Dried-up ponds are bad news for mountain frogs

"We've seen that the lack of winter snowpack and high summer temperatures have resulted in massive breeding failures and the death of some adult frogs," says Wendy Palen. "More years like 2015 do not bode well for the frogs." (Credit: Richard Droker/Flickr)

The long summer drought in the Pacific Northwest is doing more than causing raging wildfires in Washington state forests.

A less noticeable consequence is taking place in mountain ponds as the drought and minimal snowpack combine to rob the region’s amphibians of their mountain pond habitats.

Further, the summer’s severe conditions may be the new normal within just a few decades, experts warn.

“This year is an analog for the 2070s in terms of the conditions of the ponds in response to climate,” says Se-Yeun Lee, research scientist at University of Washington’s Climate Impacts Group and one of the lead authors of a new study. Current conditions provide a preview of how that will play out.

“We’ve seen that the lack of winter snowpack and high summer temperatures have resulted in massive breeding failures and the death of some adult frogs,” says coauthor Wendy Palen, associate professor at Canada’s Simon Fraser University who has for many years studied mountain amphibians in the Pacific Northwest. “More years like 2015 do not bode well for the frogs.”

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Mountain ponds are oases in the otherwise harsh alpine environment. Brilliant green patches amid the rocks and heather, the ponds are breeding grounds for Cascades frogs, toads, newts, and several other salamanders, and watering holes for species ranging from shrews to mountain lions. They are also the cafeterias of the alpine for birds, snakes and mammals that feed on the invertebrates and amphibians that breed in high-altitude ponds.

For a new study published in the journal PLOS ONE, researchers developed a new model that forecasts changes to four different types of these ecosystems: ephemeral, intermediate, perennial, and permanent wetlands.

Jesters of the alpine

The findings show that climate-induced reductions in snowpack, increased evaporation rates, longer summer droughts, and other factors will likely lead to the loss or rapid drying of many of these small but ecologically important wetlands.

More than half of the intermediate wetlands are projected to convert to fast-drying ephemeral wetlands by the year 2080. The most vulnerable ponds are the same ones that now provide the best habitat for frogs and salamanders.

At risk are unique species such as the Cascades frog, which is currently being evaluated for listing under the Endangered Species Act. Found only at high elevations in Washington, Oregon, and California, Cascades frogs can live for more than 20 years and can survive under tens of feet of snow. During the mating season, just after ponds thaw, the males make chuckling sounds to attract females.

“They are the natural jesters of the alpine, incredibly tough but incredibly funny and charismatic,” says Maureen Ryan, the other lead author, a former UW postdoctoral researcher who is now a senior scientist with Conservation Science Partners.

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The team adapted methods developed for forecasting the effects of climate change on mountain streams. Wetlands usually receive little attention since they are smaller and often out of sight. Yet despite their hidden nature, ponds and wetlands are globally important ecosystems that help store water and carbon, filter pollution, convert nutrients, and provide food and habitat to a huge range of migratory and resident species. Their sheer numbers—in the tens of thousands across the Pacific Northwest mountain ranges—make them ecologically significant.

“It’s hard to truly quantify the effects of losing these ponds because they provide so many services and resources to so many species, including us,” Ryan says. “Many people have predicted that they are especially vulnerable to climate change. Our study shows that these concerns are warranted.”

Land managers can use the study’s maps to prepare for climate change. For example, Ryan and coauthors are working with North Cascades National Park, where park biologists are using the wetland projections to evaluate and update priorities for managing introduced fish and restoring natural alpine lake habitat.

Other researchers from University of Washington and from the University of Notre Dame are coauthors of the study. The Department of the Interior’s Northwest Climate Science Center, the David H. Smith Conservation Research Fellowship Program, and the US Fish and Wildlife Service’s North Pacific Landscape Conservation Cooperative funded the work.

Source: University of Washington