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Scientists Say Clearing Forests Worsens Wildfire Damage

Wildfires aren’t caused by forests, but the default approach to fire prevention is to clear them. Climate may be the real problem, and preserving trees a big part of the solution.

New research suggests that thinned forests burn more intensely, as in this area affected by the 2020 Creek Fire, near Shaver Lake, Calif. (Chad Hanson)
The number of acres burned during the 2020 wildfire season exceeded 10-year averages for both California and the U.S. as a whole, and the 2021 season is expected to have a larger footprint. According to the National Fire News from the National Interagency Fire Center (NIFC), almost 6,200 more wildfires occurred by mid-July 2021 than were seen by the same time in 2020.

At present, nearly 70 wildfires are in progress in 12 states. With big fires ongoing simultaneously in multiple locations in hot, dry states, the National Multi-Agency Coordinating Group (NMAC) has elevated the National Preparedness Level to 5, its highest level, the earliest it has done this in the past 10 years. At PL5, says NMAC, “at least 80 percent of the country’s IMTs [incident management teams] and wildland firefighting personnel are committed to wildland fire incidents.”

Wildfires have an important role in ecosystem processes, but the hotter, drier weather resulting from climate change creates conditions that make them more likely. Human incursion into forested areas, and their behavior once there, also creates fire risks. Humans are responsible for starting 84 percent of all U.S. wildfires, and 97 percent of those that threaten homes. Researchers from UC Irvine found that fires caused by humans spread twice as fast in California forests as those caused by lightning.

From this perspective, people might seem the most obvious target for fire prevention efforts. In addition to causing accidental (and sometimes intentional) ignitions, human activity is accelerating warming. However, the prevention strategies advocated by government entities tend to focus on removing trees and “snags” – dead trees that are still standing but continue to play an important role in ecosystems.

Chad Hanson, Ph.D., an ecologist who co-founded the John Muir Project, is a prominent member of a growing community of scientists who challenge the notion that practices such as thinning and clear-cutting back-country woodlands will reduce the severity of wildfires. In a new book, Smokescreen: Debunking Wildfire Myths to Save Our Forests and Our Climate, he describes how recent research regarding fire behavior and ecology could provide the foundation for a new approach to forest management.

Most recently, Hanson used Forest Service data as the basis for a study of two large fires that occurred in California in 2020: the Creek fire and the Castle fire. The research, which will be published later this year, found that intensive forest management was most correlated to burn severity, not the density of snags or the length of time since the last fire in an area.

Hanson sees a dangerous political narrative developing, at state and national levels and among members of both political parties, based on an assumed association between forest density and risk. This notion has been refuted in numerous studies, including one that looked at 1,500 fires between 1998 and 2014.

“That narrative is being used and weaponized to target logging projects at old growth forests and some of our most ecologically sensitive and vulnerable forests, based on the idea that those are the most so-called overgrown,” he says. “Not only will this damage wildlife habitat and make climate change worse, when fires burn those areas again, they will burn more intensely.”
Same fire, different outcomes. The 2020 Creek fire in California burned almost 400,000 acres. The photo on the left shows fire effects in a section that had been thinned before the fire. The photo on the right shows fire effects in a section that had not been cleared. (Chad Hanson)
In a conversation with Governing, Hanson discussed some of the concepts covered in Smokescreen.

Governing: What’s the most damaging misconception about forest fires?

Chad Hanson: The most important point to confront is what I call the overgrown forest myth. Scientific data is confirming that denser forests, older forests, forests with more biomass in them, forests that haven't burned in a very long time, are not burning more intensely.

If these forests have no logging history, it doesn't matter how dense they are. It doesn't matter how long it's been since they burned. It doesn't matter how many dead trees or downed logs they have, or how many trees per acre. Those forests do not burn more intensely than forests in the same forest type that have been logged, in the same fire.

Governing: Why wouldn’t a dense forest burn more intensely?

Chad Hanson: Logging changes the microclimate of a forest and creates a microclimate that is more conducive to the spread of flames and more intense fires, when a wildfire occurs. A dense forest that has a lot of trees and a lot of biomass also has a high canopy cover and it has a lot of cooling shade from that canopy cover. The trees, alive and dead, and the downed logs soak up and retain huge amounts of moisture and soil moisture.

You have a lot more water in the system overall, even in the ambient air. The ambient air temperature is lower and the relative humidity is higher. The higher level of tree density acts as a windbreak against the winds that drive flames. Everything stays more cool, more moist, more shaded.

When logging occurs, you reverse that. The canopy cover is reduced and this creates hotter, drier and windier conditions. In addition, logging equipment spreads highly combustible, invasive grasses and leaves behind kindling like slash debris, which is also highly combustible.

Governing: If there’s science showing that logging makes fires worse, why isn’t that science the basis of policy?

Chad Hanson: Fires are highly variable. There are always a few areas where some kind of thinning operation was conducted and the fire burns at low intensity. When scientists look at the entire fire, as I’ve done with last year’s Creek fire and Castle fire, we're finding that logged areas are burning more intensely.

The problem is that the U.S. Forest Service and others are taking people to those few locations that are the exceptions and implying to them that they are the rule, and that thinning is effective.

Fire ecologist Chad Hanson describes the protective microclimate in undisturbed forest.

Governing: Some states with the worst fire problems seem to have progressive leaders who embrace science. Is the work that you and your colleagues are doing getting through to them?

Chad Hanson: California has one of the most environmentally hostile and climate-unfriendly administrations that we've ever seen, particularly when it comes to forests. There’s a serious threat from leaders who say they take climate change seriously, who make speeches about how science matters and evidence matters, but behind the scenes, are promoting policies that would double down on logging, including logging of big trees and even clear cuts, and approving oil and gas leases.

There are Democrats in Congress who do care about the science and want to do the right thing, but there are also Democrats in positions of power who are taking contributions from the logging industry. Their policies reflect that – they are promoting logging every chance they get.

Governing: What’s your take on the most recent proposals to address fire risks?

Chad Hanson: The Democrats’ infrastructure bill has billions of dollars of new logging subsidies. We can’t afford to do that.

We have to move away from back-country logging and protect our forests for climate change mitigation, for biodiversity conservation and to protect communities, and redirect resources and subsidies into jobs that create fire-safe homes and fire-safe towns.

Governing: Climate is increasing wildfires. Is there a way out?

Chad Hanson: In order to overcome the climate crisis, we have to do two things: We have to get away from fossil fuels as quickly as possible, and we have to dramatically increase the protection of natural ecosystems that store and absorb carbon.

Your biggest bang for your buck is forests in terms of carbon absorption, and most of the forests in this country and around the world have far less carbon in them than their biological potential because of decades of logging.

Here’s why this matters so much. We've had a global pandemic since early last year that’s had the effect of significantly reducing fossil fuel consumption and carbon emissions nationally and globally. Yet during that same period of time, the concentration of greenhouse gases in our atmosphere have gone up from 414 parts per million of CO2 equivalent to 417 parts per million.

Why is that? Once we put excess CO2 in the atmosphere, it has very, very long residence time – it stays up there for many, many decades, even centuries. We have to get away from fossil fuel consumption, but that's not enough.

We will not avoid the worst impacts of the climate crisis unless we do the second thing, which is draw down atmospheric carbon through nature-based climate solutions, primarily protecting forests and shifting away from logging and wood consumption.
Chad Hanson: "In order to overcome the climate crisis, we have to do two things: we have to get away from fossil fuels as quickly as possible and we have to dramatically increase the protection of natural ecosystems that store and absorb carbon." (Chad Hanson)

Governing: Recent extreme heat events in the Pacific Northwest shocked climate scientists, causing worries about effects we haven’t considered. What might we be missing or underestimating about climate and forests?

Chad Hanson: Our levels are dangerously high already at 417 parts per million. We need to bring them down to well below 350 parts per million to avoid the worst impacts of the climate crisis. This is the critical time period.

We need to keep carbon in the ground and in our forests. We need to consume less, build smaller houses, use more recycled materials and more nonwood materials for paper and for housing construction. There are all kinds of alternatives to wood now, things that are much better for biodiversity and much better for the climate.

If we ignore these things, CO2 concentrations will keep climbing into even more dangerous territory, and more unexpected and dangerous things will happen, only so many of which we'll be able to predict.

The good news is that if we turn the corner over the course of the next 10, 15, 20 years, atmospheric CO2 concentrations will not only stop going up, but eventually they'll start coming down. Global temperatures will start cooling, and we'll start seeing a reversal of these dangerous patterns, extreme climate events and anomalies that we're seeing now.

Governing: These things will take time to implement. What can be done to help us through the current fire season?

Chad Hanson: The vast majority of wildfires near communities are caused by humans. We need more people, more patrols and various levels of government working to prevent accidental human ignitions and arson near communities, especially in the lower-elevation environments where you have some of the hottest and driest conditions.


Carl Smith is a senior staff writer for Governing and covers a broad range of issues affecting states and localities. He can be reached at or on Twitter at @governingwriter.
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