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Frequently Asked Questions
Effects of Climate Variability and Change on Forest Ecosystems

A U.S. Department of Agriculture Technical Report

1. What is the Effects of Climate Variability and Change on Forest Ecosystems Report?
The USDA peer-reviewed scientific report reviews the projected consequences of climate change on the forests of the U.S.  The consequences described include the biological impacts on the nation’s forests—both privately owned forests and public lands—and associated economic and social impacts.   The report evaluates current conditions, looks ahead the next 25 to 100 years at potential consequences on the forests and their users, and identifies potential adaptation strategies.  Written by experts from Federal service, universities, and non-government organizations, the report draws on more than 1,000 scientific citations, expanding and updating the information published in SAP 4.3: The Effects of Climate Change on Agriculture, Land Resources, Water Resources and Biodiversity in the United States.

This report was developed in support of the National Climate Assessment (NCA).  The 2013 NCA is being prepared in response to the Global Change Research Act of 1990 (GCRA). 

2. What are some of the report’s findings?
Future changes in forests will occur on both public and private lands.  The ability of forests to provide essential services, such as clean drinking water, outdoor recreation, and quality wildlife habitat, will change, especially as populations grow and demands for these services increase.  In some locations, the quality or quantity of these services will decline, while in other areas, they may also improve or expand.  Some areas may be particularly vulnerable to changes because current conditions are the result of past climates and economic conditions, and those will be changing in the next 100 years.

Climate changes are also expected to change the pattern, frequency, and intensity of disturbances.  The result will be increased wildfires, doubling the area burned annually by the mid-21st century.  Insect infestations are expected to continue to expand; the recent expansion of bark beetles in the western U.S. and Canada is a forerunner of these kinds of changes.  Pulses of soil erosion and flooding caused by higher rainfall intensity will increase, but the pattern will be highly variable.  This will also affect how forest roads are built and maintained, along with other infrastructure.  Some places will see the opposite impact—increased droughts—which will cause other stresses on forest health and productivity, and secondarily, insect and disease outbreaks and wild fires.  The result will be higher tree mortality, slower regeneration after disturbances, and changes in the species of trees in the areas affected.

3. Will snowfall and winter sports be affected, as well?
Yes, changing climate will also influence not only summertime rainfall, but winter snows as well.  Decreased snow cover will make the moisture deficit in some forests worse, which may further decrease tree vigor and increase susceptibility of forests to insects and diseases.  Less snow will also translate into shorter seasons for winter sports, such as skiing and snowmobiling.  And less snow will mean less spring-time runoff, lower water storage levels in reservoirs, and less water available for crop irrigation.

4. What other effects are anticipated for U.S. forests?   
Climate change projections suggest increased variability in temperature and precipitation.  Extreme events including dry spells, sustained droughts, and heat waves, can have large effects not only on forests, but on the wildlife and fish living in them and on the people that use forests.  Further, the quality of life in rural communities will be affected.  For example, a community that depends on forest streams for high quality drinking water may see summertime flows reduced or need to add more pre-treatment if increased soil erosion from heavy rains muddy the water.  Tourism will decline if forests die from bugs or wild fires and employment in forest products mills may decline or disappear if healthy forests disappear.  Some of these impacts will extend well beyond the rural communities to touch the lives of people in cities far removed from the forests.

5.  Can U.S. forests help slow the rate of climate change? U.S. forests already store enough carbon to offset about 13% of the Nation’s CO2 emissions from fossil fuels.  Where soil moisture is sufficient and tree-killing disturbances are not widespread, forests will continue to accumulate and store carbon.  However, large disturbances such as wildfire or insect outbreaks, or loss of forest cover to other land uses, will reduce the ability of forests to sequester carbon.  Increasing carbon storage to help slow the rate of climate change will require active management to increase forest area or avoid forest loss; increase net carbon storage in existing forests; and use of wood as biomass energy in place of fossil fuel or use in long-lived wood products for C storage as a substitute for fossil fuel-intensive building materials, such as steel or concrete.

6. Can U.S. forests adapt to changing climate?

Yes, but not without the help of forest managers and support of the American public.  U.S. forests have successfully adapted to changing conditions since the 1880s when coal replaced wood as the primary domestic, industrial, and transportation fuel.  Although the U.S. population has nearly tripled, cities have grown, and farming has changed dramatically since then, the area of forests in the U.S. has changed less than 5 percent and forests have continued to provide essential services.  But the keys to our success for the past 130 years have been the increase in our scientific understanding of forests and the benefits they provide and public support for active management of forests to meet emerging and future needs.   Some forests are already being managed using “climate smart” practices, but much more will be needed —more science and more active management—to help forests adapt successfully to climate changes in the coming 100 years. Resource managers in the USDA Forest Service are already engaged in a wide range of sustainable forest management practices (e.g., reducing hazardous fuels, maintaining structurally diverse forests) that improve resilience to future climate stresses.

7. What is USDA doing about climate change? 
USDA is using the report’s findings to develop adaptation strategies and technical advice for forest owners and managers that support decision-making under changing conditions.  The Research & Development arm of the Forest Service conducts research into the anticipated effects from climate change and evaluates adaptive strategies that increase resilience of forests.  The Foreign Agricultural Service sponsors scientific exchange programs to support climate change objectives.  The Forest Service is involved on multiple fronts on maximizing carbon storage over the long-term.  The Farm Service Agency manages programs which help to diminish atmospheric greenhouse gas concentrations while achieving other environmental benefits.  The National Institute of Food and Agriculture supports climate objectives through research, education, and extension services.  The Natural Resources Conservation Service provides financial and technical assistance to help agricultural producers become more resilient to climate change and reduce greenhouse gas emissions.  And USDA’s Risk Management Agency has developed tools to assist with the management of limited irrigation water supplies during water shortages.