By Alicia Chang
The Associated Press

Global warming could stoke ferocious wildfires that will be more difficult and costly to fight and might drastically alter the environment in parts of the world, some scientists warn.

Approximately 1,000 scientists and forestry officials who gathered in San Diego for an international wildfire meeting that began Monday urged policymakers to consider the effects of global warming when managing wildfires.

The wildfire season that just ended in the U.S. was the most severe — and expensive — on record with more than 89,000 fires scorching 9.5 million acres, according to the National Interagency Fire Center. The U.S. Forest Service spent $1.5 billion fighting those fires — about $100 million over budget.

Wildfire season typically peaks in late summer and early fall. Climate change is already being blamed for a longer fire season and some even predict the possibility of a year-round fire season.

"We may need to go to a more permanent work force to manage fires," said Timothy Ingalsbee, executive director of the nonprofit Firefighters United for Safety, Ethics and Ecology.

Future fires, the scientists warned, could drastically alter the land and convert vegetation from one type to another. That, in turn, could put native animals and plants at risk of extinction.

Increased wildfires also could adversely affect the planet. Wildfires emit tons of carbon dioxide into the atmosphere, contributing to planet-warming greenhouse gases.

"We are facing a new reality," said Robin Wills, the president of the Oakland-based Association of Fire Ecology, a professional group.

Battling wildfires has been complicated by thick forest undergrowth and the increasing encroachment of people near forest land.

"You add on climate change and it's going to make things that much worse," said Thomas Swetnam, who heads the Laboratory of Tree-Ring Research at the University of Arizona.

The Forest Service has used a number of techniques since the 1960s to lower the risk of wildfires. One of the most common is prescribed burns that involves intentionally setting fires before and after peak fire season under controlled conditions to reduce undergrowth.

Scientists suggest, among other things, that regions most at risk be targeted for controlled burn programs.

Scientists say an explosion of wildfires will increase fire costs and that old techniques may have little effect in controlling fires.

"With the types of fires that we're going to be seeing, it's not going to be humanly possible to put all of them out," said Ingalsbee.

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On the Net:

International wildfire meeting: http://emmps.wsu.edu/firecongress

National Interagency Fire Center: http://www.nifc.gov/index.html

U.S. Forest Service: http://www.fs.fed.us