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 Midwest can anticipate the following:
Northern and boreal tree species at the southern edge of their current range will decrease in abundance and extent as their current habitat becomes less suitable (and moves northward) and reestablishment in a warmer climate becomes more difficult. Some forested wetlands may disappear while oak and hickory species tolerant of low soil moisture may become more abundant.
Increased drought and fire occurrence are expected to have rapid and extensive effects on the structure and function of forest ecosystems. Oak decline and invasive species are expected to become more common.
Habitat connectivity and corridors for species movement will be reduced by increased disturbance and fragmentation.
Implementation of climate change adaptation will be challenging and outreach to private landowners will be necessary to ensure that climate preparedness is effective.
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