WASHINGTON — Snow hardly fell during winter in snowy Colorado. On top of that, the state’s soaking spring rains did not come. So it was no wonder that normally emerald landscapes were parched as summer approached, tan as a pair of worn khakis.
All the earth needed was a spark.
Colorado and U.S. Forest Service firefighters are battling the state’s most destructive wildfires ever. Lightning and suspected arson ignited them four weeks ago, but scientists and federal officials say the table was set by a culprit that will probably contribute to bigger and more frequent wildfires for years to come: climate change.
In the past two years, record-breaking wildfires have burned in the West — New Mexico experienced its worst-ever wildfire, Arizona suffered its largest burn and Texas last year fought the most fires in recorded history. From Mississippi to the Ohio Valley, temperatures are topping record highs and the land is thirsty.
“We’ve had record fires in 10 states in the last decade, most of them in the West,” said U.S. Agriculture Undersecretary Harris Sherman, who oversees the U.S. Forest Service.
Over the past 10 years, the wildfire season, which normally runs from June to September, expanded to include May and October. Once, it was rare to see 5 million cumulative acres burn in a year, but some recent seasons have recorded twice that.
“The climate is changing, and these fires are a very strong indicator of that,” Sherman said.
A study published last month in Ecosphere, a peer-reviewed journal of the Ecological Society of America, projected that most of North America and much of Europe will witness a jump in the frequency of wildfires by the end of the century, mostly because of increasing temperatures.
“In the long run, we found what most fear: increasing fire activity across large parts of the planet,” said Max Moritz, a lead author of the study and fire specialist at the University of California Cooperative Extension.
Scientists say they do not have the data to link climate change to Colorado’s decreased snow and rain. But climate change has been linked to higher temperatures that cause snow to melt earlier and rain to evaporate faster, parching the land, contributing to drought and drying out the vegetation that can fuel fires, said John Nielsen-Gammon, the Texas State climatologist.
Under such conditions, snow and rain can fall at the same rate as before, but the drier earth is slower to revive.
In Colorado’s warmer climate, a plague of pine beetles has thrived. Without extremely cold winters that reduce their numbers, the beetles breed twice per year instead of once. They nibble trees until they die, leaving millions of acres of potential firewood.
The High Park fire west of Fort Collins, where 33,000 residents were evacuated, is feeding on forest filled with trees eaten by beetles.
From March to May, most of Colorado had less than half the usual precipitation, and some areas had almost no rain or snow, said Nolan Doesken, director of the Colorado Climate Center at Colorado State University.
No one predicted fires like the current ones, but years ago, climate scientists warned state and federal officials that they could start seeing early springs, more hot and dry weather, and frequent and perhaps severe droughts, Doesken said.
The National Center for Atmospheric Research in Boulder was among the first to sound an alarm.
Climate scientists there saw temperatures rising nationwide. Rain cycles changed from mild and prolonged to hard and short. During the longer dry spells in between, land was susceptible to burns, said Bob Henson, meteorologist and science writer at the National Center for Atmospheric Research in Boulder.
Colorado is in the middle of “a terrible dry period,” Henson said. The snowpack statewide was less than 3 percent of normal on June 1, about the time the fires started.
With a warming climate, authorities are going to need to be more active in managing forests to limit wildfire damage, scientists say.
In New Mexico, where two fires recently combined to form the Whitewater-Baldy Complex, the state’s largest-ever wildfire, Christopher Allison sees other disastrous fires waiting to happen because, he said, the Forest Service has not allowed loggers to clear trees.
“I think you’re going to have to get in there … and remove trees,” said Allison, department director for extension animal sciences and natural resources at New Mexico State University. “There are millions of acres that look a lot like what’s being burned right now.”
Clearing trees is important because fires like to climb. A low-intensity burn that starts in grass will work its way up small trees. Fires burn with higher intensity in the canopy, where they are harder to manage, Allison said.
Logging is forbidden in some Western areas to protect the endangered Mexican spotted owl. But the Forest Service must make a call — wildfire or the owls, Allison said.
Another problem is the construction of homes next to scrub brush that often is a starting point for fires. “It’s not a matter of if they burn, but when,” Allison said.
About one in four Colorado homes sits in a fire risk zone, a recent state report showed — involving about a million people, according to a Colorado State Parks map.
Sherman said the Forest Service is working to clear forests of the food that fires need to grow. The agency oversees 193 million acres, and as much as 82 million acres need to have dead trees and grass removed, he said.
A controlled burn is one method, costing $200 per acre, money the Forest Service does not have, he said. Logging is another way, but as the price of lumber has been falling, many sawmills say removing trees is not worth the expense.
So the Forest Service has set modest goals. In 2004, it worked to clear its woods of 2.1 billion board feet of trees, the measurement of cut trees from top to bottom. The 2012 goal is 2.6 billion, about 215,000 acres, Allison said.
“These are the areas where we have our greatest difficulty in protecting life and property,” Sherman said. “When you’re talking about vast forest … it’s very difficult.”