Long, hot summers might spell the end for amphibians

Pikas and ptarmigans inspire more public sympathy, but frogs might have an even tougher time with climate change.

As summers get longer and hotter in the next few decades, scientists say some of Mount Rainier’s smaller ponds and wetlands will dry up.

That means amphibian species such as the Cascades frog — already threatened — could be squeezed out of their breeding sites.

The Cascades frog has coloring that roughly resembles an overripe banana. They measure about 2 1/2 inches in length and can live for as long as seven years. Male Cascades frogs are distinctive for the low chuckling sounds they make during mating season.

Cascades frogs are found in only three states — Washington, Oregon and California — and they are narrowly adapted to high, subalpine conditions.

Because their larvae can’t survive through the winter, they’re restricted to developing in a single summer season.

“They are one of the most sensitive resources we have,” Mount Rainier National Park biologist Barbara Samora said. “They’re dependent on surface water bodies for breeding areas. If they don’t have them, their populations will decline.”

If Cascades frogs go extinct, that would be a great loss, Samora said. But their significance goes far beyond that.

Because frogs and other amphibians live both in the water and on land and because they are super-sensitive to changes in environmental conditions, they make excellent barometers of an ecosystem’s overall health.

Though they keep a low profile, amphibians make up a major portion of animal biomass in many habitats. In some forested areas, amphibians exceed the combined weight of all other vertebrates.

Their population declines have an outsize effect on the larger ecosystem because not only are they a food source for many other animals, they also eat algae and countless insects, which helps keep aquatic habitats in balance.

Cascades frogs already are squeezed because of a well-meaning mistake fishing enthusiasts made more than 100 years ago.

Thinking they were doing a good deed, fishermen carried nonnative trout to Rainier’s high lakes in canvas bags filled with water beginning in the 1890s. Wildlife managers continued the practice, stocking Mount Rainier’s lakes and others throughout the Cascade range with nonnative trout that happened to be voracious feeders that gobbled up all the frog larvae and drove them to smaller, marginal ponds.

Already hurting for suitable habitat, the frogs might be pushed to extinction by the increased stress of climate change, said researcher Amanda Kissel at Simon Fraser University in Vancouver, B.C.

Kissel and colleagues, including Maureen Ryan from the University of Washington, are working at Mount Rainier to predict what might happen to specific wetlands under various climate change scenarios so managers will better understand how to deal with the problem.

Their work includes tagging frogs with transponders and using remote sensors to track temperature and water content in soil.

They also are using new computer modeling techniques that analyze digital imagery to identify wetlands and classify them by characteristics.

Their work could have broader usefulness.

“This is an important test case for assessing the potential for climate mitigation strategies,” Kissel said.

Among the options for the frogs: Remove the nonnative fish in lakes and try to make the ponds more amphibian friendly.

Removing the fish would be labor intensive, expensive and controversial. Gill netting is a possibility, but studies in Sequoia National Park and North Cascades National Park indicate it would require netting once a year for as long as eight years.

Killing the fish with poisons, such as rotenone, which occurs naturally in the seeds and stems of some plants, is another option. But rotenone also is toxic to immature amphibians and has negative effects that can last years.

Such drastic measures horrify many environmentalists and national park managers, who traditionally have tried to keep a hands-off approach when dealing with natural processes.

“Taking proactive action is scary,” Samora said. “But if you don’t take any action, it could be just as scary.”

“It’s baby steps right now — as it should be,” she said, “because we don’t want to make mistakes.”