October 28, 2008

Amphibian Decline Found In Yellowstone Linked To Climate Change

A new study found that amphibian populations at Yellowstone National Park are in steep decline.

Researchers point to climate change, which is causing the wetlands where animals breed and live to dry out.

The park, which stretches over 9,000 sq km in the western U.S., shares land in Wyoming, Montana and Idaho. U.S. congress granted Yellowstone national park status on 1 March 1872.

The park's vast forests and grasslands are also home to grizzly bears, wolves and bison.

However, all eyes are on the park's amphibians - frogs, toads and salamanders - that for early indications of environment degradation.

The park has four native amphibians: the blotched tiger salamander (Ambystoma tigrinum melanostictum), the boreal chorus frog (Pseudacris triseriata maculata), the Columbia spotted frog (Rana luteiventris) and the boreal toad (Bufo boreas boreas).

The lower Lamar Valley in northern Yellowstone harbors countless small, fishless "kettle" ponds, which are re-filled in spring by groundwater and snow melt. These ponds are the ideal location for amphibian breeding and larval development.

Scientists studied 46 of these "kettle" ponds in 1992 and 1993. Then, between 2006 and 2008, researchers from Stanford University in California repeated the survey and found that the number of permanently dry ponds had increased four-fold.

Additionally, the remaining ponds showed declining numbers of amphibians. Three of the four native amphibian species had suffered major declines in numbers. The number of species found in each location - the "species richness" - had also dropped off markedly.

"They go through an aquatic period and a terrestrial period during their lives so they are very susceptible to changes in both types of environment," said co-author Sarah McMenamin, from the department of ecology and evolution at Stanford.

What's more, McMenamin and colleagues Elizabeth Hadly and Christopher Wright, also found evidence pointing to a drought.

By gauging the monthly temperature and precipitation data from Yellowstone, as well as satellite images of the park taken between 1988 and 2008, researchers found decreasing levels of rainfall and increasing temperatures during the warmest months of the year.

"There is a pretty substantial signal of climate change in this region," said McMenamin.

"Snow pack during the winter is decreasing - which other studies have documented - and the regional aquifer is drying up as a result of these large-scale climate changes.

"These ponds are changing, the environment is changing, the landscape is drying up and the amphibians no longer have a place to breed. It's disturbing."

Climate change might affect amphibian populations in numerous ways. In addition to drying out aquatic breeding habitats - preventing spawning - it could also make the land environment inhospitable to them.

Image Courtesy Wikipedia


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