Amphibians are widely recognized as an indicator of ecological conditions, and the current worldwide declines in amphibian populations reflect widespread environmental degradation. Indeed, climate change is decimating once-common amphibian species in some of the world’s most pristine ecosystems, both directly, through desiccation of wetland habitat, and indirectly through changes in population dynamics and disease. We are interested in the amphibian community in the heterogeneous environment of northern Yellowstone National Park, Wyoming USA. In order to document regional climatic changes, we analyzed temperature and precipitation records recorded at Tower Falls, Slough Creek over the past 60 years. Using surveys of the region performed in the early 1990s as a baseline, we re-surveyed the area for wetland conditions and amphibian population presence. In order to describe long-term changes in wetland presence, we used remote-sensing techniques to analyze Landsat TM satellite images for wetland probability over the last several decades.
Results/Conclusions
Recent climatic change and other factors are causing severe population declines in Yellowstone amphibian populations. We documented severe, significant population extirpations of all four native amphibians, blotched tiger salamander (Ambystoma tigrinum melanostictum), boreal chorus frog (Pseudacris triseriata maculata), Colombia spotted frog (Rana luteiventris) and boreal toad (Bufo boreas boreas). Multiple decades of climatic data showed significant changes in climatic conditions, with decreasing year-round precipitation and increasing temperature during the hottest seasons. Surveys of 49 current and historic bodies of water indicate that these desiccating conditions and increasing temperatures are causing former wetlands to disappear. Over the past 15 years, more than half the pond environments in northern Yellowstone have vanished, and remote sensing analyses further indicate that wetland prevalence is severely declining. Entire amphibian populations have been eradicated from locations that no longer sustain water, and have disappeared even from wetlands that remain hydrated. Even in these hydrated potential habitats, our surveys show that amphibian diversity is at a critical low. Our results indicate that climate change has already disrupted ecosystems in the most protected reserves of our planet, and that current predictions of species vulnerability may not reflect potential impacts of global warming.
