Wildfires accelerating tree migration from climate change: study

Migrant trees are finding new homes in forests across the Western U.S., as changing climate conditions — accelerated by wildfires — force them to seek out cooler, wetter locations, a new study has found.

The research, published on Monday in Nature Communications, provides the first empirical evidence that fires are hastening the movement of trees, likely by diminishing competition from established species, a news release accompanying the study said.

The authors also explored how to optimize land management amid such ecosystem shifts for forest restoration and wildfire mitigation — areas that are collectively receiving more than $5 billion from the bipartisan infrastructure bill, signed by President Biden into law on Monday.

“Complex, interdependent forces are shaping the future of our forests,” study lead author Avery Hill, a graduate student at Stanford’s University’s School of Humanities & Sciences, said in a press statement.

Past research has already demonstrated that plant ranges are shifting to higher, cooler altitudes at an average of about five feet per year, according to the study. But many of these studies have found that such range shifts lag behind the rate of climate change, with some species ending up stranded in unsuitable habitats — a phenomenon that the Stanford University team aimed to clarify.

The researchers analyzed U.S. Forest Service data from more than 74,000 sites across nine Western U.S. states, identifying tree species that are shifting their ranges toward cooler, wetter sites — a response that the authors said they expected.

But when they compared the rate of range shifts between areas burned by wildfire and those that were not, the scientists found strong evidence that two species — Douglas fir and canyon live oak — experienced larger range shifts in zones that had burned.

While the authors said they have yet to pinpoint precisely how wildfires accelerate this change, they hypothesized that burned areas contain less competition from other plant species, due to the scorched understory and open canopy left in a fire’s stead. When competition does exist, in contrast, the presence of some species may slow the range shifts of other tree types.

These findings, according to the authors, speak to the importance of implementing low-intensity prescribed burns and natural fires, as part of a land management strategy that ensures trees can adapt to climate change.

Such ecosystem processes tend to “have several layers of controls” that can contribute to effective land management, co-author Chris Field, director of the Stanford Woods Institute of the Environment, said in the press statement.

The study, he added, underlines “a natural mechanism that can help forests remain healthy, even in the face of small amounts of climate change.”