The Global Change Research Act of 1990 requires the U.S. Global Change Research Program (USGCRP) to produce the National Climate Assessment (NCA) for the President and Congress every four years, analyzing the effect of global change on multiple sectors and regions in the United States and projecting major trends forward for up to 100 years. Effects on Climatic Variability and Change on Forest Ecosystems: A Comprehensive Science Synthesis for the U.S. Forest Sector (PNW-GTR-870) serves as the U.S. Forest Service sector technical report for the NCA and includes descriptions of key regional issues and examples of a risk-based framework for assessing climate-change effects.
USFS researchers state that “projected changes in climate (temperature and precipitation means and extreme events), increased atmospheric carbon dioxide (CO2), and increased nitrogen deposition are likely to affect U.S. forests throughout this century. Effects will be both direct (e.g., effects of elevated CO2 on forest growth and water use) and indirect (e.g., altered disturbance regimes), and will differ temporarily and spatially across the United States. Some of these effects may already be occurring. For example, large insect outbreaks and large wildfires during the past decade (Bentz et al. 2009, Turetsky et al. 2010) are a wake-up call about the potential effects of a rapidly changing climate on forest ecosystems.
The Great Plains can anticipate the following:
- Tree species in mountainous regions are expected to gradually become redistributed to higher elevations, with disturbances mediating rapid change in some locations.
- Climate-driven changes in hydrology are expected to reduce the abundance of dominant, native, early-successional tree species and increase herbaceous, drought-tolerant, late successional woody species (including nonnative species) that will lead to reduced habitat quality for riparian fauna
- The potential for increased wildfire hazard, longer droughts, insect outbreaks, and fungal pathogens, individually and in combination, could significantly reduce forest cover and vigor.
Bentz, B.; Allen, C.D.; Ayres, M. [et al.]. 2009. Beetle outbreaks in western North America: Causes and consequences. Salt Lake City, UT: University of Utah Press. 44p.
Turetsky, M.R.; Kane, E.S.; Harden, J.W. [et al.]. 2010. Recent acceleration of biomass burning and carbon losses in Alaskan forests and peatlands. Nature Geoscience. 4:27-31.