This Year’s Wildfires May Change Western Forests Forever—and Not for the Good
Temperature hikes driven by global warming have helped make this summer’s wildfire season in North America one for the history books. Now experts are beginning to wonder if Western forests, which evolved over aeons in a cooler, wetter world to coexist with seasonal fire, may be fundamentally changed as a result.
In Alaska, unusually low snow and rain fall over the winter of 2014–15 combined with remarkably hot spring temperatures in excess of 90 degrees Fahrenheit to create the second-biggest wildfire season on state record. About 8,000 square miles of Alaskan forest were scorched before late summer’s traditional climate cool-down helped firefighters curb the worst burns.
That has allowed Alaska officials to release fire crews to the south, where 66 large fires are burning across 2,500 square miles in several states, including Washington, Oregon, and California, according to Mark Cochrane, a climate scientist at South Dakota State University.
Part of the reason is that American forest managers have suppressed the natural fire ecology cycle for decades, which has allowed an overabundance of deadwood to build up on the forest floor. “These are landscapes that are designed to burn, and if we put them out, we just create a larger problem over time,” Cochrane told reporters Wednesday. “We were successful from 1910 on, and now we’re reaping the whirlwind of that success.”
But even that does not account for the severity or size of wildfires in the West this year and how hard they have become to control, he said.
“We have significant rises in temperatures, drops in relative humidity—which dries fuels—and increases in number of rain-free days,” Cochrane said, along with “higher frequency of high wind years. This is when we can make a significant fire into a large fire,” such as Washington state’s enormous, barely controlled Okanogan Complex fire.
“We are changing fire regimes,” Cochrane added. “We are changing how often things burn now and how intensely,” and the changes will only intensify unless nations slash greenhouse gas pollution.
At current rates of carbon dioxide emissions from burning oil, gas, and coal, climate experts forecast that summers in the Western United States could be more than six degrees hotter by 2100.
“Fires seeming to burn much differently than they did in a natural context,” Park Williams, a climate scientist at the Lamont-Doherty Earth Observatory of Columbia University, told reporters. “We’re seeing these megafires now. Instead of aiding regeneration, they destroy forests entirely. What comes back might not be anything like what we consider the natural state of the forest.”
Recent research led by Williams has shown that natural climate cycles, rather than climate change, are still the dominant cause of the current drought. But human-driven climate change “has increased the area experiencing record-breaking drought by about 45 percent,” he told reporters. “This is important to fire because it seems to react exponentially to drought,” with even a small degree of additional warmth contributing to a much more serious wildfire.
Unusually hot temperatures during the winter of 2014–15 led to a nearly snowless winter in Washington, Oregon, and California. Precipitation fell as rain and flowed out of the mountains and forests instead of building up as snowpack, leaving the region parched, ready to burn, and with few or no extra supplies of water in the backcountry to aid firefighters.
“Where we would see year-round lakes and streams at upper elevations, we know they might not be there now, and we have to adjust our tactics,” said Lou Paulson, president of California Professional Firefighters. “There are big public policy discussions that have to be had, and people in public policy have to realize that this is a new normal going forward.”