In this video by The YEARS Project, leading ecologist Tom Swetnam sheds light on future fires by looking into the past. Swetnam uses dendrochronology, the use of tree rings to reconstruct and evaluate variations in past and present environments, to study the natural and cultural disturbances of forest ecosystems.

Tree rings are like time capsules. Each ring tells the story of a year in the tree’s life.

“Very small, narrow ring –drought year.
Big fat, thick ring –wet year.”

–Tom Swetnam

Tom examines tree rings along with scars in fire-scarred trees to learn how fires have responded to climate changes in the past. Once Tom knows how climate affected trees in the past, he can then extrapolate how the environment will affect future fires.

“We began to see these really large high-severity fires beginning in the ’70s and ’80s–fires that were like more than 10,000, more than 20,000 acres. Then suddenly, in the late ’80s, we started seeing fires routinely in that size range. And then, since the droughts of 2000, 100,000-acre fires, 400,000-acre fires. Just last year, 500,000-acre fire.”

–Tom Swetnam

Swetnam discovered the following:
•Fires in the American West are now six times more destructive than they were just forty years ago
•Fire season is now nearly four months longer than it used to be.
•Some of today’s fires burn so hotly that they destroy the soil, preventing trees from growing back for thousands of years.

“The smoking gun is basically there. It’s getting hotter, getting dryer, and the fires are going right up along with that.”

–Tom Swetnam

Trees store vast amounts of carbon. When trees burn, the stored carbon releases into the atmosphere and further warms the climate. The warmer the climate, the higher the chance for monster fires.

“This is outside of the norm. To burn every living tree for five miles around. This is catastrophic. We’re starting to see fire behaving in ways that nobody has ever seen before. From our knowledge, with tree ring records and old historic photographs and old pioneer accounts, in these landscapes there’s just no evidence of huge fires burning big holes like that in these places anytime.”

“I really doubt that this place is coming back to forest for many, many, many lifetimes. So, if this continues for the next 20, 30, 50 years, probably could lose 50 percent of our forests.”

“And when we know that we have been the cause of this or at least a large part of the cause of this, then the responsibility, the feeling of responsibility, is even greater to do something.”

–Tom Swetnam