The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity

The U.S. Global Research Program report “Synthesis and Assessment Product 4.3 (SAP 4.3): The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity in the United States ” integrates the Federal research efforts of 13 agencies on climate and global change.

The report has 38 authors from the universities, national laboratories, non-governmental organizations, and Federal service. SAP 4.3 has undergone expert peer review by 14 scientists through a Federal Advisory Committee formed by the USDA, and includes over 1,000 references. USDA was the lead agency for this report as part of its commitment to USGCRP.

The report focuses on the next 25 to 50 years, and finds that climate change is already affecting U.S. water resources, agriculture, land resources, and biodiversity, and will continue to do so. Links to specific sections of the report, Q&As, and more information are listed in the right column.

SEE ALSO

National Climate Assessment

U.S. Global Change Research Program

SPECIFIC FINDINGS INCLUDE:

• Grain and oilseed crops will mature more rapidly, but increasing temperatures will increase the risk of crop failures, particularly if precipitation decreases or becomes more variable.

• Higher temperatures will negatively affect livestock.  Warmer winters will reduce mortality but this will be more than offset by greater mortality in hotter summers.    Hotter temperatures will also result in reduced productivity of livestock and dairy animals. 

• Forests in the interior West, the Southwest, and Alaska are already being affected by climate change with increases in the size and frequency of forest fires, insect outbreaks and tree mortality. These changes are expected to continue.

• Much of the United States has experienced higher precipitation and streamflow, with decreased drought severity and duration, over the 20th century.  The West and Southwest, however, are notable exceptions, and increased drought conditions have occurred in these regions.  

• Weeds grow more rapidly under elevated atmospheric CO2.  Under projections reported in the assessment, weeds migrate northward and are less sensitive to herbicide applications.

• There is a trend toward reduced mountain snowpack and earlier spring snowmelt runoff in the Western United States. 

• Horticultural crops (such as tomato, onion, and fruit) are more sensitive to climate change than grains and oilseed crops.

• Young forests on fertile soils will achieve higher productivity from elevated atmospheric CO2 concentrations.  Nitrogen deposition and warmer temperatures will increase productivity in other types of forests where water is available.

• Invasion by exotic grass species into arid lands will result from climate change, causing an increased fire frequency.  Rivers and riparian systems in arid lands will be negatively impacted.

• A continuation of the trend toward increased water use efficiency could help mitigate the impacts of climate change on water resources.

• The growing season has increased by 10 to 14 days over the last 19 years across the temperate latitudes.  Species’ distributions have also shifted.

• The rapid rates of warming in the Arctic observed in recent decades, and projected for at least the next century, are dramatically reducing the snow and ice covers that provide denning and foraging habitat for polar bears.