When boreal forests burn in the Far North of the U.S. and Canada, the whole world feels the impact. From communities evacuating from the blazes, to smoke clogging the air thousands of miles to the south, to the release of carbon emissions that accelerate climate change, boreal forest fires are a global issue.
Research from Woodwell Climate has recently expanded our understanding of the scope of impact that boreal fires have. A new paper, led by Research Associate Stefano Potter, quantified emissions associated with fires across most of boreal North America, shedding light on the dynamics of boreal fires and climate change. These four graphics explain:
Using a new higher-resolution dataset, generated as part of NASA’s Arctic-Boreal Vulnerability Experiment (ABoVE), Potter and his co-authors created a map of burned area across the boreal region. The researchers combined satellite imagery with observations from the largest database of boreal field studies, which allowed them to calculate emissions from both vegetation burned aboveground, and organic matter in the soils that burned belowground.
The results show that the overwhelming majority of carbon emissions from boreal fires—over 80% of total emissions in most places—comes from soils rather than trees. Despite the dramatic imagery of burning forests, most of the real damage is happening below the ground.
That finding on its own was not surprising to researchers, as the majority of carbon in boreal forests is stored below the ground. However, the fact that the overwhelming contribution of belowground carbon to fire emissions is being left out of existing global fire and climate models, means we’re drastically underestimating carbon emissions from Arctic and Boreal environments.
“A large reason for that is because the [existing] models are not detecting the belowground carbon combustion, which we are modeling directly,” says Potter.
Potter and the team working on the paper were able to accurately model belowground carbon loss because of their machine learning approach and the abundance of available field measurements in their dataset.
Accurately representing these numbers in global fire models is critical, because these models are used to plot climate trajectories and inform carbon budgets, which tell us how much we need to cut emissions to stay below temperature thresholds like 1.5 or 2 degrees C.
It is becoming more urgent to get an accurate understanding of boreal emissions, because boreal fires are becoming larger, more frequent and more intense. Burned area has increased as fire seasons stretch longer, return intervals between fires shorten, and single ignitions can result in massive blazes that burn further and deeper and cause greater carbon loss.
In 2023, for example, while the number of ignitions has been lower than most years since the 1990s, burned area as of August has far surpassed any year in the past three decades.
Ultimately, preventing carbon loss from boreal forest fires will require bringing down emissions from other sources and curbing warming to get fires back within historical levels. But preventing boreal forests from burning in the short term can offer a climate solution that could buy time to reduce other emissions.
A collaborative study between Woodwell Climate and the Union of Concerned Scientists, published in Science Advances, modeled the cost effectiveness of deploying fire suppression in boreal North America and found that actively combatting boreal fires could cost as little as 13 dollars per ton of CO2 emissions avoided—a cost on par with other carbon mitigation solutions like onshore wind or utility-scale solar. Informed by this data, the U.S. Fish and Wildlife Service has decided to start combating fires in Yukon Flats National Wildlife Refuge, not only when they present a threat to human health, but also with the intent of preventing significant carbon losses. Yukon Flats is underlain by large swaths of carbon-rich permafrost soils, at risk of thawing and combusting in deep-burning fires.
Deepening our understanding of the complex boreal system with further research will help inform additional strategies for bringing emissions under control, preventing devastating fires that threaten human health both regionally, and across the globe.
Canada’s fire season has barely started and it’s already on track to break records. So far, NOAA has documented more than 2,000 wildfires that have resulted in the forced evacuation of over 100,000 people across Canada. The most recent bout of fires burning in Ontario and Quebec has sent smoke southward into the Eastern U.S., causing record levels of air pollution in New York and warnings against outside activity as far south as Virginia.
Only a little over a month into the wildfire season, fires have already burned 13 times more land area than the 110-year average for this time of year, and they show no sign of stopping, according to Canadian publication The Star. Indigenous communities, some of whom live year-round in remote bush cabins, have been particularly harmed by the blazes.
According to Woodwell Climate Senior Scientist Dr. Jennifer Francis, the phenomenon of winds pushing smoke down to the northeastern U.S. has been linked to rapid Arctic warming caused by climate change.
In the upper atmosphere, a fast wind current called the jet stream flows from west to east in undulating waves, caused by the interaction of air masses with different temperatures and pressures, particularly between the Arctic and temperate latitudes.
As global temperatures have risen, the Arctic has warmed two to four times faster than the average global rate. Dr. Francis stated in an interview in the Boston Globe that the lessening of the temperature differences between the middle latitudes and the Arctic has slowed down the jet stream, which results in a more frequent occurrence of a wavy path.
Another factor contributing to the widespread smoke is an ongoing oceanic heat wave in the North Pacific Ocean. The blob of much-above-normal sea water tends to create a northward bulge in the jet stream, which creates a pattern that sends cooler air down to California and warm air northward into central Canada—resulting in the persistent heat wave there in recent weeks. Farther east, the jet stream then bends southward and brings the wildfire smoke down to the Northeast.
“Big waves in the jet stream tend to hang around a long time, and so the weather that they create is going to be very persistent,” Dr. Francis said. “If you are in the part of the wave in the jet stream that creates heat and drought, then you can expect it to last a long time and raise the risk of wildfire.”
The wildfires are also decimating North American and Canadian boreal forests, the latter of which holds 12 percent of the “world’s land-based carbon reserves,” according to the Audubon Society<./a> And three quarters of Canada’s woodlands and forests are in the boreal zone according to the Canadian government.
“The surface vegetation and the soil can dry out pretty dramatically given the right weather conditions. For this fuel, as we call it in fire science, it often just takes one single ignition source to generate a large wildfire,” said Woodwell Climate Associate Scientist Dr. Brendan Rogers.
As the climate continues to warm, Dr. Rogers said the weather conditions that lead to fuel drying and out-of-control wildfires also increase. This creates a feedback loop. Heat waves caused by greenhouse gas emissions increase the prevalence of wildfires. The fires in turn destroy these natural carbon sinks and, in turn, speed up climate change.
While the ultimate solution to breaking this feedback loop lies in reducing emissions and curbing climate change, Dr. Rogers and other researchers at Woodwell Climate have conducted research into fire suppression strategies that could help prevent large boreal fires from spreading and help keep carbon in the ground.
A study conducted in collaboration with Woodwell and other institutions found that suppressing fires early may be a cost-effective way to carbon mitigation. Woodwell Climate’s efforts also include mapping fires, using geospatial data and models to estimate carbon emissions across large scales, and looking at the interplay between fires and logging.
“Reducing boreal forest fires to near-historic levels and keeping carbon in the ground will require substantial investments. Nevertheless, these funds pale in comparison to the costs countries will face to cope with the growing health consequences exacerbated by worsening air quality and more frequent and intense climate impacts expected if emissions continue to rise unabated. Increased resources, flexibility, and carbon-focused fire management can also ensure wildlife, tourism, jobs, and many other facets of our society can persevere in a warming world,” Dr. Rogers said.
Transcript edited for grammar and clarity.
Sarah Ruiz: Fire. It’s a transformative force on any landscape, scorching and destroying, but often making space for new life. It also plays a part in transforming our global climate, releasing stored carbon from forests and other ecosystems that we simply cannot afford to add to our atmosphere. I’m here today with three of Woodwell Climate Research Center’s experts on fire and climate change: Dr. Manoela Machado, Dr. Brendan Rogers, and Dr. Zach Zobel. We’re here to discuss how fire fits into the climate change puzzle, as both a symptom and the cause of the warming climate. Consider this a “fireside chat” of sorts. Let’s begin.
Brendan, you work primarily in boreal forests, where fires are a natural part of the landscape, correct?
Dr. Brendan Rogers: Yes, that’s right. So even though boreal forests are in the north and they’re cold and damp for a lot of the year, the surface vegetation in the soil, the soil organic matter can dry out pretty dramatically in the summer. This fuel, as we call it in fire science, often all it takes is just one single ignition source to generate a pretty large wildfire. Humans certainly ignite fires, but still most of the burned area in boreal forests is coming from lightning ignitions.
Fire is also an important natural process in boreal forests. Many of the fires are what we call stand replacing—meaning they’re high intensity, they kill most of the trees, at least in Alaska and Canada. This initiates the process of forest succession, with often different types of vegetation, and tree species playing pretty key ecological roles. But fire regimes are changing and intensifying with climate change, taking us outside the range of what we would consider our natural variability that we’ve seen in these systems for millennia.
SR: Now, Manu, you work in the Amazon rainforest, where fire is never a natural part of the landscape. Can you explain what Kind of role fire plays in a tropical rainforest?
Dr. Manoela Machado: The Amazon biome did not evolve with fire pressure selecting for strategies of survival, which means that the plants are not adapted to this disturbance. Fire is a very powerful tool used to transform the landscape and has been used for millennia. Traditional and Indigenous communities still use it for agricultural purposes, but that’s not the fire that we see on the news, making headlines of “fire crisis in the Amazon.”
Those catastrophic events with lots of smoke in the atmosphere, they’re normally related to deforestation fires, which are fires used after clear cutting to clear out biomass and use the land for cattle ranching and other agricultural purposes. Those fires can escape into forest areas. So the ignition sources are always human—there are no natural ignition sources in the Amazon forest.
SR: With climate change, these dynamics are shifting in many places, as drier and hotter conditions make it easier for fires to spark. Zach, could you talk to us a little bit about what makes a forest susceptible to fire, and how climate change might be affecting that?
Dr. Zach Zobel: Fire weather is a given set of atmospheric parameters that indicate—if there was an ignition source—fire would be able to grow and spread rapidly. What we do is we model what is known as the fire weather index. This index consists of four different atmospheric variables, and those are: temperature (the hotter it is, the more likely vegetation is going to dry out quicker); relative humidity (the lower the humidity, the more rapidly vegetation can dry out); precipitation, both backward looking (“has it rained a lot recently”) and today; and wind speed, because once a fire starts, if the wind is adequately high, that’s when it’s going to spread.
We take those variables out of the climate models, and we model it—what it looks like historically, versus what it’s going to look like in the future. And what we find is that in several fire regimes, most of them actually, these “high fire risk days” are starting to rapidly increase.
We see it especially in the Mediterranean, Brazil, eastern Australia, the Western United States, in several parts of Africa. Over the next 30 years, we think these high fire risk days are going to increase on the order of a couple of weeks in some locations like the Western US, to upwards of one to two months in the Mediterranean and Brazil. And that’s pretty significant, when you think about how historically these days only occurred maybe one week a year.
SR: So what are some of the risk outcomes posed by those more frequent, intense fires, globally?
BR: More frequent intense fires are changing the ecology of many boreal forests in some cases, leading to transition from forest to grassland or shrubland, which of course impacts the resident animals. But there are also large impacts on humans. The smoke from large wildfire seasons is a direct threat to human health, and rural and especially Indigenous communities often feel the largest impacts. Additionally, in areas of permafrost, which is ground that is frozen year after year, fires can lead to permafrost thaw for many years. That can often destabilize the ground leading to ground collapse, presenting a hazard to people that are living in these areas.
MM: I think the Amazon has many similarities with the Arctic, despite being very different environments. Despite not being natural, fires have become a recurrent issue that coincides with the dry season, which then creates what we call the burning season. Any fire is damaging to an environment that is not adapted to it. So there’s the immediate release of huge amounts of carbon when that biomass is burning, and there’s the delayed mortality that understory fires cause, so there’s continued emissions of carbon as well. That can cause a shift in species composition.
And fire also begets fire, which means that forest canopy that is disrupted allows more wind and sun to penetrate the forest, which creates drier microclimates. And tree mortality increases the fuels on the forest floor as well. So a degraded forest becomes even more vulnerable to future burning. As Brendon mentioned as well, there are several studies linking the burning season with higher hospitalization rates of people with respiratory illnesses as well.
SR: So, then what do these changes mean in terms of fire risk? How much of what we’re seeing now is on par with or accelerated compared to what climate models have been showing?
ZZ: Manu, and Brendan just hit it right on the head. What we’re seeing is the driver of these increasing high fire risk days, is largely because the length of the dry season is increasing in many of these fire regimes. Since they talked about the tropics and the Arctic, I’ll use California as an example. The dry season is typically from April to November or December. What makes California almost even more unique is that if this extends later and later into November and December, that’s when the Santa Ana winds start to pick up. So we found that that’s what’s happening in California, the wildfire season is expanding into later in the season. And that’s when their seasonal winds start, ahead of the rainy season.
In terms of risk to life and property, there’s also another factor that I think is a little underappreciated. (and this is happening in the Mediterranean and Australia and some of the major spots I talked about, maybe less so in Brazil, but Chile as well) is people are moving into areas that traditionally have had wildfires, even in the absence of climate change. And so, as we continue to build up property, let’s say in California, in the wildland urban interface as it’s known, that’s when you start to see things unfold, like we saw in 2019, in Australia and the Camp Fire as well in California.
When we talk with our partners, we always show them how rapidly the climate models are viewing this increase in fire weather days. We definitely caveat it by saying, Here’s what the observations are showing us. The climate models aren’t even keeping up with how quickly wildfire risk days are increasing. So we view it as is “this is the best-case scenario for the next 30 years.” And the best-case scenario is scary enough. And that’s kind of the message we send to the people that we work with when presenting this data.
SR: Not only do increased fires have immediate ecological and safety impacts. They also represent a significant risk to our ability to achieve climate goals. Forests are one of our most valuable carbon sinks, and keeping them healthy and standing is essential to curbing warming. Let’s talk a little bit about how fires pose a threat to that.
BR: So boreal forest fires release some of the largest amounts of carbon per unit area for any biome on Earth. And this is because most of the fuel is coming from the soil organic matter or Duff. And most of the climate impacts are from CO2 and methane. But actually, there’s a whole host of gases that are released into the atmosphere. And what’s worse, in areas of permafrost, those fires can induce permafrost thaw and degradation that can also release even more greenhouse gases over the ensuing years. This is what triggers the global feedback mechanisms from boreal fires—climate warming, leading to more fires, which leads to more net emissions of greenhouse gases that further fuels climate warming.
When we combine the carbon release estimates from intensifying fire regimes with the interactions between fire and permafrost thaw, the numbers are somewhat sobering. And they may impact our ability to meet the global temperature targets such as one and a half and two degrees above pre-industrial as set out in the Paris Climate Agreement. These impacts are largely not accounted for in climate models or remaining carbon budgets. So, one big question is what can we actually do about it?
I first want to stress that the fires themselves are not the cause of the problem. They’re a system response to warming. So ultimately, the solution is reducing and eliminating fossil fuel emissions that are warming our climate. That said, we do actually have some level of control over boreal fires through fire management control that we don’t have, for example, when it comes to other bigger system feedbacks. Our group has done some work to show that boreal fire management and specifically suppression of fires when they’re first ignited and relatively small, could be a cost effective way to keep carbon in the ground and protect against rapid permafrost thaw. Actually recently, for the first time, a land management agency in the US has adopted these ideas and designated land in Alaska to be protected from fire purely for the purpose of protecting permafrost and carbon. Of course, there are many, many considerations that come into play with changing land management, for example, the ecological impacts, and of course, the people that live on or near that land, including indigenous communities. So these are really complex decisions. But ultimately, as we’re hopefully headed down a path towards global net zero emissions, towards climate stabilization and eventual climate cooling. I think that limiting boreal fire emissions should be considered as a natural climate solution that also has many co-benefits for the habitat, for human health, and the economy.
SR: So Manu, is fire management also a potential solution for the Amazon?
MM: Um, I don’t think it’s a solution, I think is something that exists, but also kind of in tune with what Brendan was saying that fire is not the core of the issue. In the Amazon, deforestation is the major issue regarding climate change in general. So, this process of land grabbing and clearing for cattle ranching and cropland is the driver of deforestation and for as long as we have that, we will have these catastrophic fire events. These deforestation fires and the leakage that comes from that into forest areas, those are not things that firefighters can face with safety. These are intentional fires, and they’re part of the deforestation process. So, the path to ending these fires is through tackling deforestation. The other types of fires such as pasture fires, forest fires that are not in those areas of like frontier of deforestation, they can be dealt with through prevention and combat actions, such as preparing firebreaks ahead of the expected burning season, and having well trained, well equipped brigades ready for action. And that’s something that we’ve been trying to do as well. We’ve been providing GIS training to Indigenous fire brigades across the Amazon and developed some other partnerships as well with spatial analysis and trying to help out with science too, but the core issue is not fire it’s deforestation.
SR: So, combating fires and learning to manage them when they arise is important, as well as working with communities on the ground to do so. But the root cause of climate change lies in the vast amount of carbon emissions that are released by human activities. Ultimately, bringing fires under control will require mitigating emissions and curbing climate change, otherwise, forest fires might just become too hot to handle. Thank you, everyone, for sharing your perspectives on fire and climate change with us today.
Located in Eastern Alaska, the Yukon Flats National Wildlife Refuge is larger than many U.S. states. It’s a roadless landscape of rocky mountain outcroppings, flat meadows, treeless tundra, and dense spruce forests, bisected by the Yukon River and dotted with thousands of lakes and wetlands. Several Alaska Native communities call the refuge home and subsist off of its natural resources. This diverse, expansive wilderness is well adapted to fire, and it’s not uncommon to see pink fireweed blooms or young grass and seedlings sprouting from burn scars.
But the relationship between fire and land here—as in many places—has been changing as the climate warms. Yukon Flats sits atop ancient, ice-rich ground, called Yedoma permafrost, formed during the last ice age. Thawing Yedoma is a significant source of carbon dioxide and methane emissions to the atmosphere. Fire, made more intense and frequent by climate change, threatens to accelerate that thaw. In an effort to preserve carbon stores, the U.S. Fish and Wildlife Service recently dedicated 1.6 million acres of the Yukon Flats refuge to piloting a new firefighting regime, one designed to protect carbon, in addition to human lives and property.
This decision was, in part, influenced by research led by Dr. Carly Phillips, during her time as a research scientist at the Union of Concerned Scientists, alongside Woodwell Climate Senior Science Policy Advisor, Dr. Peter Frumhoff, and Associate Scientist, Dr. Brendan Rogers. In a 2022 paper in Science Advances, the group quantified the threat boreal forest fires pose to climate goals. Wildfires in boreal North America alone could, by mid-century, use up 3% of remaining global carbon dioxide emissions associated with keeping temperatures below the Paris Agreement’s 1.5°C limit. This is a conservative estimate—the authors suggest the true numbers could be even larger as the accelerating effect of fires on permafrost thaw, and the release of other greenhouse gasses, were not included in the analysis.
The study also examined the cost-effectiveness of combatting those fires as a potential climate solution. Molly Elder, an economics and public policy Ph.D. candidate at Tufts, performed an analysis of data from across Alaska’s fire management zones and found that actively suppressing boreal fires could cost less than 13 dollars per ton of carbon dioxide emissions avoided—putting it on par with other carbon mitigation solutions like onshore wind or utility-scale solar.
“The work we did in this project proved and quantified what the management community already knew, which is that management is effective at reducing burned area when fires are actively suppressed,” says Elder.
Combating boreal fires could provide much needed mitigation, and at a low cost, but there are some logistical obstacles between the hypothetical model and actual implementation. Typically, in Alaska, boreal forest fires are left to burn unless they present a risk to human life or property. This is partly because these forests are fire-adapted, but also partly due to the sheer vastness of boreal wilderness. With limited resources, it is not always practical or possible to track down and put out a fire, especially in a place without roads like Yukon Flats. Firefighters are already stretched thin with lengthening and increasingly high-intensity fire seasons.
So the research group worked with the fire management community in Alaska, facilitated by the Alaska Fire Science Consortium, to better understand the needs of firefighters and demonstrate the co-benefits of fire suppression in addition to preserving carbon.
“Many of the fire managers expressed how stretched their resources already were and resistance to the idea that yet another mandate would be added to their plate,” says Dr. Phillips. “However, after discussing the implications of our research, and the ambition that additional funding would come with any mandate, we got more buy-in.”
The other concern managers raised was whether fire suppression would ultimately be successful in achieving their goals. Historically, fire suppression efforts in the US have been counterproductive to protecting forests.
In the late 1800s, lack of understanding of the ways Indigenous communities in Western states have used fire to maintain healthy forests resulted in decades of near-total suppression of fire in the region. In many western US forests, (adapted to what Dr. Rogers calls “high-frequency, low-intensity” fire) suppression allowed highly flammable, dry vegetation—which would normally be periodically burned away—to build up. When fires did spark, they were then capable of growing to a size and intensity that could damage, rather than activate, the forest.
But in boreal Alaska and Canada, it’s just the opposite. The spruce-dominated forests are adapted to high-intensity fires that only return every hundred or so years. As climate change speeds up the return of fires with hotter and drier conditions, boreal forests have begun to suffer major losses.
“The frequency of boreal fires, ultimately, is increasing. In many places we’re seeing more reburning and larger burned areas,” says Dr. Rogers. “Climate change and human actions are shifting that fire regime out of its historical range into this new realm. So the whole idea of fire suppression in the boreal is to keep fires closer to historical levels, to which the systems and fauna are adapted. Suppression can help delay permafrost degradation, limiting carbon emissions and buying us time to reach our climate targets.”
Past missteps with fire suppression have made fire managers cautious, though. Lisa Saperstein, Regional Fire Ecologist with U.S. Fish and Wildlife, notes that, with limited resources, priorities in intense fire seasons will have to shift to protecting human settlements over carbon and permafrost. But, given the co-benefits of keeping fire activity to historic levels—and the urgency of reigning in emissions in any way we can—managers in Yukon Flats were willing to try.
“This type of shift in values is always difficult, especially when the outcome is uncertain. Support from leaders of fire management organizations, in addition to land managers, has been a key factor in this effort moving forward,” says Saperstein.
This change in tactics won’t mean that every fire that ignites will be put out—both impractical and unhelpful from an ecological perspective—but it will mean more aggressively targeting fires when they arise. Since the 1980s, when fire was detected in Yukon Flats, it would be monitored by the Alaska Fire Service, but not suppressed, except when presenting a threat to human communities.
“This pilot project is a new twist to a long-standing partnership between the U.S. Fish and Wildlife Service and Alaska Fire Service. For select areas of the Refuge, now if a fire start is detected, we ask the Alaska Fire Service to only send a crew if they are confident in 100% containment within three days,” says Yukon Flats Refuge Manager, Jimmy Fox.
The suppression teams will target fires that they judge as “quick fixes”, curbing the potential for them to grow into large, stand-replacing sized blazes. If a fire becomes too big to fight quickly, the teams revert to the old tactic of simply monitoring.
“If a crew is deployed, we ask that they cease suppression and return to base after three days, regardless of containment status,” says Fox. “This request is grounded in concern for the Alaska Fire Service having resources available if communities become threatened from other fires.”
Fox says refuge management and Alaska Fire Service members will stay flexible as the pilot project unfolds so they can respond to changing conditions.
“In conservation, we tend to focus on the technical aspects of a challenge and avoid the difficulties that come with asking ourselves to adapt,” says Fox. “This pilot project is both adaptive and technical. It has required me to stay curious and listen. It has required me to learn new information, and share it in a way that is comprehensible. It’s required being comfortable with uncertainty, and yet standing in purpose. It has been a learning journey so far, and will continue to be.”
On the research side, the team at Woodwell Climate hopes this new strategy will present an opportunity to study the practical implementation of fire suppression as a climate solution.
“This is the proof of concept,” says Dr. Frumhoff. “This is the opportunity to really see in a rigorous way whether we can apply this solution at a meaningful scale and gain meaningful carbon benefits with relatively modest cost. And it’s directly traceable to the conversations that the research team had with fire managers.”
The 1.6 million acres slated for fire suppression are small compared to the 8.6 million that comprise the entire refuge, or the 5.6 billion acres of permafrost in the northern hemisphere, but it’s a very important start. Research and analysis of the effectiveness of this solution could aid its expansion to other regions of the Arctic.
“It’s a big moment, because, while it’s obviously a relatively small area compared to all of Alaska, 1.6 million acres is still a lot of land,” says Dr. Rogers. “We’re hoping that it’s a jumping off point and can translate to other refuges and other agencies with the addition of proper funding and staffing.”
And each summer, the case for protecting permafrost and boreal carbon, while working to dramatically reduce emissions from fossil fuels, continues to grow.
“Every year that goes by, as fires intensify and climate change gets worse, this message might resonate just a little more, ” says Dr. Rogers. “Because it’s a problem that’s not going away if we do nothing about it. And we can do something about it.”
A recent paper offers new insight into the state of global forests. Using remote sensing imagery from MODIS satellites, researchers were able to categorize forest condition in two important biomes—the Amazon and the Siberian Taiga—differentiating between high stability, low stability, and non-forested areas. These “stability classes” provide another metric of assessing the conservation and carbon value of land, as high stability forests tend to be healthier, more resilient, primary forest stands that store large amounts of carbon and contribute to cooling the planet more than lower stability forests.
“Mature forests have higher biodiversity and create their own microclimate,” says paper co-author and Woodwell Associate Scientist, Brendan Rogers. “They’re more resistant to drought and other types of disturbance. And then because of that, they tend to be more stable in the face of environmental perturbations over time.”
To estimate forest stability, researchers analyzed satellite data that combined measures of photosynthetic radiation with a canopy water stress index. That new approach was able to identify whether or not a forest has been disturbed by either human land use (ex. logging) or natural processes (wildfire, insects outbreaks, etc.) and map the degradation level.
Co-author Dr. Brendan Mackey from Griffith University in Australia says that stability mapping is a first critical step in making an inventory of the world’s remaining primary forests which store more carbon, support the most biodiversity, and deliver the cleanest water.
According to Dr. Rogers, the less interruption in the ecological processes of the forest, the more secure the carbon stored in both the trees and soils are. Further human interference in an unstable forest could tip it into decline.
“I think one of the problems for primary forest conservation globally has been this idea that it’s either a forest or not a forest. So, internationally agreed upon definitions of what constitutes a forest sets a pretty low bar. You can get away with calling a plantation with very young trees a forest, but that could have been converted from a high biomass mature forest, and they’re simply not the same—not in terms of carbon, biodiversity, or ecosystem services,” says Dr. Rogers.
Using a gradient of forest stability instead of a black and white definition of forest/not-forest allows for more nuanced decision-making where both carbon monitoring and conservation planning are concerned.
“The first priority is to protect stable forests from further human disturbance, as once an area is deforested, it takes decades to centuries—and in some cases millenia—for it to regrow to a primary state. The second priority is to identify forest areas where restoration efforts will be most cost effective,” says Dr. Mackey.
According to the paper’s lead author, Dr. Tatiana Shestakova, this means places where a small investment could have bigger positive results.
“If you pick a forest that was degraded in some way, but it still keeps patches of more or less healthy forests, you can reinstate ecological processes faster and easier,” says Dr. Shestakova.
Dr. Shestakova said she encourages other researchers to apply the methods to their particular regions of expertise and expand estimates of forest stability globally.
“The benefit of this approach is that it was tested in such contrasting ecoregions, and has been proven to be a simple and efficient way to assess this important dimension of forest condition,” says Dr. Shestakova.
It was supposed to be a quiet season, but only two months into summer and Alaska is already on track for another record-setting wildfire season. With 3 million acres already scorched and over 260 active fires, 2022 is settling in behind 2015 and 2004 so far as one of the state’s worst fire seasons on record. Here’s what to know about Alaska’s summer fires:
Southwestern Alaska, in particular, has been suffering. The season kicked off with an unseasonably early fire near Kwethluk that started in April. Currently, the East Fork Fire, which is burning near the Yup’ik village of St. Mary’s, AK, is among the biggest tundra fires in Alaska’s history. Just above Bristol Bay, the Lime Complex— consisting of 18 individual fires— has burned through nearly 865,000 acres. One of the longest lasting fires in the Lime Complex, the Upper Talarik fire, is burning close to the site of the controversial open-pit Pebble Mine.
For Dr. Brendan Rogers, who was in Fairbanks, AK for a research trip in May, the explosive start of the fire season contrasts strongly to conditions he saw in late spring.
“It was a relatively average spring in interior Alaska, with higher-than-normal snowpack. Walking around the forest was challenging because of remaining snow, slush, and flooded trails,” said Dr. Rogers.
Early predictions showed a 2022 season low in fire due to heavy winter snow. But the weather shifted in the last ten days of May and early June. June temperatures in Anchorage were the second highest ever recorded. High heat and low humidity rapidly dried out vegetation and groundcover, creating a tinderbox of available fuel. This sudden flip from wet to dry unfolded similarly to conditions in 2004, which resulted in the state’s worst fire season on record.
The conditions for this wildfire season were facilitated by climate change, and the emissions that result from them will fuel further warming. The hot temperatures responsible for drying out the Alaskan landscape were brought on by a persistent high pressure system that prevents the formation of clouds— a weather pattern linked to warming-related fluctuations in the jet stream.
“With climate change, we tend to get more of these persistent ridges and troughs in the jet stream,” says Dr. Rogers. “This will cause a high pressure system like this one to just sit over an area. There is no rain; it dries everything out, warms everything up.”
The compounding effects of earlier snowmelt and declining precipitation have also made it easier for ground cover to dry out rapidly under a spell of hot weather. More frequent fires also burn through ground cover protecting permafrost, accelerating thaw that releases more carbon. According to the Alaska Center for Climate Assessment and Policy, the frequency of big fire seasons like this one are only increasing— a trend expected to continue apace with further climate change.
Additionally, this summer has been high in lightning strikes, which were linked to the ignition of most of the fires currently burning in Alaska. Higher temperatures result in more energy in the atmosphere, which increases the likelihood of lightning strikes. On just one day in July over 7,180 lightning strikes were reported in Alaska and neighboring portions of Canada.
The destruction from these wildfires has forced rural and city residents alike to evacuate and escape the path of burning. Some residents of St. Mary’s, AK have elected to stay long enough to help combat the fires, clearing brush around structures and cutting trees that could spread fire to town buildings if they alight.
But the impact of the fires is also being felt in towns not in the direct path of the flames. Smoke particulates at levels high enough to cause dangerously unhealthy air quality were carried as far north as Nome, AK on the Seward Peninsula.
“Even though a lot of these fires are remote, that doesn’t preclude direct human harm,” says Woodwell senior science policy advisor Dr. Peter Frumhoff.
Recent research has shown that combatting boreal forest fires, even remote ones, can be a cost effective way to prevent both these immediate health risks, as well as the dangers of ground subsidence, erosion, and loss of traditional ways of life posed by climate change in the region.
Mid-July rains have begun to slow the progression of active fires but, according to Dr. Frumhoff, despite the lull, it is important to keep in mind that the season is not over yet.
“The uncertainty of those early predictions also applies to the remainder of the fire season — we don’t know how much more fire we’ll see in Alaska over the next several weeks.”
A recent paper, published in Science Advances, has found that fires in North American boreal forests have the potential to send 3 percent of the remaining carbon budget up in smoke. The study, led by Dr. Carly Phillips, a fellow with the Union of Concerned Scientists (UCS), in collaboration with the Woodwell Climate Research Center, Tufts University, the University of California in Los Angeles, and Hamilton College, found that burned area in U.S. and Canadian boreal forests is expected to increase as much as 169 and 150 percent respectively—releasing the equivalent annual emissions of 2.6 billion cars unless fires can be managed. The study found proper fire management offers a cost-effective option, sometimes cheaper than existing options, for carbon mitigation.
Boreal forests are incredibly carbon rich. They contain roughly two-thirds of global forest carbon and provide insulation that keeps permafrost soils cool. Burned areas are more susceptible to permafrost thaw which could in turn release even more carbon into the atmosphere. Although fires are a natural part of the boreal ecosystem, climate change is increasing the frequency and intensity of them, which threatens to overwhelm the forest’s natural adaptations.
Despite the value of boreal forests for carbon mitigation, the U.S. and Canada spend limited amounts of funding on fire suppression, usually prioritizing fire management only where people and property are at risk. Alaska accounts for one fifth of all burned area in the U.S. annually, but it receives only 4 percent of federal funding for fire management. Limiting fire size and burned area through proper management can be effective at reducing emissions.
To prevent worsening emissions, fire management practices will have to be adjusted to not only protect people and property, but also to address climate change. Fire suppression in boreal forests is an incredibly cost-effective way to reduce emissions. The study found that the average cost of avoiding one ton of carbon emissions from fire was about $12. In Alaska, that means investing an average of just $696 million per year over the next decade to keep the state’s wildfire emissions at historic levels.
Increasing wildfires also pose an outsized threat to Alaska Native and First Nations communities, who may become increasingly isolated, and may lack the resources to evacuate quickly if wildfire encroaches on their lands. Many Alaska Native people already play a crucial role in existing wildfire crews, and investing in more fire suppression could create additional job opportunities for Indigenous communities.