University of Wisconsin-Madison forest scientists are heading into Canada to determine how fires in the great boreal forest alter its uptake and release of carbon dioxide. Their findings will help policymakers understand the region”s role in global warming.

Stretching across parts of North America, Europe and Asia, the boreal forest is the second largest forested region in the world, according to Tom Gower, a forest ecologist in the College of Agricultural and Life Sciences. Although the U.S. media largely ignore fires there, they burn an area half the size of Wisconsin on average each year. That”s more than twice the 7.3 million acres that wildfires burned in the United States last year.

Fires from lightning are natural features of the boreal forest, much of which grows atop a peat layer rich in carbon. “When you get up in a plane, what you see is a patchwork of areas that have burned at different times in the past,” Gower says.

Burning coal, oil and gas has increased atmospheric carbon dioxide levels, prompting a global warming trend, according to most scientists. They consider forests a moderating factor because trees remove carbon dioxide from the atmosphere, thus slowing its buildup. The boreal forest plays an especially important role because of its size and the enormous amount of carbon contained in plants and soils there.

“Historically, we”ve thought of this ecosystem as a region that stores carbon,” says Gower. “But if fires become more frequent, all bets are off.

“We know that the boreal region is becoming hotter and drier, and that fires have become more frequent during the past 20 years. Wildfires in boreal forests can be much larger than the fires we experienced in the western U.S. in 2000 because they are often ignored unless they threaten communities.”

Gower says that wildfires burn an area of boreal forest approximately one-half the size of Wisconsin during a typical year. During years when conditions for fires are favorable, wildfires may burn an area almost twice the size of Wisconsin. On a trip to China, Gower saw the remains of a 1987 fire that burned more than 3.2 million acres. In a recent paper, he and his colleagues from the Northeast Forestry University in China estimated that the fire produced 2 percent to 5 percent of the total worldwide carbon dioxide emissions in 1987.

Gower and colleagues at four other institutions have received a 4-year, $3-million grant from the National Science Foundation to examine the effects of wildfires on carbon uptake and release from a series of boreal forest stands located in northern Manitoba.

The researchers will measure carbon exchange in forest stands that burned at different times, and use remote sensing to assess the frequency and extent of fires today. They”ll also employ computer models to predict whether the ecosystem will be absorbing or releasing carbon as temperatures increase and fires become more frequent.

During the past decade, Gower spent five years in Canada and two years in Sweden studying carbon exchange between the boreal ecosystem and the atmosphere. He has enormous respect for the ecosystem”s complexity.

“It”s dangerous to make assumptions about carbon cycling in this environment and predictions about how this will affect global warming. We don”t fully understand the carbon dynamics in forests of different ages in this region and how fires affect carbon budgets,” Gower says.

Boreal soils are often wet and acid. They are a major carbon reserve, and scientists realize they need to know how fires affect the frozen carbon stored there, Gower says. Without a forest cover, the soil surface warms up and melts the permafrost, or frozen soil containing the carbon. This melting can lead to increased bacterial activity and release additional carbon dioxide.

In addition to researchers from the UW-Madison, the group includes scientists from the University of California at Irvine, the University of Alaska at Fairbanks, the Canadian Center for Remote Sensing and the U.S. Geological Survey. The group will coordinate their project with other studies in Siberia and China.