LEADING FIRE ECOLOGIST SAYS MORE AND HOTTER FOREST FIRES DUE TO GLOBAL WARMING COULD CAUSE THE LOSS OF HALF THE FORESTS IN THE WEST -- "60 MINUTES"

Global warming will result in more than rising oceans and melting icecaps. According to one of the world's leading fire ecologists, the warming trend is also increasing the intensity and number of forest fires so much that the American West could lose half its forests by the end of the century. Scott Pelley speaks to Tom Swetnam, a fire ecologist at the University of Arizona, for a report on mega-fires to be broadcast on 60 MINUTES, Sunday, Oct. 21 (7:00-8:00 PM, ET/PT) on the CBS Television Network.

"As fires continue to burn - these mega-fires continue to burn - we may see, ultimately, maybe more than half the forest land converting to other types of ecosystems," says Tom Swetnam. "[It will happen] within some decades, to a century, as warming continues and we continue to get large-scale fires," he tells Pelley.

Last year was the worst fire season in recorded history and this season is already second, with eight million acres burned. Average temperatures are up a degree, causing earlier springs and longer fire seasons and quadruple the number of fires. "The fire season in the last 15 years has increased more than two months over the whole Western U.S.," says Swetnam. "So actually 78 days of average longer fire season in the last 15 years compared to the previous 15 or 20."

Tom Boatner, chief of fire operations for the federal government, says he's seen the results up close on the fire line and in the statistics. "We got records going back to 1960 of the acres burned in America. So, that's 47 fire seasons. Seven of the 10 busiest fire seasons have been since 1999," he tells Pelley. The fires are bigger and more frequent. "Ten years ago, if you had a 100,000-acre fire, you were talking about a huge fire....Now we talk about 200,000-acre fires like it's just another day at the office," says Boatner, who says he and his firefighters have battled two fires this year that were over 500,000 acres.

Part of the blame for the fires is a strategic mistake made by the forest service. Throughout most of the 20th century, all forest fires sighted, big and small, were extinguished. This vigilance led to an increase in the amount of fuel in forests. "So now, when the fires get going, there's a lot more to burn than historically you would have seen ," Boatner tells Pelley.

With more to burn, the fires are more intense and all consuming, leaving very little to grow back and scant soil from which it can take nourishment. On a fire-ravished landscape, Swetnam points to the ground. "We used to have forest soil here that might have been this deep," he says, indicating about a foot of depth, "but now we're just down to rock...sort of armored soil and that is not a good habitat for trees to re-establish," he tells Pelley.