Beyond reforestation, let’s try ‘proforestation’

Edward Faison, an ecologist at the Highstead Foundation, stood quietly in a patch of forest that stretched for miles in all directions. Above him, the needles from white pine trees swayed — common in the Adirondack Forest Preserve in northern New York state. He stepped past downed wood and big, broken snags, observing how the forest functioned with minimal interference.

“These forests have been essentially unmanaged for over 125 years. To see them continue to thrive and accumulate carbon, recover from natural disturbances and develop complexity without our help reveal just how resilient these systems are,” Faison says.

Protected from logging in 1894 by an act of the New York Legislature, the Adirondack Forest Preserve (AFP) is a model of natural forest growth, or letting forests simply “get on with it.” The largest trees, white pines (Pinus strobus), are more than a century old and stretch more than 150 feet tall and are 4-5 feet in diameter.

The AFP, the largest wilderness preserve in the eastern United States, is a prime example of what researchers have come to call “proforestation.” Coined in 2019 by Tufts University professor William Moomaw and Trinity College professor of applied science Susan Masino, the term proforestation describes the process of allowing existing forests to continue growing without human interference until they achieve their full ecological potential for carbon sequestration and biological diversity.

Proforestation is considered a natural climate solution, i.e., a strategy to steward the Earth’s vegetation to increase the removal of carbon dioxide (CO₂) from the atmosphere. According to Faison, a forest naturally develops greater complexity over time, with a diversity of tree sizes and heights as well as large standing dead trees and downed logs. This complexity provides habitat for various animals, plants and fungi, which make the forest more resilient to disturbances associated with climate change.

Proforestation is distinct from reforestation, which can involve planting new trees in deforested areas to restore them (or allowing deforested areas to naturally regenerate). It is also different from afforestation, which is the process of planting new forests in previously unforested areas. Proforestation’s merit lies in inaction: simply leaving old forests undisturbed, allowing for continuous growth to maximize carbon accumulation over time. As forests mature and trees grow larger, they sequester greater amounts of carbon.

“The largest 1% diameter trees in a mature multiage forest hold half the carbon,” according to Moomaw. “It’s the existing forests that we have that are doing the work.” Existing forests remove almost 30% of CO₂ from the atmosphere that humans put in every year from burning fossil fuels.

Older is better

In Mohawk Trail State Forest in Massachusetts, Moomaw studied the tallest grove of white pine trees in New England, aged between 150 and 200 years, observing how the trees grew. When comparing them with younger trees of the same type growing under similar conditions, he found that “the amount of carbon added by these trees between 100 and 150 years of age is greater than the amount added between zero and 50.”

In addition to carbon storage capabilities, old forests are pivotal in controlling regional and global water cycles through a process called evapotranspiration, by which water is transferred from the land to the atmosphere. Due to deeper and more complex root systems as well as larger canopies and leaves, old forests capture more water and release it as vapor into the atmosphere.

“Old forests have the genetic competence to do this work,” Masino says. “It’s not done by meadows. It’s not done by grassy areas. It’s not done as effectively by forests that have been cut or planted. It’s these ancient systems that have the complexity to bring water to themselves. And in doing that, they’re bringing it to the rest of the landscape. Once you start cutting the landscape, you’re drying it out.”

Masino, who also has a joint appointment in neuroscience and psychology at Trinity College, emphasizes the importance of designating natural areas appropriately and allowing more room for proforestation.

“It’s urgent to decide where we intend to prioritize natural processes, where we are doing research, and what areas we are dedicating for our resource needs,” she says. “Nature needs room to breathe. We can’t leave everything open to manipulation and extraction. It’s deadly.”

She says that planting trees on streets, on campuses or in parks is good for temperature regulation, flood protection and creating habitat, but these trees don’t grow up in a web of life. Planting trees in a forest, too, can risk disrupting the dynamic complexity of evolved and evolving genetic knowledge.

Wildlife dependent on old growth

Over on the West Coast, University of Oregon professor emeritus Beverly Law has studied forests for decades. She describes watching three logging trucks, each with a giant log from an old, single tree strapped to the back, passing in a procession while waiting at an intersection on her bike, a frequent occurrence on her way to work at the university in the late 1980s.

“There are plant and animal species that rely on these old forests for their survival. You take away the forest, and they’re gone,” Law says. “It’s important to have diverse genetics in the forest. Some of them will be more genetically able to withstand climate change than others. You don’t know which ones they will be. That is why genetic diversity within species is important.”

Mature forests are crucial to the survival of certain critically endangered animals that rely on the connected canopies or the soil-rich forest floor. Preserving the biodiversity of the Pacific Northwest, which hosts forests more than a thousand years old, is especially dire. According to a 2022 paper published in Environmental Chemistry Letters, old growth forests retain a number of species from both the top and bottom of the food chain, such as the Olympic salamander (Rhyacotriton olympicus), the Del Norte salamander (Plethodon elongatus) and the two species of tailed frog (Ascaphidae). Losing them forever could kick off a cascade effect and result in severe consequences for the environment.

The spotted owl (Strix occidentalis), too, depends on old-growth forests in the Pacific Northwest, requiring the specific environment for roosting and nesting, and remains a central figure in forest management debates.

Such hulking ancient trees are the eyes of the woods, having stood through changing years and the changing climate.

“Ten to 12% of old-growth forests are left [in the US], and it’s insane that people are still trying to cut them down,” Law says. “They are the only survivors of American handiwork. Is it man’s dominion over the forest? We should have reverence, considering they’re all that’s left.”

Banner image: Pine cone of a white pine (Pinus strobus). Image by Denis Lifanov via Flickr (CC BY-NC-SA 2.0).

How the U.S. got no old growth forest protections from the Biden Administration (commentary)

Citation:

Gilhen-Baker, M., Roviello, V., Beresford-Kroeger, D., & Roviello, G. N. (2022). Old growth forests and large old trees as critical organisms connecting ecosystems and human health. A review. Environmental Chemistry Letters, 20(2), 1529-1538. doi:10.1007/s10311-021-01372-y

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Jeremy Hance Editor

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