U.S. forests absorb huge amounts of carbon dioxide, and ambitious efforts are underway to bolster America’s forest carbon sink by planting more trees. However, it is also important to protect the forests we already have. Forest fires, insects and pathogens, and a changing climate all threaten to diminish the carbon sequestration potential of our forests. Scientists generally agree that steps should be taken to protect existing forest stocks and improve forest resilience, but there is a robust discussion around what action to take.
U.S. Nature4Climate convened a panel of experts to discuss strategies to protect existing U.S. forests, with a focus on the carbon impact of forest resilience treatments, like thinning and prescribed fires. Our panel discussed the role that forests play in addressing climate change, and emerging threats to carbon stocks. The discussion then moved to the role that forest resilience treatments, like thinning and prescribed fire, can play in protecting carbon stocks. The panel explored the contexts in which these treatments are most appropriate, discussed factors decision-makers should consider when applying these treatments, and provided guidance on action to support implementation forest and fire management.
- Nathan Henry, Program Manager, U.S. Nature4Climate
- Dr. Matt Hurteau, Professor of Biology – University of New Mexico; forest ecologist
- Maria Janowiak, Acting Director, Northern Institute of Applied Climate Science and USDA Northern Forests Climate Hub – USDA Forest Service
- Dr. Ryan Haugo, Director of Conservation Science – The Nature Conservancy in Oregon
- Dr. Tara Hudiburg, Associate Professor – Department of Forest, Rangeland and Fire Sciences, University of Idaho
What role do forests play in efforts to mitigate climate change in the U.S.?
Our panel kicked off the conversation by emphasizing the important role that forests play in mitigating climate change in the United States. Tara Hudiburg outlined the important role that forests play:
“Forests store massive amounts of carbon and they're keeping it out of the atmosphere and they are helping you stay a little cooler as the planet heats up. We don't want that carbon back in the atmosphere, we want to keep it in the trees and soils.”
Maria Janowiak cited efforts by the USDA Forest Service to quantify the scale of forest carbon sequestration, and the impact it has on U.S. carbon emissions:
“The Forest Service provides data through its tree census, the National Forest Inventory and Analysis Program, about the scale of carbon sequestration. Forests absorb carbon dioxide equivalent to about 10% of the U.S. emissions from fossil fuels. People are increasingly recognizing the value of forest lands can play in sequestering carbon, which contributes to mitigation targets for addressing climate change.
However, panelists stressed that forest carbon sequestration is not a substitute for efforts to decarbonize the U.S. energy and transportation sectors. Ryan Haugo noted that “Forests are hugely important in the U.S., but they are secondary to reducing our fossil emissions and it’s a complementary effort. First and foremost, is reducing fossil emissions.”
Matt Hurteau also emphasized that forests should not be seen as a substitute for broader de-carbonization efforts:
“There's no way that we're going to increase forest carbon sequestration or any natural system sequestration to the point that we don’t need to stop burning fossil fuels. Functionally, any sort of uncertainty around forest carbon accounting pales in comparison to the gains that we can make by stopping the burning of fossil fuels.”
Emerging threats to U.S. forest carbon stocks
U.S. forests stocks face multiple threats, from human conversion of forests to other land uses to increased wildfire risk to increased mortality from insects and pathogens. Many of these threats are being intensified by the impacts of climate change. Matt Hurteau summarized these threats:
“The three main threats to carbon stocks include human land use, climate change, and climate-driven increases in disturbance size and severity. Disturbances include insect outbreaks and fire and climate change is turning up the intensity of their impact. In the U.S., with climate change and climate-driven increases in disturbance, we’re absolutely on a trajectory of worsening conditions for forests.”
Tara Hudiburg highlighted the specific threats posed by increased heat and fire risk:
“We’re seeing increases in drought and aridity and the increases in disturbance, and now we’re getting these heat domes in the Pacific Northwest like we saw last summer, which are extremely damaging for anything that photosynthesizes, leading to foliage damage.
I also read recently that in the next 10 years, we can expect a 50% increase in the number of days that are suitable for fire. That’s a 50% increase in the number of days that things can burn.”
Maria Janowiak noted that climate impacts cause feedback mechanisms that multiply threat to our forests:
“These interactions build and build and build. They have already been happening for a long time, and they are multiplying, so the intensity, the frequency, and the pace of all of the impacts are becoming more rapid, to the point that it feels out of control in a lot of landscapes.”
What should we be doing to protect forest carbon stocks?
Our panel largely believed that forest protection efforts should have broader goals than just storing more carbon. Matt Hurteau suggested that forest protection should focus on maintaining ecological systems:
“Our best approach to climate mitigation in forests is to think about how we maintain a well-functioning ecological system. What do we need to do to get there? Do we need to do anything? In some places, we may need to do nothing, and in other places we may need to take action because we’ve knocked the system so far out of whack.
Maria Janowiak stressed the importance of taking a long view when developing strategies for protecting forests — focusing not just on the current situation, but also anticipating future conditions:
“I think one of the pieces that gets lost in the near-term focus on meeting carbon targets is the long-term vulnerability of an ecosystem from climate change. Just focusing on current conditions without the broader context of how climate change and other stressors could play out in forests can lead to short sighted actions.”
For more information about one innovative program working to increase forest resilience, see U.S. Nature4Climate’s video “Building Capacity for Reforestation in a Changing Climate”
Ryan Haugo cited the important role that privately-owned forest lands can play in efforts to protect forests:
“There are exciting conversations happening right now in Oregon about strengthening the state’s Forest Practices Act on private forests including increasing forest buffers around streams and rivers. There has also been interesting research on the carbon benefits of managing private lands following Forest Stewardship Council certification standards.
Neither are specifically designed to produce carbon benefits, but both will have positive outcomes on forest carbon stores. Actions like expanding riparian protections on private land, and following sustainable FSC certifications can promote values like biodiversity, water quality, and can also help protect our forest carbon stocks.”
What are forest resilience treatments, and what are their impacts?
The panel then turned specifically to the role that forest resilience treatments can play in protecting forests, and the impact that these treatments have on carbon stocks, focusing on strategies like thinning and prescribed fire. Matt Hurteau explained why land managers undertake these strategies:
“From a forest restoration perspective, thinning is about restoring a process – in this case, fire – to an ecosystem. The types of forest where this action is most appropriate are in ecosystems that, prior to our efforts to put fires out, burned on average every 40 years or fewer.
In these historically “frequent-fire forests,” thinning is about raising the height to the forest canopy. This means retaining the big trees, removing some of the small trees, which we call ladder fuels to prevent or reduce the chance that fire will climb from the forest floor up into the canopy. Once these treatments are done, fire can be reintroduced to reduce the dead biomass – or fuel – on the forest floor."
Ryan Haugo emphasized that thinning should be done in service of a specific goal – to reintroduce fire into forest ecosystems:
“In thinking about our dry, historically frequent fire forests in the West, fire is the ecological process that needs to be returned to the ecosystem, and thinning is a step that may be needed to put fire back into the ecosystem.”
Maria Janowiak added that the context in which these strategies are undertaken influences how these tools are used:
“It's important to recognize that thinning and prescribed fire are tools in a toolbox used by land managers to achieve broader management goals for the ecosystem. Those goals vary widely across different ownerships, and how these tools get implemented is influenced by the management context of the site, its land use history, and the goals of the entities involved. That is where it becomes difficult to determine how we should manage for carbon with any specificity, because it is so context-dependent on those other factors.”
Tara Hudiburg cautioned that when thinning is done on public forests, it has not always followed scientific principles, and where it hasn’t, it can actually worsen conditions:
“In many cases where thinning has been enacted in the Pacific Northwest, there has been a difference between what scientists have said should be done, and what has actually happened. The thinning has been done more for commercial reasons. In other words, large-diameter trees - not ladder fuels - were removed. So, if you were trying to thin to protect carbon, you lost big time. You probably didn’t improve the ecosystem either, because you took in machinery impacting soils, and you may have made it hotter because you’ve removed some of the cooling effects forest have through evapotranspiration. It is essential that we protect large-diameter trees in whatever treatment is proposed."
Uncertainty about future fire risk
One of the challenges discussed by the panel was the fact that strategies like thinning and prescribed fire yield uncertain long-term benefits. As Maria Janowiak explained:
“There's a lot of uncertainty regarding the climate and other disturbance impacts. We know these things are happening and will continue to happen with increasing frequency and severity in many contexts, but the exact details regarding when and where they happen is unknowable.
Tara Hudiburg reinforced this point, while adding that the sheer size of American landscape poses management challenges:
“You can't predict where the fire is going to be. You know that it's probably going to happen somewhere, and that it has a higher probability in some places, but trying to manage millions and millions of acres for when and where is unrealistic. .”
Matt Hurteau noted that the likelihood that fire will occur in a given landscape is a key part of the decision-making process on whether or not to undertake resilience treatments:
“We have imperfect information about what the future holds, but we're not flying blind. We have to think about the chance that a disturbance happens in a given place – and that’s going to vary depending on where you are.
If you're on the Olympic Peninsula in Washington, the chance that a wildfire starts is about the same as the odds of winning the Powerball Lottery – there’s a very low chance that a wildfire will start in a given year. Whereas, in Arizona or New Mexico when the dry lightning starts in monsoon season every year, where there are plenty of ignition sources and it's always dry enough to burn during fire season, the chances of a fire starting are higher – more like the chance of getting a speeding ticket if you are pulled over in a school zone. It's still not 100% going to happen every year, but it is a heck of a lot higher than in other locations.
Our understanding of the chance of a disturbance occurring factors into the math of figuring out how big the carbon consequence is likely to be, and how long it will persist.
Ryan Haugo noted that forests that fall between these two examples pose special challenges in developing strategies to manage wildfire:
“There’s a middle zone – what we sometimes call mixed-severity forests – where our understanding of the future direction of the fire regimes is more uncertain. For example, in the Northwest, we experienced the Labor Day 2020 fires in the Western Cascades. Very large fires have previously been recorded in these forests, but when it happens it’s still shocking.
I don't think we've coalesced around an understanding of what it means to live in or to manage forests in that context. How is climate change going to change the likelihood of fires in forests that historically experienced more infrequent and mixed or high severity fires ? There are some areas where our uncertainty is greater in terms of understanding where fire is going in the future.”
Fire is a part of life in the West
Our panelists noted that, no matter what actions we take to mitigate fire risk, forest fires are going to be a fact of life in parts of the country for the foreseeable future. As Ryan Haugo noted:
“There's no future without fire and smoke. We have to learn how to adapt to that in our landscapes and communities, and think about how we target investments in our forested landscapes. It's not just funding for prescribed fire, it's not just funding for thinning, and it’s not just funding for developing smoke-ready communities – you have to do all of it together, and it needs to be coordinated and integrated.”
Tara Hudiburg suggested that the most effective long-term solution to reducing the impacts of wildfires is reducing fossil fuel emissions:
“Cities like Portland are not going to stop experiencing smoke, nor are you going to be able to stop the increasing occurrence of wildfire until we eliminate fossil fuel emissions and correct the climate. We're not going to mitigate our way out of climate change with land treatments alone. You’re still going to get smoke in Portland.”
Matt Hurteau added that reducing the intensity of smoke and developing an effective societal response to fire is key:
“Even if we weren't experiencing human-caused climate change, we should fully expect to be breathing some level of smoke during the fire season. The ideal situation is that we expand our capacity to reintroduce ecologically-appropriate fire in forests, that will change the dose of smoke we get in any given event. However, we also need to see a societal response, in the form of updated building codes and other measures, that can help lessen the impact of fires on communities when they do occur.”
Utilizing new resources for forest management
The recently passed Infrastructure Investment and Jobs Act passed with bipartisan support , includes billions of dollars for a wide range of activities, from reforestation to increased fire management. Ryan Haugo suggested a need to consider a wide range of goals when making decision on how to implement programs on the ground:
“We need to use the funding to promote and manage our forests for resilience, and for the wide range of benefits that we rely on from our forests across the U.S. It's not just carbon, it's not just wildlife, it's not just water – it’s all of those things together.
Matt Hurteau advocated for developing a workforce to reduce stress on existing fire crews, and improve our capacity for both managing wildfires and undertaking forest resilience treatments:
“We have let the human capital in natural resource management decline for the last 40 years, so we don't have enough people working in “green jobs”. When I look at the stress our wildfire suppression crews are under, the challenges they are facing, and the personal consequences that many are experiencing, we can't possibly expect somebody to roll out of a Dixie Fire, after working 12-16 day shifts in the heat of the California fire season, and then assume that they will be physically and mentally capable of going out in the fall and lighting prescribed burns in New Mexico.
We need to think about dedicating a billion dollars a year, and using it to develop fire professionals whose job it is to work with fire in an ecologically beneficial way on the landscape. That includes putting people out there to manage a natural ignition that occurs in the Gila Wilderness or the Yosemite backcountry in an ecologically beneficial manner. It also includes planning and implementing prescribed fires where we need them to occur.”