A mile south of Yosemite National Park, fire ecologist Chad Hanson strides through the Stanislaus National Forest, heading to a great gray owl nest he found earlier this spring. Genetically distinct from its cousins in western North America, these rare birds are two feet tall, with a wingspan of about five feet. They can be seen almost any time because, unlike most owls, they are active day and night.
There are, however, only 200 to 300 adults remaining in California’s forests, which have been battered by drought, insects, rising temperatures, and fire. In the nearly five years that Hanson — principal ecologist with the John Muir Project, a non-profit group devoted to the ecological stewardship of federal forests — has been conducting research in the Sierra Nevada, he has yet to see an adult gray owl. They are almost as rare as the spotted owls that dwell in the region.
As Hanson and I move into the site of the 2013 Rim Fire, which burned a record square 400 miles in the region, we spot a great gray owl in a snag — a bare, fire-scarred tree. Hanson is elated, not so much for the opportunity to finally see an adult of this species in the Stanislaus, but because it drives home a point he has been making about this fire: Despite the widespread devastation, the forest ecosystem is rebounding on its own, without help from federal foresters, who soon after the fire initiated a program of logging and replanting in other areas. On our hike, we pass acre after acre of young tree species and shrubs greening the once-charred landscape of this so-called snag forest.
“Since the Rim Fire burned, we’ve had this steady stream of people insisting that this was one of the most catastrophic and devastating fires in California history,” says Hanson. “They claimed that nothing would grow back, that the owl and deer populations could not be sustained. They, and others, are using it as an excuse to accelerate the clear-cutting of snag forests.”
The Rim Fire has become the latest front in a long-running debate over how best to help forests regenerate after major fires, which are becoming more frequent in places like the western United States as climate change boosts temperatures and causes worsening droughts. Some scientists contend that in an era of more widespread and intense wildfires, forests now need human help to bounce back, especially when blazes sweep through the same area within a decade or two. The Rim Fire, according to U.S. Forest Service ecologist Jay Miller, “nuked” much of the landscape, necessitating a program of logging and replanting.
Federal and state agencies, along with timber harvesting interests, are making the case that clearcutting and replanting is the best way of ensuring regeneration. This will, they say, reduce the risk of future fires, remove the threat of burned trees falling on forest workers or visitors, and mitigate the impact that a big fire has on the environment and the regional economy. In 2016, the Forest Service sold $186 million of Rim Fire timber.
Leaving high-severity burns to regenerate on their own, the Forest Service says, increases the amount of fuel on the ground that could make future fires more intense. And some Forest Service studies suggest that logging causes neither a reduction in total plant cover nor an increase in the abundance of exotic species. A key factor today, according to some foresters, is that policies calling for the extinction of all fires — often instituted to protect nearby homes, infrastructure, and businesses — have upset the natural order of things. As a result, human intervention may sometimes be necessary to revive forests, logging proponents say.
A bill is now making its way through the U.S. Senate that would speed up this kind of clearcutting and weaken environmental laws that protect national forests — including burned areas — and the threatened species that dwell in them.
The Forest Service has some allies in the conservation community. Several months after the Rim Fire was extinguished, Eric Holst, a vice president of the Environmental Defense Fund, penned a blog stating that “letting nature heal itself” after a high-intensity fire is likely to result in a forest dominated by shrubs for many decades.
The Forest Service did not do all the logging it wanted at the Rim Fire site because the Center for Biological Diversity and the John Muir Project, an organization that Hanson co-founded, went to court in 2014 to stop the clear-cutting. They lost the case. But the delay was long enough to dissuade the Forest Service from doing additional cutting, presumably because the value of the timber decreases with decay.
Hanson and 249 likeminded scientists argued in a 2013 letter to Congress that conflagrations such as the Rim Fire — and the snag forest it produced — have been beneficial to the ecosystem. Great gray owls are nesting on the edge of this high-intensity burn, hunting for rodents attracted to the open meadows and burned-out areas like the ones we hiked through. Black-backed woodpeckers, a bird that is being considered for listing under the Endangered Species Act, are thriving on fire beetles that lay their eggs on snags. These larvae get fat feeding on the decaying wood. Cavity nesters such as mountain bluebirds, western screech owls, flying squirrels, and fishers exploit the cavities drilled by woodpeckers. As many spotted owls live in the Stanislaus forest now as before the fire, according to the non-profit research organization Wild Nature Institute.
The deeper Hanson and I hike into a badly burned area that has yet to be clear-cut, the more verdant and biologically diverse the vegetation becomes. We see Douglas fir, Ponderosa pine, sugar pine, and black oak rising up from a forest floor carpeted with whiteleaf manzanita and mountain misery, a highly aromatic shrub that oozes sticky black gum. A red-tailed hawk swoops by in an open meadow.
Hanson points to one cluster of 5-foot-tall pines, veritable giants compared to the seedlings that the Forest Service planted in its clearcuts after spraying herbicides to reduce competition for water, nutrients, and sunlight. Most of the Forest Service conifer seedlings that we saw when we visited a plantation earlier in the day were either dead or dying. None were more than two feet tall.
“Basically, clear-cutting and spraying herbicides amounts to kicking a forest when it’s down and trying to regenerate on its own,” Hanson says. “The heavy machinery used to cut down the snags destroys the conifers that are trying to grow naturally. The herbicides prevent the growth of native shrubs and forbs that are beneficial to animals. They favor instead invasive species.”
Hanson stops to show me a snag that is pock-marked with hundreds of holes that had been pecked out by black-backed woodpeckers. “One black-backed woodpecker needs to eat 13,500 wood-boring beetles in order to survive,” he says. “A pair of woodpeckers supporting chicks needs 200 to 300 acres of snag forest. Without these snags we would not have the diversity of insects we have, nor the woodpeckers and other wildlife that depend on them … Snag forests are as ecologically important as old growth forests and other forest ecosystems. But there is no protection for them.”
The scientific literature on post-salvage logging is contradictory. Some studies argue that the practice is beneficial because it churns up the ground, softening hard, water-repellent soils that sometimes form after an intense fire. Proponents also insist that the detritus left behind after logging inhibits erosion.
Critics such as Hanson say that the logging skidders decrease natural forest regeneration, kill seedlings, and compact the soil in a way that increases runoff and erosion, harming aquatic life in streams and rivers.
In some cases, intense fires have severely modified a forest landscape. That has happened in the boreal forest of Canada and northern Minnesota. Major fires burned twice, for example, in Wood Buffalo National Park — once in 2004 and again in 2014. Those blazes, along with another 384 fires in the Northwest Territories, burned a record 8.5 million acres in 2014.
Since the second fire, there is little evidence of aspen and pine popping up as they did after the first fire. If strong winds blow in pine seeds from far-off unburned areas, they probably will not germinate because the fires’ heat vaporized most of the organic matter in the soil.
“That was a pine forest for centuries,” says Marc-Andre Parisien, a research scientist with the Canadian Forest Service. “It may be decades or even centuries before it’s a pine forest again.”
Ellen Whitman, a Ph.D. candidate at the University of Alberta, has worked in Wood Buffalo. She says the outlook in the park initially seemed bleaker than it’s turning out to be because of a period of intense drought that followed the second fire. She doubts, though, that the pines will return anytime soon because the second fire destroyed the young, 10-year-old pines that act as a seed crop. In addition, she says, the 2014 fire was “so severe that it completely removed what was left of the organic soil layer. Seeds are trying to grow on sand that doesn’t hold much moisture. Some vegetation is coming back, but there is almost no sign of trees.”
The Bob Marshall Wilderness in Montana (locally known as The Bob) is one of the very few places in the U.S. where fires have been allowed to burn and where post-fire logging has been off limits for the past century. University of Montana forest ecologist Andrew Larson says the forest there regenerates very well after moderate- to high-severity fires. The exception, he says, is in areas that have reburned in less than 20 years, too soon to allow for a seed crop to mature, especially on the west- and south-facing slopes that are hotter and drier.
“On these sites, we see dominance by different shrubs and grasses with just a few widely distributed conifer seedlings,” says Larson. “These sites may be unforested open areas for many decades. Most reburn areas in the Bob are coming slowly back to forest, but some fraction of the most severely burned areas on hot, dry slopes will be non-forest or pre-forest for probably most of the next century. This is not necessarily a bad thing, but it is certainly a different landscape from what many people remember from before the recent period of active fire, which started around 2000.”