Wildfire Forecast: More Devastating Seasons to Come for U.S.

Wildfire Forecast: More Devastating Seasons to Come for U.S.

 19 September 2006

published by news.nationalgeographic.com

USA — Cold weather brought rain and snow to the Northern Rockies and the Pacific Northwest this week, giving firefighters in Montana, Washington, and Oregon some much-needed relief from an ongoing wildfire season that is headed for the record books.

Since January, when early wildfires swept across Texas and Oklahoma, more than 8.8 million acres (3.5 million hectares) of forest and grasslands have been scorched in the western United States, according to the National Interagency Fire Center (NIFC).

That’s an area twice the size of New Jersey.

The amount of acreage burned tops any since 1960, when officials started collecting reliable tallies of fire damage, and is far higher than the ten-year average of 4.9 million acres (1.9 million hectares) a year.

“We had a lot of large fires this year,” said Rose Davis, spokesperson for the NIFC in Boise, Idaho.

“We had drought conditions and, up to this weekend, we didn’t get a lot of breaks as far as the weather goes.”

At one point, firefighting resources were stretched so thin that U.S. officials enlisted the help of nearly a hundred firefighters from Australia and New Zealand.

Canadian firefighters also helped along the U.S.-Canada border, where planes dropped fire-retardant slurry on the flames.

More Fires May Be the Norm

A pair of new studies suggests that huge wildfire seasons like this year’s may become the norm in the western United States, as global temperatures continue to climb and the drought conditions that have turned the region into a virtual tinderbox worsen.

“The western United States is getting warmer,” said Thomas Swetnam, professor of dendrochronology at the University of Arizona in Tucson and the author of a study published last month in the journal Science. 

“With this continued trend of warming, we are going to see more big fires.”

Swetnam’s study concludes that climate change has lengthened the average wildfire season by 78 days and the average duration of large fires from 7.5 days to 37.1 days.

The Rocky Mountains are experiencing most of the climate-influenced wildfires, Swetnam adds.

Snowmelts there are occurring earlier because of higher temperatures, giving grasses and trees longer to dry out and create fuel for summer lightning strikes, he explains.

Likewise, research published this summer in the journal Conservation Biology concludes that the West should brace for even heavier wildfire seasons in the future.

According to Donald McKenzie of the U.S. Forest Service’s Pacific Wildland Fire Science Lab, the area burned by wildfires in 11 Western states could double by 2100 if summer temperatures climb by 1.6 degrees Fahrenheit (0.9 degree Celsius).

Wildfires Always Unpredictable

Swetnam notes that although wildfires may continue to trend upward, there will likely be tremendous variability from year to year.

And even if the perfect conditions for wildfires exist, the fires may not necessarily come.

Both Arizona and New Mexico seemed ripe for major wildfires this year after an exceptionally dry winter that brought little snowpack to the mountains.

(Read related story: “Drought Causing Record Forest Destruction in U.S. Southwest.”)

But those states were spared when record-breaking monsoons brought heavy summer rains instead of the fierce fires officials had expected.

Now fire officials in those states have a new worry: Summer rain might bring more grass that will become fodder for fire in the years to come.

As U.S. Park Service meteorologist Rich Naden notes, one lucky season doesn’t change the long-term fire outlook in the Southwest.

“It’s just a matter of time here,” he said.

That sentiment is being echoed all over the West, where state, federal, and local governments have stepped up prescribed burns and strategic forest thinning to reduce potential fire fuel in critical regions.

(Watch related video: “Giant Fire Lit to Save Northern U.S. Forest.”)

Some communities in the Rockies are spraying forests where bark beetle infestations are killing trees in huge numbers and creating vast swaths of dead wood, said Jim Maxwell, spokesperson for the U.S. Forest Service.

“It’s like trying to stop a hurricane,” Maxwell said. “But everywhere, federal, state, and local officials are getting their heads and their money together to identify what they can protect.”

An Upside and a Downside

Wildfires also provide certain benefits, Maxwell notes.

He observes that some forests that have been badly damaged by recent fires appear to be regenerating and may be healthier than they were before.

The University of Arizona’s Swetnam agrees. “Fire can be a good thing because it does restoration work,” he said. “But where you get high-severity fire in big patches where it hasn’t happened before, entire habitats can be wiped out.”

Fires can have different effects in different kinds of forests, he explains. Some species, like lodgepole pine, require extreme heat to release their seeds and therefore need fire in order to regenerate.

But other species, like ponderosa pine, are accustomed only to low-severity fire and may not grow back after an intense blaze.

McKenzie, of the U.S. Forest Service, warns in his study that extensive habitat damage caused by large wildfires may push some threatened species to the brink of extinction.

Two years ago, for instance, the forest atop Mount Graham near Safford, Arizona, caught fire and nearly wiped out habitat containing 18 species found nowhere else in the world.

Swetnam points out that the forests of the Northern Rockies, where large fires occur only once every 100 to 300 years, may prove vulnerable to a revved-up fire cycle.

“[The forests] are very likely to change to something else as they burn more often,” he said.


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