Key Findings from the U.S. Forest Service National Climate Assessment

A Message from Forest Service Scientists

Graphic image from the front of the national report on climate variability effects on U.S. forests. Graphic by U.S. Forest Service.
Graphic image from the front of the national report on the effects of climate variability on U.S. forests. Graphic by U.S. Forest Service.

U.S. Forest Service Research and Development recently published a comprehensive synthesis of the effects of climate change on U.S. Forests . Led and edited by Forest Service scientists Jim Vose (Southern Research Station), Dave Peterson (Pacific Northwest Research Station), and Toral Patel-Weynand (Forest Service Research & Development), the report includes chapters written by experts from federal agencies, universities, and nongovernmental organizations, and served as the primary technical input document in support of the 2013 National Climate Assessment conducted by the U.S. Global Change Research Program.

The Forest Service report examines bio-physical, social, and economic consequences of changing climate on forests, and discusses management options that could mitigate undesirable impacts and help forests adapt to climate change. Because climate change effects and management responses can vary regionally, the report includes a section that highlights regional impacts and issues. Key findings from the synthesis include:

Climate change will have significant impacts on the Nation’s forests and the ecosystems services they provide. While forests will be directly impacted by changing climate conditions such as warming, more variable precipitation, and elevated levels of carbon dioxide, the most significant and near-term impacts will occur from increased frequency and severity of disturbances such as insect outbreaks, wildfires, pathogens, and invasive species. Disturbances will often occur together, creating “stress complexes” that may have even greater effects than if disturbances occurred singly.

Although some regions in the U.S. will be more affected than others, the direct and indirect impacts of climate change are likely to change the structure and function of millions of acres of forest over a short period of time. Observations on how some forests have responded to climatic variability over the past few decades can be used to project future responses. Anticipated future impacts include increased tree mortality, changes in species assemblages, and changes in water resources from forested watersheds such as altered amount and timing of streamflow and reduced water quality.

Some of these changes may be unprecedented, perhaps creating novel ecosystems and environmental conditions that will challenge forest management. Not all changes will be negative; warming and higher levels of carbon dioxide may actually increase forest growth in areas of the U.S. where soil moisture and nutrients are plentiful.

Socioeconomic implications of the changes will vary across the U.S. due to differences in landownership patterns, vulnerabilities, and dependence on forest-based goods and services. Interactions among changes in biophysical environments and human responses to those changes will ultimately determine the consequences of climate-forest interactions to people. Rural, ex-urban and urban forests will differ in their responses. Populations in some areas may be more vulnerable due to current socioeconomic conditions that limit mobility or the capacity to adapt to or mitigate climate change impacts. Areas where economic welfare is more closely tied to forest-based goods and services will be affected the most by changing forest conditions. Private landowners are likely to respond faster to market forces and policies that encourage or discourage climate change-related management actions. Where public lands dominate, market forces may be less important as forests are managed for the broader public welfare.

Active forest management will be critical for minimizing impacts. Although uncertainty exists about the magnitude and timing of climate change on forests, sufficient information is available to help mitigate changes and help forest ecosystems adapt to climate change. The hallmark of successful management efforts has been science-resource manager partnerships that work collaboratively to develop adaptation and mitigation strategies and tactics. Indeed, land managers are already implementing “climate  smart” practices in many areas of the U.S.—for example, forest thinning to reduce climate driven wildfire severity—but more is needed, at larger spatial scales and directed at emerging multiple hazard problems. Given that forests already offset about 13 percent of the nation’s fossil fuel emissions, higher levels of integrated forest management could increase this number with more forests, faster growth of existing forests, and long-term storage of carbon in forest products. — Jim, Toral, and Dave, adapted from the May 30, 2013, Climate Update from the office of Dave Cleaves, Forest Service Climate Advisor  

On June 20, the Southern Research Station partnered with others to present a webinar on findings from the Forest Service national climate assessment. The webinar featured an introduction by Forest Service Climate Advisor Dave Cleaves, followed by discussion by authors Jim Vose and David Peterson. View the archived webinar now.

For more information, email Jim Vose at jvose@fs.fed.us.

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