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Climate Change Is Making It Harder for Forests to Recover From Wildfires

A growing body of research suggests that, thanks to various environmental symptoms of climate change, America's forests are increasingly at a disadvantage when it comes to recovering from devastating wildfires.
Flames from the Camp Fire burn near a home atop a ridge near Big Bend, California, on November 10th, 2018.

Flames from the Camp Fire burn near a home atop a ridge near Big Bend, California, on November 10th, 2018. America's forests are increasingly at a disadvantage when it comes to recovering from devastating wildfires.

After consuming more than 153,000 acres, including nearly 14,000 residences, and accounting for 88 fatalities, the Camp Fire has finally been contained. But while communities can now commit fully to recovering from the catastrophic blaze, the landscape itself may have a harder time doing so. Blame climate change.

A growing body of research suggests that, thanks to various environmental symptoms of climate change, America's forests are increasingly at a disadvantage when it comes to recovering from devastating wildfires. A survey of 52 blazes across 1,485 locations in the Rockies, published earlier this year in Ecology Letters, found that warming temperatures enhance moisture stress on plants, which in turn dramatically inhibits post-wildfire tree growth.

The survey revealed "significant decreases in tree regeneration in the 21st century," wrote the research team, led by assistant professor Camille Stevens-Rumann. "Annual moisture deficits were significantly greater from 2000 to 2015 as compared to 1985 to 1999, suggesting increasingly unfavorable post-fire growing conditions, corresponding to significantly lower seedling densities and increased regeneration failure." This isn't an issue of rainfall, but outright soil moisture, which The Atlantic reported in August is at its lowest level in years in many western parts of the United States. Drier soil means more fuel, which means a landscape that scores low for "resiliency," the ecological term referring to a system's ability to recover and adapt to volatile climate—in this case, major conflagrations.

Resiliency can be a difficult area for policymakers to rally around. It's an abstract threat that requires long-term data and modeling—two elements that often lack the visceral punch of, say, flooded subways after Hurricane Sandy or smoldering homes after the Camp Fire; indeed, it took major climate events like Sandy for cities like New York City to start taking resiliency seriously as a matter of public policy. But that doesn't make programs like forest restoration any less important.

"Loss of vegetation as a result of an intensely burning large fire can expose soil to erosion," the National Forest Foundation, a non-profit that works with the U.S. Forest Service, noted in 2015. "Following such a fire, storm events or spring runoff on denuded slopes can cause ravaging floods and debris flows, which may damage structures, roads, trails, water reservoirs, put community water supplies at risk, and harm critical wildlife habitat. These adverse impacts can continue to occur for years after the fires are extinguished"—in other words, a catastrophic, and irreversible, degradation of forests beyond their ability to naturally regenerate.

While naturally occurring forest fires have played an integral role in the life cycle of various ecosystems, forest ecosystems simply don't grow back the way they used to—a problem that will only escalate exponentially in the future. "Dry forests that already occur at the edge of their climatic tolerance are most prone to conversion to non-forests after wildfires," Stevens-Rumann and her colleagues wrote. "Major climate-induced reduction in forest density and extent has important consequences for a myriad of ecosystem services now and in the future."

This, in turn, limits a key mechanism for forest resiliency and restoration: controlled or "prescribed" burns, the kinds designed to deprive fast-moving fires of fuel. According to the most recent data from the National Association of State Foresters, 11.7 million acres of U.S. soil were treated with prescribed fire in 2014, and states are increasingly embracing the strategy as a central component of their land management strategy; the number of states offering prescribed burn education jumped to 24 between 2012 and 2015—a 41 percent increase, per the NASF report.

But where prescribed burns were once a useful tool, climate change-induced fragility makes them too blunt an instrument for building forest resiliency. A study published in March by the Ecological Society of America found that controlled burns that often occur naturally under policymakers' watch "can improve forest resilience and contribute to restoration efforts in fire‐adapted forests," the tradeoffs—wildlife habitat, smoke, and general human peril among them—aren't worth a potential restoration that's "unlikely to have a significant impact on the occurrence of high‐severity wildfires."

When it comes to forest management, environmental managers can no longer rely on fighting fire with fire.