Blazes like last year's Whitewater Baldy Complex fire in New Mexico could make that part of the country inhospitable to trees.
Gila National Forest
Last year's Whitewater Baldy Complex fire was the largest in New Mexico's history, but we can expect worse to come.

The fire that burned through Forest Canyon, a breathtaking stretch of wilderness ringed by snowy peaks in Rocky Mountain National Park, Colo., started in October and burned long past the end of the fire season. Trees still smoldered in late December, and the smoke mixed with dry snow blowing in the air. Known as the Fern Lake Fire, the blaze tore through 3,500 acres of land the federal government set aside a century ago both to provide public enjoyment and protect it from human destruction.

One of those missions has been accomplished: 3.1 million people visit the park each year. Increasingly, however, the destruction it was meant to prevent is encroaching. Like most wildfires, the Fern Lake Fire was the work of careless individuals. Most likely campers let an illegal campfire get out of control. But science suggests our collective effort may have made it much worse.

Last year was the hottest on record in the United States, and the fall weather was unseasonably warm in the Rockies. The forest was weakened by prolonged drought; that November was the driest ever recorded in the park. An epidemic of bark beetles, which thrive in warmer conditions, was already in the process of killing off thousands of trees. The area's first heavy snow came unusually late, in mid-December, and only then did the fire slow down.

Jason Sibold, a geographer who studies forest fires at Colorado State University and who has spent time exploring the canyon where the fire started, says scientists can't say for sure that global warming was a direct cause. Pinning one extreme event to climate change is impossible to do. "But that Forest Canyon site, I never thought I was going to see that burn, much less in December," he said. "That's just shocking."