Global Warming Causes More Severe Forest Fires

by Stephen Leahy

(IPS) -- New Canadian research shows that forest fires are becoming larger and more intense due to the effects of climate change and are adding enormous amounts of greenhouse gases into the atmosphere.

Fires in the northern hemisphere's boreal forest and peatlands are of particular concern because the region holds 40 percent of the planet's terrestrial carbon. That's almost twice the amount in the world's tropical forests.

The boreal region forms a circumpolar band throughout the northern hemisphere, extending through Russia, Northern Europe, Canada, and Alaska. It is already warmer due to climate change and parts are also getting drier, researchers report.

Significant burning of the boreal forest and peat could produce a positive feedback loop leading to hotter and drier conditions and more area burned, says Brian Stocks, a senior fire research scientist at the Canadian Forest Service (CFS).

"Forests are a wild card" about how fast and how far global temperatures will rise, Stocks said in an interview. "There could be a big disaster ahead."

Fires in Indonesia that raged for months in the late 1990s released an estimated 2.6 billion tons of greenhouse gases, or the equivalent of about 40 percent of world industrial emissions in a year.

As trees grow, they absorb carbon dioxide, the primary greenhouse gas. When a tree rots or burns, the absorbed carbon is released. In the pre-industrial era, there was a rough balance between the carbon released from burning forests and that taken up by new forest growth.

However, burning fossil fuels has liberated large amounts of additional carbon that had been locked away for millions of years in oil, coal and natural gas. This is expected to double the amount of carbon dioxide in the atmosphere in the next 20 to 30 years.

Forest fires could speed that up and lead to a tripling of burned areas, which many scientists believe would be calamitous for many parts of the world.

"Over the last 30 years the area burned in Canadian forest fires has almost tripled," says Mike Flannigan, a researcher at CFS. Increased temperatures, drier conditions and more lightning have also been observed over the same time period. In Canada, fires caused by lightning are responsible for 80 percent of the forest area burned.

"This increase is due to human-cause climate change," Flannigan added.

Eric Kasischke, a fire ecologist at the University of Maryland, agrees that the size of the fires and their intensity has dramatically increased in North America's northern forests.

"Fires in recent years have been two or three times as large as anything ever seen," Kasischke, who has been studying Alaska wildfires for more than 20 years, told IPS.

The fires are outpacing regrowth, and their intensity means that not only the trees are burning but also the understory vegetation and, most importantly of all, the organic matter in the soil.

There is nearly ten times more carbon in the boreal region soil than in the plants and trees above. By contrast, tropical forest soils have one-third the amount of carbon.

"Bad fires in the boreal area consume everything right down to the underlying rock," the ecologist said.

Normally wet peatlands burn when dry conditions lower the water table. Much of Western Canada and parts of Alaska are experiencing increasingly dry conditions, he says. Peat fires can smolder for weeks or even months, releasing large amounts of carbon.

Canada had been counting on its 418 million hectares of forest, 10 percent of the world total, to help meet promises to reduce greenhouse gas emissions under the Kyoto Protocol on climate change.

Whether forests are overall carbon emitters or carbon sinks has been the subject of much debate during the Kyoto negotiations. Many factors are involved, including the age of the forest, growth rates, and composition.

However, there will be more and more fires in the boreal, Kasischke predicts.

"Under current conditions North America's boreal region is no longer a carbon sink," he warned.

A couple of bad fire years, and Canada will be in a big carbon deficit when it comes to making its Kyoto obligations, he says.

Forest fires are not just a problem in Canada, where an average of 2.5 million hectares of forest burn every year. Kasischke and colleagues estimate that more than 12 million hectares of Russian boreal forests burn annually, with 25 million hectares going up in smoke in 2004 alone.

The taiga, as it is known in Russia, represents 80 percent of the world's boreal forest, covering some 12 million square kilometres.

Climate change has increased the average temperatures in the taiga but poor data on past fires makes it impossible to know if the area burned is increasing. Nor is it possible to know how much carbon is being lost. Fortunately, most of the taiga is wetter than its North American counterpart.

Roughly one third of North America's boreal region is becoming more vulnerable to fire, researchers found. Several billion tons of carbon will go up in smoke each decade and there is little that can be done to stop fires in these remote regions, Kasischke says.

This net increase on carbon from the boreal has not yet been fully integrated into the current climate models, he notes.

The next full assessment of this and other new data by the Intergovernmental Panel on Climate Change (IPCC) is not due until 2007. Some scientists acknowledge that the new data means that large rises in temperatures approaching 11 degrees C, once thought impossible, cannot be ruled out.

"This puts enormous emphasis on the need to reduce industrial emissions of carbon," Kasischke says.