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Living with wildfire: Q&A with Winslow Hansen, Forest Ecologist

We should expect that the direct and indirect effects of fire will be an increasingly prevalent part of our lives.

New York City, June 7, 2023 at 2pm. Photo by MTA

winslow hansen
Forest Ecologist

This week, smoke from Canadian wildfires made its way south into the Northeastern US, causing unprecedented declines in air quality. Sunlight was dimmed, haze reduced visibility, and the air quality index fell to unhealthy levels for millions of people.

Fire ecology is a major research area for Cary scientist Winslow Hansen, who directs the newly formed Western Fire and Forest Resilience Collaborative, a multi-year initiative seed-funded by the Gordon and Betty Moore Foundation. Hansen uses field experiments, remote sensing, and simulation models to target forest management that reduces risk of catastrophic wildfires.

Below, he addressed some questions about what we are experiencing, what we can expect in the future, and why we need to advance predictive fire science.

The Northeastern US is not accustomed to dealing with hazardous smoke drift from Canadian wildfires - what's changed? How long will it last?

The smoke we are seeing, and in many cases smelling, is from large fires in boreal forests of Canada. In these ecosystems, while fire is less common compared to drier parts of North America, many of the forests that are burning have experienced fire before, and are home to tree species that are fire adapted. What is changing is the severity of these fires. Climate change driven drought is causing fuels to dry out, increasing flammability and the frequency of fires. Anything that can burn is fuel for a fire – things like shrubs, grasses, and trees. These fires are burning hotter and larger, making them difficult to control. Smoke produced from these fires is carried south by atmospheric circulation patterns. The unhealthy air conditions that have been gripping the Northeastern US are expected to subside by this weekend.

What are the health risks? What can we do to minimize them?

There are real health risks from fires, even if you are only exposed to smoke. The health effects of wildfire smoke exposure range from minor eye and respiratory tract infection to more serious exacerbation of asthma, heart failure, and premature death. The website USAir can give you insight into how fire and smoke are impacting the quality of air where you live. When conditions are unsafe it’s best to stay indoors, if possible, with your windows closed and an air filter running. Drink lots of water and consider wearing a K95 if you need to venture out.

Can we expect more of the same, or is this a one off?

The current fires continue to rage. Warm, dry conditions are expected to make this one of Canada’s most intense fire seasons, which could run through the fall if conditions stay dry. Wind patterns will determine whether we experience smoke again. In the longer term, however, climate change will almost certainly continue to increase burning. The area burned in much of North American forests is increasing at a rapid rate. We should expect that the direct and indirect effects of fire will be an increasingly prevalent part of our lives.

Can you talk a little more about the role of climate change in increasing fire risk?

Climate change is a strong contributor to recent trends in fire. As temperatures warm, the atmosphere is able to hold more water. This causes water to be increasingly pulled from the land’s surface, which dries out trees, downed branches, brush, and other fuels that feed large catastrophic fires. We are seeing longer fire seasons, with heatwaves, drought, and tinder-dry fuels creating the recipe for catastrophic wildfires. Storms with high winds and lightning add to this risk, and can quickly spread fire across the landscape.

What role has human behavior played in the rise in wildfires?

In 1910, a fire known as the Big Burn consumed 3 million acres in Montana, Idaho, Washington, and British Columbia. More than 80 people died - mostly firefighters who were trying to contain the blaze, which was the convergence of hundreds of smaller fires. Entire towns were lost, and the event caught the newly formed US Forest Service on its heels. Many of the first Forest Service employees trained at the Yale School of Forestry, and as East Coasters, they were unaccustomed to fires of the western US.

In the aftermath of the Big Burn, the Federal government steadily embraced fire suppression. This culminated in the 1930s when labor from the Civilian Conservation Corps and a policy called the “10am policy” sought to erase fire from the landscape. The 10am policy decreed that newly ignited wildfires would be extinguished by 10am on the day following their initial report. This policy remained in place for nearly a century, excluding fire from forests that had previously burned for millennia and relied on fire for healthy regeneration.

Fire suppression has led to an accumulation of large amounts of fuel and the densification of live trees in many forested landscapes. This essentially means that trees are growing closer together. When combined with climate change, overly dense fuels can cause high-severity catastrophic fire in forests that previously only had low-severity surface fires.

the big burn
The Big Burn, Idaho, 1910. Source: Library of Congress.

How do wildfires start?

Natural fires are ignited by lightning. However, in the US, people start the vast majority of fires. Between 1992 and 2012, people were responsible for starting 84% of all fires in the US, accounting for 44% of the area burned. Fires can start from embers from campfires, tossed cigarettes, fireworks, burning yard waste, and even sparks from things like power tools.

Catastrophic wildfires are bad for people. They also harm ecosystems. Can you talk a little about that?

In the Western US, we are seeing wildfires that burn so hot that the landscape they leave behind can take decades to recover, if it recovers at all. The scorched land that is left behind makes it difficult, if not impossible, for tree seedlings to survive and establish the next generation of canopy trees. Large swaths of forests are a fire away from becoming shrubland. We are seeing an ecosystem shift happen in a compressed timescale, and it will have implications for biodiversity, carbon storage, and even water availability. Shrublands store less carbon, creating a feedback loop that is pointing us in the wrong direction.

What can we do differently to reduce the risk of future fires?

The most effective way to mitigate the North American fire crisis is radical reduction of greenhouse gas emissions. But at best, this will take decades to unfold. In the meantime, there is real potential for science-based management to reduce the intensity and severity of catastrophic wildfires.

People are increasingly recognizing the benefits of low-severity fire, like prescribed fire, as a management tool in forests that experienced frequent low-severity fire before our policy of suppression. This is incredibly important. Fire is a part of the ecology of forested landscapes through much of North America. Suppression is not a solution. Smaller, low-intensity burns, where ecologically appropriate, could allow us to live with fire in a way that is more sustainable, and reduces the likelihood of future catastrophic fires. In areas where the risk of any fire is too high, ecologically-responsible treatment of fuels can also be effective. This can involve thinning of branches in the lower canopy and selectively removing small diameter trees.

As you can imagine, all of these interventions are incredibly expensive and there are finite funds to address fire risk across the landscape. My lab is focused on combining remote sensing, simulation models, on-the-ground experiments, and stakeholder input to guide management interventions that maximize public safety and forest health.

Do you have a question for Winslow that we can add to this list? Drop an email to:

winslow hansen
Forest Ecologist

Forests influence climate and sustain life globally. Trees sequester carbon emissions that cause climate warming, support much of the planet’s biodiversity, and provide essential services such as fuel, food, and clean water and air. Due to climate change, increasing disturbances, and deforestation, many forests are threatened. Winslow Hansen works to understand where and why forests are at risk, and how we can avoid catastrophic losses.

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