• About UANews
• Sign up for News
• Resources for Media
• Calendar
• Contact Us

The report details the effects of climate change on agriculture, land and water resources and biodiversity.

By University Communications
June 9, 2008

University of Arizona researchers contributed to one of the most extensive examinations of climate impacts on U.S. ecosystems, which was released recently by the U.S. Climate Change Science Program.

"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" integrated the federal research efforts of 13 agencies on climate and global change.

Steven Archer, UA professor in the School of Natural Resources, was the lead author on the Arid Lands section within the Land Resources chapter. Travis Huxman, associate professor of ecology and evolutionary biology and director of Biosphere 2, was a co-author on the Arid Lands chapter. David Breshears, UA professor of natural resources, was one of the reviewers of the report.

The report finds that climate change is already affecting U.S. water resources, land resources, agriculture and biodiversity, and will continue to do so.

"We are hoping this report reaches people in the land management agencies and policy makers, because they have to make decisions and planning projections for the next 30 to 50 years,” Archer said. “We also hope it is a good resource for educators who don’t have time to keep up with all of the literature.”

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 also will 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.
• Weeds grow more rapidly under elevated atmospheric carbob dioxide. Under projections reported in the assessment, weeds migrate northward and are less sensitive to herbicides.
• There is a trend toward reduced mountain snowpack and earlier spring snowmelt runoff in the western U.S.
• 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 carbon dioxide 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 be promoted by 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 also have shifted.

Arid lands are most prevalent in the West and Southwest and Archer cited the potential impact of climate change on water and air quality and water abundance in arid areas.

”If climate changes in the ways predicted, then there are potential significant consequences,” Archer said. “These lands support a large ranching industry, they contain a diversity of unique plants and animals and major airsheds and watersheds.”

Among the potential impacts in arid lands, according to Archer, are changes to the cover of vegetation and an increase in erosion – which may increase the frequency of dust storms in the West and Southwest.

Other possible impacts include an increase in wildfires, more water stress and promotion of non-native grasses. Arid lands will become more sensitive to and slower to recover from disturbances associated with grazing, fire and off-road vehicle use.

“The report intentionally does not provide recommendations,” Archer said, “but rather is an objective summary of what has already been reported in scientific literature.“

The report was written by 38 authors from universities, national laboratories, nongovernmental organizations and federal service. The report underwent expert peer review by 14 scientists through a federal advisory committee formed by the U.S. Department of Agriculture and a 45-day period of open public review. The National Center for Atmospheric Research helped coordinate the production of the report.