than in any other park, and concentrations of current and historic-use pesticides were among the highest for all parks. Values for YOSE were generally somewhat lower. The source of most of these contaminants is believed to be the intensively-agricultural Central Valley, located just upwind. In SEKI, concentrations of the current-use pesticides, chlorpyrifos and dacthal, were particularly high. Samples of lake sediments confirmed that most pesticides first appeared at detectable levels in the 1950s, soon after they were first registered for use in the U.S. Concentrations of historic-use pesticides (e.g., chlordanes and DDT) generally decreased following bans on their use in the U.S. in the 1970s and 1980s, but concentrations of other contaminants (e.g., several current-use pesticides, PCBs) continue to increase. Using "contaminant health thresholds", the study concluded that in some cases concentrations of pesticides and mercury in the nonnative brook trout collected from the SEKI study lakes were high enough that consuming these fish could cause health problems in wildlife and humans.

Reading through the details of all of the contaminants found in the various samples, its easy to forget that the study is reporting results for national parks, those "crown-jewels" set aside from development to provide examples of intact ecosystems. Fulfilling this mission was a lot easier when threats were local (e.g., logging, mining, etc.). In the case of airborne contaminants drifting into our national parks from distant sources, it is clear that the Park Service mission will be increasingly difficult to fulfill. If regulating current-use pesticides within the U.S. isn't enough of a challenge, what does the Park Service do about contaminants originating in even more distant locales (e.g., China)?

After finishing reading the report, I couldn't help but think of that photograph of Earth taken from the moon - that precious blue, green, and white marble floating through the blackness of space. Traditional management boundaries (e.g., countries) will be increasingly irrelevant as we attempt to mitigate impacts generated by industrial societies across the globe. As with greenhouse gases, controlling airborne contaminants will only be possible if we can work across national borders for the benefit of Earth.

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