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The vast wildfires of this summer and last represent a new normal for the western United States. They may signal a radical landscape transformation, one that will make the 21st century West an ecological frontier.

Unlike fires that have occurred regularly for thousands of years, these fires are so big and so intense as to create discontinuities in natural cycles. In the aftermath, existing forests may not return. New ecosystems will take their place.

“These transitions could be massive. They represent the convergence of several different forces,” said Donald Falk, a fire ecologist at the University of Arizona. “There is a tremendous amount of energy on the landscape that historically would not have been there. These are nuclear amounts of energy.”


Falk’s specialty is fire dynamics in the American Southwest, a region where record fires have become routine. Fueling the infernos is a combination of fire suppression, livestock grazing and logging.

Because small, low-intensity blazes are usually prevented from spreading, dead wood has accumulated, especially in arid and semi-arid regions where decomposition occurs slowly. Without these fires, dense shrubs and small trees proliferate, as they also do in gaps opened by harvesting of large trees. Grazing removes grasses that traditionally carried small fires and causes erosion that reduces soil’s ability to hold water.

Much of the West is now a giant tinderbox, literally ready to combust. Yet thanks to fire suppression, the consequences have been postponed for decades.
“When you look at the long record, you see fire and climate moving together over decades, over centuries, over thousands of years,” said pyrogeographer Jennifer Marlon of Yale University, who earlier this year co-authored a study of long-term fire patterns in the American West.

“Then, when you look at the last century, you see the climate getting warmer and drier, but until the last couple decades the amount of fire was really low. We’ve pushed fire in the opposite direction you’d expect from climate,” Marlon said.

The fire debt is finally coming due. In the Southwest, fires are reaching historically exceptional sizes and temperatures. “The fuel structure is ready to support massive, severe fires that the trees have not evolved to cope with,” said forest ecologist Dan Binkley of Colorado State University. “When the extent of the areas burned becomes large, there are no remaining sources of seeds for the next generation.”

Filling the newly open space will be grasses, shrubs and aspen, said Binkley. The forests will be gone. Something similar may also happen in California’s high-elevation Ponderosa forests, though different plant species will take their place than in the Southwest.

In the greater Yellowstone region, of which Yellowstone National Park is the iconic centerpiece, fire suppression and grazing have less effect on fire dynamics than in the Southwest. Instead, it’s climate that’s changing how fire operates in Yellowstone, said paleoecologist Erica Smithwick of Penn State University.

In 2011, Smithwick was part of a research team that described how Yellowstone fires traditionally occurred on cycles of 100 to 300 years, with its lodgepole pine forests adapted to severe burns every few centuries.

According to the researchers, rising regional temperatures mean fires will become larger and more frequent, with areas burned every few decades. Conifers, which release seeds during fire, aren’t attuned to this pace: The next generation of trees will die before they’re old enough to release new seeds.

“There will be many species that don’t regenerate in that environment,” Smithwick said. “The fire cycle is inconsistent with the species that are currently there.” By 2050, predicted the researchers, much of Yellowstone’s forest could be gone.

It’s hard to say what will come next: grasslands, perhaps, followed by non-conifer forests. Smithwick wouldn’t rule out the possibility that “lodgepole pine could surprise us.” Future successions are difficult to predict.
It’s also difficult to decide whether all these changes, in Yellowstone and elsewhere in the west, are good or bad, desirable or undesirable, something to lament or embrace, or all these things.

The purpose of a national park, for example, is conserving nature — yet preserving Yellowstone as we know it, through fire prevention and engineered post-fire recoveries, may be an act of artifice, with effort required to maintain ecosystems that no longer belong, Smithwick said.

New ecosystems will, of course, be populated by plants and animals “that are just doing what they’ve evolved to do, and their niche space just happens to be becoming more widespread,” Falk said.

“This is on the boundary of ecology and values,” he continued. “As some of these conversions start happening, we can either mourn the loss of naturally occurring ecosystems, which without our mismanagement and climate modification would still be there today, or look at the areas coming back in different forms and say, ‘Okay. That’s the world we created. At least nature has another card to play.’”

“I don’t think it’s clear-cut to say, ‘It’s all destructive,’” said Marlon. “Some species will certainly benefit. But we derive great value from the forests. If we’re to lose forest area, we should look very closely at what we’re losing, and know what we’re losing.”

Interviewed on cell phone while traveling through Arizona, Falk added, “I’m standing up in the San Francisco peaks, outside Flagstaff, looking at a mix of pine and fir. If this went, which it certainly could, and came back as Gambel oak shrubs, I think many of us would see that as a loss.”

If people want to prevent the transformation, it’s still possible to do so through controlled burns and brush removal. “The pressures are very strong, but they’re not inevitable,” Falk said.