Climate change threat to US farming and biodiversity

Posted: 1 June 2008

Climate change is already affecting US water resources, agriculture, land resources, and biodiversity, according to a new US Government report.

Among the findings of the report, The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity in the United States: Forest fires are becoming more frequent and numerous, streams are warming, and the Mountain West is seeing much less snow.

Joshua tree, threatened by climate change
Joshua tree, threatened by climate change
Joshua tree of southern California, threatened by climate change. Photo © USGS
"The West and Southwest are likely to become drier, while the eastern United States is likely to experience increased rainfall," says the report, which was put out by the US Climate Change Science Program, coordinated by the White House. "We risk losing iconic charismatic megaflora such as saguaro cactus and joshua trees," co-author Steven Archer of the University of Arizona, Tucson, said at a press conference.

To generate this assessment of the effects of climate and climate change, the authors conducted an exhaustive review, analysis, and synthesis of the scientific literature, considering more than 1,000 separate publications.

Highlights of the report 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.
  • US ranching threatened by climate change
    US ranching threatened by climate change
    Traditional patterns of US ranching and farming are threatened by climate change. Credit: USDA
    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.
  • Horticultural crops (such as tomato, onion, and fruit) are more sensitive to climate change than grains and oilseed crops.
  • Invasion by exotic grass species into arid lands will result from climate change, causing an increase fire frequency. Rivers and riparian systems in arid lands will be negatively impacted.
  • The growing season has increased by 10 to 14 days over the last 19 years across the temperate latitudes. Species' distributions have also shifted.
    Monarch butterfly, threatened by climate change
    Monarch butterfly, threatened by climate change
    Monarch butterfly, threatened by climate change. Credit USDA
  • 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.
The report concludes that increased water use efficiency could help mitigate the impacts of climate change on water resources, and that better climate monitoring data is needed to provide accurate predictions of future effects.