Encouraging health and longevity of our forests may require crossing the “comfort zone” of forest management.
Young plantation thinning — or removal — is a widely accepted practice to restore structure to a forest and encourage biodiversity by managing tree density, age or species. These efforts take a tonal shift into muddied territory when the thinning potentially involves mature stands, a classification generally applied to giants that are 150 years old.
However, such measures may be necessary to address vulnerabilities exacerbated by climate change in a portion of the Gifford Pinchot National Forest, according to Jessica Hudec, a regional U.S. Forest Service ecologist.
“We are confident that we’re going to have more frequent droughts, which leads to increased stress, pests, pathogens and an increased susceptibility to this rapid acceleration of fire that’s expected in the coming decades,” she said.
The Forest Service drafted considerations to commercially thin 7,100 acres of mature and transitional forest in the Little White Salmon watershed, which sits at the national forest’s lower eastern edge. The project also includes commercially thinning roughly 6,900 acres of young forest plantation and the non-commercial thinning of up to 1,600 acres, according to scoping documents.
The impetus for this management is twofold: mitigate fire risk and build resiliency for forest health, Hudec said.
Poking at mature stands is a touchy subject. Proponents urging for the trees to be left alone marvel at the aged giants as silent witnesses of history, as well as crucial players in keeping ecosystems happy.
In short: it’s complicated.
A nuanced conversation
One early afternoon in late September, project leads and members of the South Gifford Pinchot Collaborative — a collection of environmental and timber groups, state and federal agencies, local governments and the public —meandered between tree trunks, both young and old, taking in bits of the watershed’s characteristics. The trip is one of many meetings with stakeholders to fine-tune project considerations.
Several locations on the tour illustrated varying degrees of complexity in mature thinning.
Some mature stands show signs of laminated root rot, a disease that will eventually wipe out the trees it infects. Sites throughout the watershed have competing priorities, such as protecting northern spotted owl habitat despite there being an absence of the owls. Other areas showed that the costs of removing mature trees don’t outweigh the benefits — they won’t be touched.
During the watershed trip, some attendees lamented at the suggestion of removing mature trees, like those that towered over them, contending that mature stands are critical for capturing carbon from the atmosphere.
While this is true, Hudec added, there is a limit to how effective retaining older trees are in a broader land management sense. Additionally, retaining younger stands can aid in their progression toward becoming older forest.
“We need to look at the landscape as a whole and have a multi-tiered approach to carbon uptake and building complexity into the landscape,” she said.
Cascade Forest Conservancy, a nonprofit focused on the Gifford Pinchot National Forest, generally doesn’t recognize any value of removing mature stands, said Ashley Short, the group’s policy manager. While old forests are essential for ecological processes, they are rare and difficult to replace, especially considering negative climate trends, she added.
“We like to look at each stand and its justification instead of making a blanket recommendation,” she said in an interview after the site trip. “We don’t have the information on what the justification is for each of those older stands, so conversations need to be had.”
Planning ahead
The idea of thinning mature forest is indicative of the complexity of management on the landscape under review and fire itself, Hudec said.
A majority of the Gifford Pinchot National Forest’s 1.32 million acres is westside forest: full of dense Douglas fir stands, mixed with Western hemlock and redcedar. They stand among carpets of thick, green vegetation teeming with biodiversity.
In the Little White Salmon watershed, roughly 68,660 acres, the land begins to deviate from that western standard. The Cascade Range splices through the watershed, splicing forest into two varied landscapes. On the west, the expanse is relatively wet while the east is dry.
The Washington Department of Natural Resources listed the watershed as a priority landscape in its 20-year Forest Health Strategic Plan, which outlines treating between 21 percent to 32 percent of forested acres – which mostly apply to eastern portions of the watershed.
Officials say it will likely be among the first areas within the Gifford Pinchot National Forest to face stressors caused by climate change, prompting them to consider the range of actions to keep pace with this transformation. Old forests are not immune to an onslaught of droughts, rather they are particularly threatened by the warm and dry conditions, Hudec said.
Talk around thinning mature stands is just that — a conversation to gauge how the Forest Service’s plans will take shape. Acreage considerations have not been solidified and will likely change before the project’s approval.
As an example, President Joe Biden’s Executive Order 14072, signed in April 2022, requires land management agencies to inventory mature forests and prioritize the preservation of these stands in forest plans, among other protective actions. Forest Service planners said they will likely reduce the Little White Salmon’s 7,100 acres under consideration for mature thinning to comply with the order.
Experts attempt to understand whether a site can continue to have a certain density or composition of stands by using a mix of metrics and climate scenarios, helping guide their considerations, Hudec said. However, discussions with stakeholders will also inform what alternatives to include in the project’s environmental analysis.
Collective members will continue to examine the Forest Service’s project considerations leading up to the creation of the agency’s environmental analysis, slated to be drafted as early as late spring in 2024 and subject to public comment. Officials expect to make a decision later that year.
