Scientists from Woodwell Climate Research Center are among the 195 leading experts in forest ecosystems, climate change, and the carbon cycle who have come together to urge the Biden Administration to immediately declare a moratorium on all logging in mature and old-growth forests on federal lands. The signers include seven members of the National Academies of Sciences and some of the most notable names in climate science.
The letter comes amid growing concerns within the scientific community around the U.S. Forest Service and Bureau of Land Management’s response to an executive order, issued by the Biden Administration on Earth Day 2022, to establish guidelines and best practices to safeguard mature and old-growth forests on federal lands. The letter was initiated by Dr. Beverly Law, Professor Emeritus at Oregon State University, and Dr. Bill Moomaw, Professor Emeritus at Tufts University and Distinguished Visiting Scientist at Woodwell Climate. Last week, Woodwell Climate Senior Scientist and signatory Dr. Rich Birdsey delivered the letter’s message to the Mature and Old Growth Science Summit, hosted by the Forest Stewards Guild, the U.S. Forest Service, and the Society of American Foresters.
“Old-growth forests are made up of our oldest, and typically largest, trees that store massive amounts of carbon,” said Dr. Rich Birdsey. “We need to protect old growth, as well as younger mature forests that can attain old-growth characteristics with time.”
“The carbon storage function these forests play is essential to our efforts to reduce carbon emissions and mitigate the impacts of the rapidly changing climate, yet millions of acres of mature and old-growth forests stand on federal lands that are vulnerable to logging,” said Dr. Beverly Law. “To align with the United States’s commitments to ending global forest deforestation and degradation, we must urgently halt any additional logging of these critical natural resources.”
The scientists point to recent efforts by the agencies to increase timber sales and logging of these forests rather than increasing their protection as directly contrary to these objectives, and call on President Biden to issue a new executive order prohibiting activities that further forest degradation in the short-term, while the Administration works, in partnership with policy and climate leaders, to develop and implement effective, long-term management policies. Reducing timber harvesting of carbon-dense forests can have an immediate effect of lowering emissions and is the most significant action that the U.S. can take to immediately limit greenhouse gasses.
“With their 2022 executive order to protect mature and old-growth forests, the Biden Administration laid the groundwork for the U.S. to emerge as a global leader in conserving these forests and making good on international climate commitments,” said Dr. William Moomaw. “Halting logging in the interim is necessary to protect these resources now, while also working with the agencies to develop strong, long-term policies consistent with the Administration’s commitments to addressing climate change and safeguarding forests as a natural climate solution.”
The full letter can be found here.
Woodwell Senior Scientist Dr. Rich Birdsey has contributed his decades-long expertise in forestry and climate issues to two new U.S.-based forest policy initiatives. Working on both the state and federal level, Dr. Birdsey is helping to expand the influence of science in policy planning.
Federal forest policy
On July 20, Woodwell Climate submitted a response to the U.S. Forest Service’s request for public input into how they can adapt current policies and develop new ones to support the conservation of the country’s forests and increase their resilience in the face of climate change. The push for new rulemaking within the agency is a direct response to President Biden’s recent executive order: Strengthening the Nation’s Forests, Communities, and Local Economies.
Protecting forests is a crucial emissions mitigation strategy both within the US and globally. Forests, particularly mature and old-growth stands, contain centuries-worth of stored carbon and continue to sequester more each year. Loss of these precious forests releases stored carbon and reduces future carbon sequestration.
In the public comment, Dr. Birdsey, who led the drafting effort, emphasizes the importance of protecting mature and old-growth forests, stating, “When climate benefits are explicitly considered, the research points strongly to letting these forests grow—protecting and expanding the massive portion of sequestered carbon they represent. One of the largest threats facing mature and old-growth forests in the US is logging, which is a threat that humans can reduce instantly, simply by changing policy.”
Forest protection on the state level
Dr. Birdsey has also been named a scientific expert on a committee charged with helping draft Massachusetts’ forest policies. A new state initiative, called “Forests as Climate Solutions” looks to expand existing forest conservation activities and develop new forest management guidelines that can help Massachusetts meet its climate goal of achieving net-zero greenhouse gas emissions by 2050. The science committee will be responsible for providing input into the state’s proposals and assessing their effectiveness as climate solutions.
“Forests have to be at the forefront of our climate strategy,” said Massachusetts Climate Chief Melissa Hoffer. “Trees can sequester carbon for centuries—we have a responsibility to use the best science to ensure that their potential for carbon sequestration and storage is reflected in our approach.
Dr. Birdsey’s hope is that the policies developed by the new initiative will help Massachusetts take full advantage of its naturally carbon-rich forests.
“Massachusetts forests have some of the highest carbon stocks in the Eastern U.S., and I hope that policies enacted through this initiative will strengthen protection of older forests and large trees and foster management of younger forests to attain old-growth characteristics, while maintaining the current level of timber supplies,” says Dr. Birdsey.
Both policy initiatives present an important opportunity to set forest management on the right track towards achieving emissions reductions in years to come.
“Massachusetts’ forests have the potential to accumulate and store enough additional carbon to compensate for as much as 10% of the State’s current emissions from burning fossil fuels,” says Dr. Birdsey. “With climate-smart forests, Massachusetts can be a national climate leader.”
On April 20, 2023, the U.S. Department of the Interior (DOI) and Department of Agriculture (USDA) released a first-of-its-kind inventory of the country’s mature and old-growth forests. The assessment responded directly to a 2022 executive order aimed at fostering healthy forests.
The inventory highlights the importance of forest health in building resilience to future climate-related disturbances like drought or fire, but it omits mention of the service that all forests, but particularly mature and old growth forests, provide in directly mitigating the country’s carbon emissions—a service that Woodwell Climate’s scientists have worked to measure and monitor for over three decades.
The inventory is a critical starting point, from which agencies like the U.S. Forest Service and the Bureau of Land Management will begin to make decisions about how public forests are managed going forward. Not acknowledging the critical carbon storage contribution of mature and old-growth forests runs the risk of de-prioritizing protection for the country’s oldest, most carbon-rich, and hardest to replace ecosystems.
Why protect mature and old-growth forests?
In short: carbon. While all forests sequester carbon as they grow, older and larger trees represent an existing store of carbon in their biomass and soil. Research by Woodwell Climate scientists on carbon stocks in a sample of federally managed U.S. forests found that while larger trees in mature stands constitute a small fraction of all trees, they store between 41 and 84 percent of the total carbon stock of all trees.
An analysis of mature and old growth forests across the country found that approximately 76 percent (20.8 million hectares) of these forests are unprotected from logging. This represents an amount of carbon roughly equivalent to 1 quarter of the US’s annual fossil fuel emissions.
Although younger forests grow faster proportionally, they are not adding as much carbon in a single year as older forests with large trees. Additionally, mature forests continue to pack away carbon year over year in their soils, which is largely protected from effects of disturbance. Cutting down a mature forest creates a “carbon debt” that can take decades—centuries in some cases—to recoup, and in the meantime those mature trees are no longer sequestering carbon each year.
“Forests are like naturally occurring factories, delivering to the planet the unique service of carbon sequestration. Trees of all sizes, but particularly large old trees, are the equivalent of warehouses where the goods produced—tons of carbon—are stored over time,” says Woodwell Climate Carbon Program Director, Dr. Wayne Walker. “Like any warehouse where valuable goods are stored, these natural carbon reserves deserve all the protection we can provide. Their loss could effectively bankrupt our efforts to avoid the worst impacts of climate change.”
Defining mature and old-growth forest
Protecting mature forests requires them to be identified and mapped, which was part of the impetus behind the government’s forest inventory. But what actually is a mature forest?
Definitions of “mature” and “old-growth” differ, with no one universally accepted definition. Refining scientific understanding of what constitutes a mature forest has implications for either expanding or reducing the area of forest considered for protection.
In one study of U.S. forest carbon stocks, Woodwell Climate researchers and collaborators outlined a measure of forest maturity based on both the age that the tree canopy in a forest becomes 100 percent closed, called “Culmination of Net Primary Productivity,” and tree diameter size. Across 11 U.S. forests analyzed, the age at which a forest is considered mature ranged from 35 years in Appalachian forests to 75 in Arizona. “Old-growth” represents a smaller subset of mature forests having older and larger trees.
The new inventory from the DOI and USDA uses a slightly narrower definition of maturity, wherein the lower bound occurs when regeneration has begun underneath the canopy. This results in a slightly smaller estimation of the amount of mature and old-growth forests in the US—yet still approximately 63 percent of the total area of federally managed forests.
Other definitions can be based on models that take into account measurements of forest structure like canopy height, canopy cover, and biomass. Another study, co-authored by Woodwell Climate Assistant Scientist, Dr. Brendan Rogers, used these features to determine that federal lands contain the largest concentration of the country’s mature and old growth forests.
Differences in those definitions are important, because forest policy debates surrounding the responsible management of these forests depend on adequately identifying them, particularly mature forests, which are much more loosely defined than old-growth.
“I think the discussion is almost more about what to do with mature forests, as opposed to old-growth,” says Woodwell Climate senior scientist, Dr. Richard Birdsey, who worked in the U.S. Forest Service for four decades. “Mature forests are at a younger stage of growth—trees would be smaller, although they could still be substantial in size and very profitable to harvest. So the question here is whether to let those forests grow into old-growth characteristics, or to start harvesting them for wood products.”
What do we do with our mature forests?
When climate benefits are explicitly considered, the research points strongly to letting these forests grow—protecting and expanding the massive portion of sequestered carbon they represent.
According to Dr. Birdsey, the largest threat facing mature and old-growth forests in the U.S. is logging, which is a threat that humans can reduce instantly, simply by changing policy. A change that would make those forests more resilient to other threats in the long run.
“Others might argue that climate change or wildfire are more significant threats,” says Dr. Birdsey. “Older forests with larger trees are more resistant to those threats—but not more resistant to chainsaws. That’s a human decision.”
A recent paper in Nature Climate Change has laid out a “protect, manage, restore” framework for making decisions about what natural climate solutions to pursue, and the highest priority is always to protect carbon where it is already stored. U.S. policies have made some recent progress in this direction through the enforcement of the roadless rule on Alaska’s Tongass National Forest, prohibiting road-building and industrial logging on the 9 million acre temperate rainforest. But there is still further to go to capitalize on the carbon storage potential of the U.S.’s mature forests.
Federally managed forests contain more high-carbon trees than other lands, so the opportunity for increased carbon storage within them is greatest. Woodwell Climate Distinguished Visiting Scientist, Dr. William Moomaw, helped coin the term “proforestation” to refer to the strategy of letting forests continue to grow as a carbon solution. In order to achieve that, he says, mature forests have to be protected.
“The next steps should be to provide legal protection of as much of these high-carbon forests as possible,” says Dr. Moomaw. “These are public lands that should serve the public good, and reducing climate change is a public good that we should pursue as the highest priority.”
