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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