Report: Wildfire risks around the world likely to change dramatically

Wildfire risks around the world are likely to change dramatically during the latter half of this century, with some types of terrain projected to see dramatic increases in likelihood and in the expanse of fire-prone areas during the next 30 years, according to a new study.

The areas at highest risk for increased fires in the short term include landscapes familiar to residents of the western United States – Mediterranean forests, woods, and scrub, such as those that blanket the coastal ranges of California, alpine grass and shrublands, desert shrublands, and forests dominated by conifers.

But over the longer term, significant increases in fire frequency are expected over a much wider range of ecosystems – as are significant decreases.  

IN PICTURES: Colorado wildfires  

Indeed, decreases in fire frequency often take a back seat to efforts to project places where fires are likely to increase. Yet the declines can be just as important, suggests Max Moritz, a fire ecologist at the University of California, Berkeley and the lead author of the study, which was published this month in the journal Ecosphere.

"You're worried about the right kind of fire being maintained or restored in these systems," he says. "Big decrease in fires … could be just as disruptive ecologically as a big increase."

For instance, the decreases could allow vegetation types alien to the existing landscape to move in and alter the region's ecology in unpredictable ways. Or fewer fires would allow fuels to build up to levels that allow the fires that finally occur to reach catastrophic levels.

One type of ecosystem projected for significant decreases by century's end are subtropical savannas in Africa, Australia, and elsewhere. These are projected to see fewer fires than they currently experience, the research suggests. This would lead to major ecological changes there, since frequent fires keep savannas savanna-like.

Previous studies largely have produced projections of changing fire risks for individual regions of the globe, such as the western US. This new study is a rare attempt at trying to gauge future changes to wildfire patterns globally as the climate warms, the research team says. The warming has been triggered and sustained by rising carbon dioxide concentrations in the atmosphere, increases researchers have traced to burning fossil fuels as well as by land-use changes.

The study applies to fires once the province of ecologists trying to gauge the effect of climate change on the future distribution of plants and animals, Dr. Moritz explains. It treats fire as an entity that has its own form of ecological requirements: fuel, fire-favorable climate patterns, and ready sources of ignition.

The researchers first gathered global wildfire data gathered by two satellites and spanning 11 years – from 1997 to 2007. They used the information to estimate wildfire probabilities for each of 14 different broad vegetations types, or biomes, around the world under climate conditions that existed at the time.

They then turned to 16 climate models to develop projections of the climate's likely trajectory. They applied the results from each climate model to their fire model separately to see how much convergence they might or might not show in the final results.

They also used an existing model for plant production as a way to see how the abundance of fuel for these biomes could change in a warming climate.

As for ignition sources, the third piece of a fire's "ecosystem," humans supply the latter with enough regularity to suggest ignition sources won't be a limiting factor for fires.

From these steps they estimated changes to fire risks for each of the biomes for two periods: a 30-year span starting in 2010, and another starting in 2070.      

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