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New study identifies mature forests on U.S. federal lands ripe for protection

This photo of logged old-growth forest outside Olympia National Park, shows what can happen when mature forests aren’t given full protection.

This photo of logged old-growth forest outside Olympia National Park, shows what can happen when mature forests aren’t given full protection. Image by Justin Catanoso for Mongabay.

  • A new mapping study conducted by NGOs finds that older forests in the U.S. make up about 167 million acres, or 36%, of all forests in the contiguous 48 states. About a third of this, or roughly 58 million acres, are on federal lands. The rest are controlled by non-federal entities, including large amounts held by private owners.
  • Just 24% of U.S. Forest Service and Bureau of Land Management forests are fully protected, with the rest being at various levels of risk from logging, offering the Biden administration an opportunity to more thoroughly protect far more old-growth and mature forests on federal lands in order to help meet U.S. climate goals.
  • The new study identified a challenge inherent in this strategy: The majority of federal lands are in the West, but one of the highest concentrations of U.S. mature and old-growth forests is in the Southeast, where most older forests are on private property. Privately held old-growth and mature forests are poorly protected in the U.S.
  • If the U.S. wants to broaden its carbon emission reduction strategy, say researchers, then mature forest conservation should include both federal and private holdings. Private forests could be protected via state regulation, utilizing conservation easements and payments for verifiable carbon offsets, along with land trust acquisition.

In a major new study, a team of scientists has published what it calls the first-ever, map-based assessment of existing mature and old-growth forests in the continental United States. Such forests are critical to fighting climate change and data like this is deemed vital to President Biden’s climate action agenda.

But the new research also shows how much mature forests on both federal and private lands in the U.S. are seriously at risk — offering a conservation opportunity to the Biden administration.

The peer-reviewed study, published in Frontiers in Forests and Global Change, found that older forests — estimated to be 80 years old or older — make up about 167 million acres, or 36%, of all forests in the contiguous 48 states.

The new study included this map generated by researchers showing mature and old-growth forests by region across the U.S. Image courtesy of Dominick DellaSala / Wild Heritage.

Significantly, about a third of those older forests, or roughly 58 million acres, are on federal lands managed by the U.S. Forest Service (USFS), the Bureau of Land Management (BLM) and the National Park Service (NPS). The rest are controlled by non-federal entities, including private owners.

The research noted that even though U.S. national parks are fully protected from logging, just 24% of U.S. Forest Service and Bureau of Land Management forests are similarly protected, with the rest being at various levels of risk. The study calls for all mature and old-growth forests on federal lands to become fully protected.

The researchers say that those needing protection range in age from 80 to 150 years old or older — with some of those federal forests being actively logged now. The scientists based their estimates on the structural characteristics of the biodiverse forests mapped.

In addition, the researchers urged that mature forests on private lands be eligible for some form of protection through state regulatory agencies using incentives, payments for carbon offsets, and other preservation techniques.

Globally, forests and their vegetation remove about a third of human-produced greenhouse gases from the atmosphere annually, slowing the rate of global warming via what has been dubbed nature-based climate solutions. But those forests only sequester carbon if they remain intact and healthy — filled with a diversity of plants, animals, insects, and soils rich with fungi.

Old-growth forest along a highway on the Olympic peninsula in Washington state. The nation’s mature forests need deeper protections on both federal lands and private lands if the U.S. is to implement wide ranging forest nature-based climate solutions, say researchers. Image by Sam Beebe found on flickr.

Western old-growth on federal lands at risk

Generations of coast-to-coast development, logging, wildfires, and climate change-induced impacts have dramatically reduced the nation’s older forests, threatening wildlife and diminishing the nation’s air quality and climate resiliency.

“Our study confirms the outsize role that the nation’s older forests play in addressing the climate and biodiversity crises,” said Dominick DellaSala, the paper’s lead author and chief scientist with Wild Heritage, an NGO and environmental advocacy group in Oregon.

One significant finding, he said, is that some 50 million acres of older federal forests, mostly in the West, are imminently vulnerable to logging.

Those forests — described as “low-hanging fruit” for priority protections — store the equivalent of 10.6 gigatons of carbon dioxide, the study found, which if logged over 10 years, would release the equivalent of 9% of U.S. annual greenhouse gas emissions.

Redwood trees in California. Iconic species including redwoods and giant sequoias are fairly well protected. But the new study calls for a wide range of mature and old-growth forests on federal lands to become fully protected. Image by Rhett A. Butler / Mongabay.

President Joseph Biden has made climate action a priority of his administration. In two executive orders, he directed agencies responsible for federal lands, including the Departments of Interior (which includes BLM) and Agriculture (which includes USFS) to develop strategies to protect 30% of U.S. land and waters by 2030, known as the 30 by 30 Plan, to which 94 other nations have agreed.

Biden also ordered those agencies to complete an inventory of mature and old-growth forests by April 2023 as a tool for creating new protections to keep carbon sequestered and help the nation meet its Paris Agreement pledge of reducing U.S. emissions by 50-52% over a 2005 baseline, also by 2030.

“Protecting older forests from logging on federal lands is critical to President Biden’s plans to reduce emissions by 2030,” said DellaSala, whose independently conducted study is meant to complement the federal inventory not replace it. “By avoiding emissions from logging, carbon is retained in the forest and not sent into the atmosphere, which would increase global warming and climate impacts.”

The U.S. is currently the second-largest emitter of greenhouse gases at 13.5% of global emissions behind only China at 30.6%.

A tree farm in the U.S. Southeast. Pine plantations like this one are harvested on 20-year cycles. Tree farms support little biodiversity, offer few ecological services, and have limited carbon storage capacities compared to mature and old-growth forests. Photo credit: National Forestry Center on Visualhunt.

Demonstration and accountability

DellaSala, joined by seven other scientists in completing the study, said the old-growth inventory has been a goal of his for more than a decade. Technological advances in remote monitoring made the study possible now with what he deemed “a high degree of confidence.”

The scientists combined NASA satellite imaging for U.S. forest canopies with flyover LiDAR data, which can ‘see through’ the treetops and produce 3D models of a forest, its canopy, undergrowth, and under certain conditions, the forest floor itself. The team then overlaid land maps and consulted with regional forest experts in interpreting their results.

To create their findings, they evaluated three structural measures relevant to forest maturity — canopy height, canopy cover and above ground living biomass in trees and vegetation

Importantly, the study found that “at the stand level, old-growth forests store 35% to 70% more carbon, including in soils, than [planted] stands.” It noted also that old-growth forests can act as natural buffers to extreme climate conditions, providing watershed protections and wildfire resilience.

DellaSala noted that tree farms were easily identified and excluded from the study’s mature and old-growth statistics. Tree farms typically consist of monocultures of a single tree species. They harbor little biodiversity, store less carbon than mature forests, and offer scant ecosystem services. They’re planted by timber interests for harvest on regular rotations, providing lumber, paper products, and woody biomass for U.S. use and abroad.

The researchers shared their findings with officials from federal agencies in Washington who are in the process of completing a similar inventory for President Biden, to be available by April 2023.

“Our work shows what’s possible to do with spatial mapping and bottom-up analyses,” said Brendan Rogers, study co-author and an associate scientist with the Woodwell Climate Research Center in Massachusetts. “At the very least, we can hold the agencies accountable for their results and see that they are not easily circumvented by special interests.”

In a statement to Mongabay, the USFS responded to the publication of the new study on behalf of itself and the Departments of Agriculture and Interior:

“The Forest Service appreciates the public comments received regarding the criteria needed for a universal definition framework that motivates mature and old-growth forest conservation and can be used for planning and adaptive management. That definition will be key to inventorying mature and old-growth forests.”

A study map showing current distribution of 182 forest and woodland ecosystem types as categorized under the International Union for Conservation of Nature (IUCN) Red List of Ecosystems. Nearly all these ecosystems include mature and old-growth forests. Image courtesy of Dominick DellaSala / Wild Heritage.

Southeast mature forests on private lands vulnerable

The new research underscored a potential regional weakness in the U.S. strategy to protect mature forests that is focused primarily on federal lands, a concern also identified by forest advocates not connected to the study. The concern: the largest amounts of protected federal lands often don’t match up with where most mature forests are located.

For example, while there are 154 U.S. National Forests, most are in the Rocky Mountain states and farther west. Only 20 are in the Southeast, where 90% of wooded land is privately held and is largely unprotected. But one of the highest concentrations of U.S. mature and old-growth forests is in the Southeast.

Today, canopy cover and carbon storage capacity in the Southeast is steadily being eroded as the region’s private lands are aggressively logged for development, timber, wood and paper products, and increasingly, wood pellet manufacture for energy generation in overseas markets.

No federal laws and few state-level regulations stand in the way of the demise of the Southeast’s mature forests on private lands — a valuable carbon sink and hedge against climate change.

Lucia Ibarra, director of conservation for the Dogwood Alliance in North Carolina, an NGO not involved in the study, said that if mature trees are to be saved in the Southeast, then additional old-growth forest conservation incentives must be developed for private land owners there. Otherwise, she said, private logging could continue intensifying in the region, even as federal land protection efforts expand.

DellaSala said he shared those concerns. The study team notes that on non-federal lands, a combination of state-level regulatory improvements and incentives could be implemented to better protect privately held forests and benefit land owners. Some examples cited are conservation easements, land trust acquisitions, and payments for verifiable carbon offsets.

The Biden plan to conserve mature forests “needs to be comprehensive at the federal and state levels,” DellaSala said. “Federal lands are the anchor point, but unless it’s comprehensive, you won’t hit the 30 by 30 targets.”

Wood pellet manufacturing is a major growth industry in the U.S. Southeast. The pellets, often sourced from whole trees, are exported to Europe and elsewhere where they’re burned to make energy in former coal power plants. There are no regulations to prevent the forestry industry from cutting old-growth and mature forests on private lands. Image by #ODF on VisualHunt.

Problematic new legislation

Meanwhile, forest advocates like DellaSala and his colleagues are expressing concern over new forest legislation introduced by U.S. Senators Joe Manchin (D-West Virginia), and John Barrasso (R-Wyoming), that they say could undermine and derail federal old-growth protections before they can even be put in place.

The proposed legislation claims that it “aims to restore ecosystems and boost carbon storage and sequestration through tree planting, fire risk reduction projects, and expanded use of forest products and new wood technologies.”

But Blaine Miller-McFeeley, a senior legislative representative at Earthjustice, an NGO, said in a statement, that the law would do otherwise: “This bill misinforms the public instead of protecting it. The bill will benefit the logging industries, not communities or the climate.”

Harvesting old-growth timber near Soquel Mill, California in 1901. Pre-colonial North American forests were a wonder of the world, but centuries of logging greatly diminished mature U.S. forests. President Biden has said he wants to preserve what’s left on federal lands. Image source Johnston, Hank (1968). Thunder in the Mountains: The Life and Times of Madera Sugar Pine. Stauffer Publishing. p. 10. ISBN 0-87046-017-X. Image in the Public Domain.

DellaSala explained further, noting that, “Manchin and Barrasso say it’s all about protecting against fires. The problem with that argument is that the trees most resistant to fire are in our mature and old-growth forests. [But the senators] want to actively cut old-growth and plant new trees, which is insane.

“Look, the President has very aggressive emission-reduction goals,” DellaSala said. But “he’s not going to get there by only reducing emissions from the energy and transportation sectors. You have to enlist the land sector to close the emissions gap, not by logging old-growth forests, which will only add to emissions, but by protecting them.”

Justin Catanoso, a regular contributor to Mongabay, is a professor of journalism at Wake Forest University in North Carolina. Follow him on Twitter @jcatanoso

Banner image: An expanse of legally clearcut forest inside a U.S. National Forest in Washington state. While national park forests are fully protected, just 24% of U.S. Forest Service and Bureau of Land Management forests are fully protected, with the rest at various levels of risk. Image by Justin Catanoso.


DellaSala DA, Mackey B, Norman P, Campbell C, Comer PJ, Kormos CF, Keith H and Rogers B (2022) Mature and old-growth forests contribute to large-scale conservation targets in the conterminous United StatesFront. For. Glob. Change 5:979528. doi: 10.3389/ffgc.2022.979528

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Old-growth and mature forests aren’t only important to protecting Earth’s climate; they also conserve biodiversity. Image courtesty of the Forest Service Alaska Region, USDA via Flickr.
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