Foreseeing fires

Abstract

To predict future wildfires, researchers are building models that better account for the vegetation that fans the flames . Wildfire ripped through the black spruce forests of Eagle Plains, Yukon Territory, Canada in 1990. Fire came again in 2005. By the time plant ecologist Carissa Brown arrived in the summer of 2007, all but a few trees were dead. Any seedlings that had sprouted after the first fire had burned in the second. Their charcoaled trunks had disintegrated by 2007, leaving open land furred with swishing grasses and tundra shrubs. “It’s not what you expect to find up there,” says Brown, at Memorial University of Newfoundland in St. John’s, Canada (1). Frequent fires dramatically change patches of the landscape in Eagle Plains, Yukon Territory, Canada. Consider the vegetation in the unburned black spruce forest ( Left ) compared with a stand burned about 100 years ago ( Middle ), compared with one burned in 1990 and 2005 ( Right ). Images credit: Carissa Brown (Memorial University of Newfoundland, St. John’s, NL, Canada). Yukon forests evolved to regenerate quickly after fire. Adult trees died in historical burns every 80 to 150 years, but the heat unsealed the burning trees’ small, resinous cones to drop their seeds, kick-starting the next generation. Seedlings that established in the first five to 10 years after a fire took decades to mature. But now, as the subarctic undergoes rapid warming, some hotter, drier forests are burning much more often, killing immature spruce trees before they have time to set cones. The problem is not limited to the far North. Around the world, wildfires are growing more frequent—as well as larger, hotter, and more destructive (2). Researchers can no longer look to the past as an accurate predictor of the future. Forests adapted to rare fires may not persist through frequent …