Boreal lakes surprising resilient to forest fires

By Marie Thoms, UAF Institute of Arctic Biology

A serendipitous study of lake ecosystems in the Yukon Flats National Wildlife Refuge of Alaska, one of the most flammable boreal regions in North America, showed unexpected resilience to forest fires according to a study to be published in the journal Ecology.

Boreal wetlands and lakes account for approximately 50 percent of global lake surface area and are internationally important bird areas, annually supporting more than 15 million breeding water birds in North America. Nonetheless, little is known of fire impacts on boreal lakes, especially those impacts on aquatic food webs.

Smoke from a wildfire in the Yukon Flats National Wildlife Refuge is seen near a study lake in summer 2010. The lake was part of a research project by UAF graduate student Tyler Lewis. (Photo by Mark Lindberg)

“Fire is a major issue for refuge managers in the boreal forest and if you asked them what’s the effect of fire on waterfowl, they probably wouldn’t know,” said Tyler Lewis, a biology and wildlife graduate student at the University of Alaska Fairbanks, who was studying the effects of lake drying on water birds in the Yukon Flats when a series of wildfires erupted close to his study sites.

“The fire was devastating around our study lakes,” Lewis said. “You could see run-off going into the lakes and it only seemed natural that something would change.”

Although his original project had nothing to do with fire, he couldn’t pass up an opportunity to study the exact same landscape and multiple parts of the food web before and after a natural fire.

What Lewis found surprised him. He examined the nutrients, insects and water birds of his study lakes and found surprisingly few effects from the fire. His results are the first known data describing effects of a forest fire on multiple levels of boreal lake ecosystems.

“Overall, our study lakes were largely resistant to forest fire,” Lewis said.

The resilience of the Yukon Flat’s lakes is good news for land managers.

“If you are managing for high-quality wetlands and a fire goes through it, yet the quality of that wetland doesn’t change much, then your conservation planning doesn’t have to include fire as a consideration,” said Mark Lindberg, a population ecologist with the UAF Institute of Arctic Biology who specializes in waterfowl and is Lewis’ adviser.

During the 2000s, the annual area of boreal forest burned in Alaska was 50 percent higher than in any decade since 1940, due to an increased number of years with extensive fires. The frequency and intensity of fires are expected to increase as the climate warms.