Climate Change Linked to Giant Spike in Forest Fires

Researchers find that the number of acres burned has doubled as temperatures have risen, destroying wildlife habitat and harming human health.

(Photo: U.S. Forest Service/Corbis via Getty Images)

Oct 12, 2016· 2 MIN READ

David Kirby has been a professional journalist for 25 years. His third book, Death at Seaworld, was published in 2012.

It’s not your imagination: Wildfires are spreading, and climate change is to blame.

A new study has found that climate change from human activity nearly doubled the area burned by forest fires over the past three decades in the Western United States.

“We estimate that human-caused climate change contributed to an additional 4.2 million hectares of forest fire area during 1984–2015,” the authors wrote in the journal Proceedings of the National Academy of Sciences. That’s 16,200 square miles, roughly the size of Massachusetts and Connecticut combined.

Increased forest fires have ripple effects that include destruction of wildlife habitat, respiratory illnesses in humans from smoke, rising carbon dioxide emissions, soil erosion, and more public spending on firefighting.

Research has linked climate change to the jump forest fires, but the new study is the first to quantify that relation, said coauthor Park Williams, a bioclimatologist at Columbia University’s Lamont-Doherty Earth Observatory.

Average temperatures in Western U.S. forests have risen by about 2.5 degrees Fahrenheit since 1970 and are expected to keep climbing. Rising temperatures increase the dryness of brush, according to the study, which in turn increases the risk of forest fires. Other factors include natural fire suppression measures that allow for excess fuel growth, human settlement, and natural climate variability.

The researchers found that between 2000 and 2015, climate change caused 75 percent more forested area to experience high fire-season fuel aridity and an average of nine additional days per year of high fire potential.

“We were surprised by what a strong relationship there was between the dryness of the climate, which is affected by temperatures, and the area of Western forest that was burned,” Williams said.

“Even though there are a lot of things that affect fire, this one variable, the dryness of the environment, accounts for almost all of the changes in forest fire area over the last 32 years,” he added.

Tinderbox conditions are not the only climate change factor affecting forest fires. Reduced snowpack, for example, could be affecting soil moisture, and rising temperatures might increase lightning strikes, igniting more fires.

Other factors not included in the study were vegetation growth possibly caused by rising carbon dioxide levels, vegetation killed by drought, and millions of dead trees as a result of infestation by beetles that flourish in warmer weather.

As temperatures rise, the situation will grow more dire.

“The growing influence [of human-caused climate change] on fuel aridity is projected to increasingly promote wildfire potential across Western U.S. forests in the coming decades and pose threats to ecosystems, the carbon budget, human health, and fire suppression budgets,” the study said.

How bad will things get? Forest fires will burn hotter and longer—until there are no more large swaths of forest to burn, Williams said. Until then, “it seems like as long as the Earth keeps warming, at least for the next couple of decades, we’re going to continue to see big increases in fire.”

There is some cause for hope.

“Warming is going to continue happening no matter what, and that means that increased forest fire areas in the Western U.S. are going to continue happening no matter what,” Williams said. “But if we do manage to adhere to the Paris agreement [on greenhouse gas emissions] and the globe does start emitting less CO2 into the atmosphere, then the relative effects will be reduced.”