New threats from increased area, density and layering of forests, climate change, shifting wildfire regimes, and invasive species in forest landscapes east of the Cascade Range have triggered a need for new management policies. USDA Forest Service photo.
Large and old trees are important landscape elements. Given the complexity of changing climatic and wildfire regimes, as well as social and economic considerations, land managers are evaluating whether protecting many of these critical trees may require moving beyond one-size-fits-all restrictions like the 21-inch rule. Part of the larger set of Eastside Screens, this rule prohibits the harvest of any trees, regardless of age or species, greater than 21 inches in diameter. This standard has been in place in the eastern portion of the Pacific Northwest Region since 1995.
The rapidly changing conditions of forests in eastern Oregon and southeastern Washington create a need to adapt management policies. Prompted by new threats from climate change, shifting wildfire regimes and invasive species, a new context for management has emerged since the 21-inch standard was first applied. How forests respond to such disturbances has changed dramatically because of many factors, including the exclusion of fire and past management activity.
In response, the Forest Service Pacific Northwest Region is preparing to amend six land management plans for the Umatilla, Wallowa-Whitman, Malheur, Ochoco, Deschutes, and Fremont-Winema National Forests.
Earlier this year, Regional Forester Glenn Casamassa asked the Pacific Northwest Research Station to prepare a rapid review and synthesis of the science related to the 21-inch standard. In response, the station brought together a diverse group of scientists who completed the review in 45 days. The paper’s key findings summarize scientific advances and socioeconomic changes that have occurred over the last 25 years.
The report makes the case that the 21-inch standard does not account for evolving forest development trajectories and ongoing relationships with fire and climate, nor does it offer adequate flexibility to make site-specific management decisions. Not all big trees are equal, nor are big trees always old.
"Tree diameter alone is an insufficient guide for restoration, or for adapting landscapes to climate change, insect outbreaks and changing wildfire regimes," explained PNW research landscape ecologist Paul Hessburg, one of the report authors. “Research suggests that simply protecting large trees misses key nuances, which compels us to ask, ‘Where should fire-tolerant and intolerant old forests and large trees live on the landscape? And what should their relationship be with environmental settings?’” In other words, ‘what do climate and wildfire adapted forest patchworks look like?’
“The question of whether to adapt the 21-inch standard is as much a social as an ecological one,” said social scientist Susan Charnley, a co-author of the report. “Public trust is critical because of the history of old-growth harvesting that was unsustainable on federal lands in the past,” she said. “If management actions are not socially acceptable or culturally sensitive, they will likely be more controversial.” Effective public engagement and tribal consultation will be critical for forging trust in the decision-making process.
The regional office and research station staff have also partnered to design an effective and efficient monitoring program to support adaptive management if the proposal is adopted. In addition, they worked together to gather relevant Forest Inventory and Analysis data, consult on data trends, and host a science forum that engaged more than 100 stakeholders.