On April 20, the Biden administration released a first-of-itskind inventory of mature and old growth forests on federal lands, as had been mandated by an executive order on Earth Day last year. The inventory is technically sound and identifies more than 112 million acres of mature and old growth forest on land managed by the Forest Service and Bureau of Land Management—more than previous analyses, which is great news. This is a necessary first step toward protecting these important forests, but there are critical gaps that must be addressed as protections are designed.
First and foremost, the carbon storage and climate mitigation power of these forests should be front and center, but both go largely unmentioned in the latest report. Federal forests absorb the equivalent of roughly 3% of US emissions from
fossil fuel burning each year, and mature and old growth forests are responsible for the majority of carbon uptake and storage. Multiple analyses by Woodwell Climate scientists and collaborators have found that the largest trees make up a small fraction of trees in a forest but store the majority of carbon. Furthermore, as intact forests mature, they accumulate even more carbon in soils.
In order to protect these mature and old growth forests, and the carbon and biodiversity they hold, we must identify the threats they face. The greatest threat facing national forests—and the one we most directly control—is logging; but here again, the latest report is largely silent. Instead, the focus is on warming-driven risks, especially fire. While it is vitally important to address climate risks, management actions to limit fire are not necessarily applicable in older forests. The body of evidence indicates that the best way to foster resilience to environmental disturbance, like fire, is to keep mature and old growth forests intact.
Further proposed rule-making and public comment opportunities are expected in coming days, and Woodwell Climate will be vocal in calling for protection of mature and old growth forests as the critical climate mitigation assets that they are.
A forest is a complex ecosystem, interacting with natural and anthropogenic forces in diverse ways. In the face of climate change, healthy, mature forests are some of the most resilient ecosystems on earth, providing crucial services and buffering against the worst effects of warmer temperatures, all while continuing to pull carbon out of the atmosphere.
Although younger forests sequester carbon at faster rates, older forests store more accumulated carbon in the wood and bark of trees, as well as continue to stow away carbon beneath the ground in plant roots and soils.
Mature forests are often more resiliant to large disturbances like fires. Older, more established trees—often having thick bark—are less likely to be killed in a blaze and a healthy forest can regenerate much more quickly than one that is already degraded. In the boreal region, where forests are adapted to fire, an area of burned forest regenerates quickly as seeds from nearby mature trees drop and sprout in the fertile ground.
Mature forests also provide important ecosystem services, especially the regulation of temperature and the filtration of water. Through the process of evapotranspiration, forests transport water vapor to the atmosphere, causing regional cooling, and preventing drought and vegetation dry-out that could make an area susceptible to fire or disease.
An established forest ecosystem is also a water treatment plant responsible for filtering out pollution from the watershed. Studies have shown even a small strip of forest along a body of water—called a riparian buffer—can prevent excess nutrient and sediment runoff from damaging the aquatic ecosystem.
What defines a “mature forest” is up for debate—age, tree diameter, and ecological stage all play a role in what makes a forest mature. One recent study led by researchers at Woodwell Climate assessed the maturity of 13 national forests in the United States using a combination of tree diameter and a metric called Culmination of Net Primary Productivity (CNPP), or the age at which tree canopy closure reaches 100% for a tree species.
We see the same headlines every year now. Fires—in the Arctic, in the Amazon rainforest, edging dangerously close to human communities. Forest fires play an important role in the climate change story—as both a symptom of warming temperatures and a cause of them. Woodwell Climate Science Writer, Sarah Ruiz, recently sat down with three of the Center’s leading experts on climate and fire to unravel that relationship— covering topics including the way fire differs between ecosystems, what is “fire weather,” how is climate change altering fire regimes, and how do we combat the issue to keep carbon locked away in forests and soils. Below is an excerpt from that conversation.
SARAH RUIZ 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, the term for it in fire science, often just takes 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, Manoela, 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
To hear the full interview and learn more about the fire management solutions the team at Woodwell Climate is working on, scan the QR code or visit woodwellclimate.org/ fire-and-climate-audio-story
above: Fire in the Pantanal region of Brazil. / photo by Manoela Machado
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, in 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, and 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. Aside from
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 emissions of carbon continue after a fire 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 How much of the fire headlines we have seen in recent years—the 2019–2020 Australian wildfires, the incredibly destructive Camp Fire in California—is on par with what fire weather models have shown?
ZZ When we talk with our partners, we always show them how rapidly the climate models are viewing this increase in fire weather days, but 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.” This is the best case scenario for the next 30 years, and the best case scenario is scary enough…
Increased fires not only have immediate ecological and safety impacts, they also represent a significant and growing risk to our ability to achieve our climate goals, which would bring fires back to a manageable level. Forests are one of our most valuable carbon sinks and keeping them healthy and standing is essential to curbing warming.
In a world plagued by rapid change and challenges, many of us are asking the question: “How can I help?” As individuals, it can be hard to find a way to give back and help steward the natural resources we rely on. But, for those who love fly fishing—anglers—Science on the Fly offers a path to do just that.
Science on the Fly engages the enthusiastic and passionate fly-fishing community, in the U.S. and abroad, as citizen scientists. Members of the fly-fishing community have close relationships with their local rivers—from having a favorite fishing hole, to knowing the seasonally anticipated flows of the river and when certain bugs are hatching. They are also more aware than most people of the impacts of climate change on local fisheries. In states like Colorado
above: Allie Cunningham on the Science on the Fly raft on the shores of the Kanektok River. / photo by Andrea Norton
For four years, Science on the Fly has nurtured a community science network to study distant rivers.
Director of Science on the Fly
and Montana, anglers have given up the opportunity of even casting a fly rod at some points in the summer season. Why? The trout are too stressed and lethargic due to the droughts and rising water temperatures.
Fly-fishing citizen scientists are excellent resources for data collection and observation of climate trends to create a clearer picture of how rivers are changing over time. With their help, the number of rivers subject to long-term studies of water quality and watershed health can be increased. Since Science on the Fly
In Woodwell Climate’s environmental chemistry lab, the samples are analyzed for concentrations of nutrients such as nitrate, phosphate, silica, ammonium, dissolved organic carbon, and total dissolved nitrogen. All data is shared publicly, and after a year’s worth of data has been collected, a report is written on the state of the river for those sampling locations.
This project got to where it is extremely quickly. A year after the program was founded, it had grown from two citizen scientists to 140 enthusiastic river
Science on the Fly is now exploring how best to integrate its water quality sampling and citizen scientist model with Woodwell Climate’s important research in the Alaskan Yukon-Kuskokwim Delta region. Located at the lowest section of the permafrost belt, this region is experiencing rapid thaw as the climate warms. Could water quality collection be done in a way that tells the story of the rivers over time? Could anglers floating down these remote rivers provide samples in a timely manner? The answers found are yeses, but it has taken some practice to get there, and the region presented unique challenges that haven’t encounter in other regions.
The Science on the Fly core team now rafts, researches, and fishes vulnerable and wild rivers in this region—including the Arolik, Kanektok, Kisaralik, Kwethluk, and the Goodnews—each summer season. Each morning of the trip, the teams gear up and take a variety of samples and water quality measurements—including the collection of 60 mL sterile river water samples. Water temperature monitoring sensors are also installed or retrieved in the watershed, which provide river temperatures from the entire year. Some samples collected during the trips are used directly for the Science on the Fly program, while others help collect data for different research projects associated with Woodwell Climate or other organizations.
was founded in 2019, data on nutrients and organic compounds has been collected from over 350 river sites across the United States each month.
The science collection process is straightforward and easy. Sample locations are chosen for their accessibility and interest to fly-fishing volunteers, who are responsible for collecting a small bottle of sterile river water from each location once a month, as well as data on air and water temperature. They then freeze the bottles and bulk ship them back to Woodwell Climate Research Center one or two times a year.
activists. Over the course of four years, more than 7,000 bottles have been placed into the hands of empowered citizen scientists.
It is easy to see how the program got here so fast; when a free tool-kit is offered to the passionate angler that can help them give back to their watershed, they want to get involved. While a kit isn’t necessarily cheap to put together, at a cost equaling $100 per bottle, it is an extremely effective way to add novel data to the climate science dataset on many watersheds—information that wouldn’t otherwise be gathered.
These research trips are only answering some questions, however. Data on the rivers’ nutrient concentrations throughout the summer season would also help answer questions—not just when team members are there for ten or fewer days a year per river. Like most science, it’s not inexpensive. It’s also not easy to logistically coordinate a river research trip—all the gear, travel, food, science supplies, safety equipment, and qualified team members to float—from afar.
above: Science on the Fly notebook and sampling equipment. / photo by Ryan DelaneyPapaBear Adventures in Bethel, Alaska has solved the logistics coordination challenges. PapaBear is an operation that helps the adventurous outdoors person get to the headwaters of remote rivers, and gives them the tools they need to float the rivers on their own. They have been instrumental in meeting the transportation needs of other Woodwell Climate projects like the Polaris Project, and now they are helping Science on the Fly get anglers out to the rivers throughout the summer season.
Beyond working with PapaBear on transportation, Science on the Fly now stations a team member—Joe Mangiafico or Allie Cunningham, for now—at PapaBear for the summer months. This team member preps the research team’s trips, making sure they are properly prepared to go down the rivers with all materials needed. But the main goal is to encourage other PapaBear clients and their groups to be involved in the
sampling. Pre-made kits are handed out to groups floating these rivers. After the groups get off the rivers, a Science on the Fly team member retrieves the filled sample kits and freezes them for shipping back to Woodwell Climate.
The data that has returned from these endeavors is already exciting.
In summer 2021, the Science on the Fly research team sampled two rivers, the Kwethluk and Kisaralik, and by a lucky ask to some passing groups of anglers, the Kanektok and Goodnews Rivers were sampled as well. There were a total of 45 samples collected that summer. The following summer, the combination of Science on the Fly research teams and new efforts to increase engagement with volunteer citizen science groups, allowed an increase of collections to 248 sample bottles. Data collection on the other rivers of the Yukon-Kuskokwim Delta were successfully increased, and the Arolik
Dr. Sue Natali was interviewed about permafrost and global climate on Climate Now’s podcast, published both on their website and on Apple podcasts.
Darcy Glenn was interviewed on KPCW this week about the Summit County Department of Health’s Climate Change and Public Health speaker series, where she presented on Woodwell Climate’s risk assessment for the county.
On Earth Day, Dr. Peter Frumhoff was interviewed about solar geoengineering to address climate change by CBS News Saturday Morning (timestamp 12:20).
Dr. Linda Deegan was interviewed by CAI’s Mindy Todd on local STEM opportunities for young women.
Dr. Sue Natali was interviewed on ESRI’s TikTok channel about what makes her optimistic about the future of climate action.
CNN chronicled the harassment that meteorologists and climate communicators face, including Dr. Jennifer Francis, from conspiracy theorists.
Yale School of the Environment published an article to celebrate award-winning doctoral research, co-authored by Dr. Nigel Golden.
was added to the list. The hope is to accomplish even more in years to come.
Four years of Science on the Fly has shown that citizen scientists and citizen science programs can be a powerful way to collect data, conduct research, and educate the public through our reports. Now that a solid project structure has been built, with data coming in consistently, there is beginning to be more focus on making an impact with report writing and affecting policy—all while continuing to add to the growing body of water and climate science. Citizen-collected data will be used to create tangible reports for anglers to better understand their watersheds. These reports will then be used to help make an impact on policies, with the goal of creating or maintaining healthy watersheds, especially in the face of climate change. Science on the Fly looks forward to continuing to give back to citizen scientists and to the rivers.
Cape Cod Times noted that the cranberry bog restoration led by Massachusetts Audubon Society, in partnership with Woodwell Climate and other local organizations, will receive $4.3 million in federal climate change grants.
ABC News quoted Dr. Zach Zobel in a widely syndicated article on water allocation in California.
Dr. Christopher Schwalm was quoted in a Toronto Star article on the growing fear of food insecurity in Canada.
Dr. Jennifer Francis provided the climate context for a CBS News article covering Cyclone Mocha’s impacts in Myanmar.
BNN Bloomberg interviewed Dr. Brendan Rogers about how fire season across the boreal north is getting longer.
Mongabay quoted Dr. Marcia Macedo on fire in the Amazon. The story was also published in Mongabay Brazil (Portuguese).
An article from IPAM noted that a collaborative policy brief on Amazon forest degradation was delivered to Brazil’s Ministry of the Environment and Climate Change; the brief came out of a workshop last month supported by Woodwell Climate (Portuguese).
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