Western forests three times the size of Yellowstone could be transformed by midcentury

Hotter and drier conditions are destroying the ability of many Western conifer forests to spring back after wildfires, a new study has found.

The onslaught of destructive fire and climate change risks turning an area of Western forests three times the size of Yellowstone National Park — about 2.2 million acres — into ecosystems where pine, spruce and fir seedlings cannot grow, according to the study in the Proceedings of the National Academy of Sciences.

But deliberately set, lower-intensity fires offer a way out, researchers noted — and added that this is a method that the U.S. Forest Service had embraced after a long history of fighting all wildfires.

By midcentury, conditions across 7 million acres of Western lands “will be very different,” coauthor Philip Higuera told The Hill.

The front lines of that change are the southern Rockies, the Front Range of Colorado, Northern California and Southern Oregon.

How different these landscapes become depends on wildly different local conditions, the precise character of government interventions — and the broader questions of how quickly the world can slow the burning of fossil fuels, the primary contributing factor to climate change.

But no matter what, “recreation, water quality, and wildlife habitat — all that changes together,” Higuera said. “When we lose these trees from a particular area, all those other components follow.”

The study, which involved more than 50 scientists surveying a representative portion of 27 million acres, found that in many regions, heat, drought and fire are beginning to scour conifers from the landscape.

That’s partly due to higher-severity fires, which consume the fire-resistant seed cones that would usually create the next generation of trees, Higuera said. But it is also due to environmental conditions that are growing ever less hospitable to young, vulnerable saplings — which are far less resilient than mature trees.

Wildfires “accelerates the rate at which forest respond to our changing climate, basically by killing mature trees,” Higuera said. 

That represents an opportunity as well as a threat, Higuera noted. 

Suppose vulnerable trees in rapidly deteriorating eco-regions die in low-intensity fires today, opening up a niche for younger, better-adapted trees to take their place before conditions get too much harsher.

That would mean mature, 20-year-old trees on the land by midcentury — ones better able to weather fire, heat and drought than young seedlings would be.

“If we can maintain — or bring back — fires in these systems that don’t kill all the trees, then we can largely maintain large fire-resistant trees in these low elevation forests,” Higuera said.

That’s an area where the Biden administration is spending big. The administration has already dedicated $3 billion over the next 10 years to reducing fuels across 20 million acres of Western forests — part of a broader plan to reduce fire risk in the West’s sprawling suburbs and exurbs.

If this effort loses steam or fails, “instead of having conifers coming up in the understory after those fires — as typically happened in the past — we have things like grasses and shrubs coming in and dominating,” Higuera said.

But if these interventions are successful, it could yield future forests that are “in many ways broadly similar to what they are right now,” he said.