USDA releases report summarizing impact of climate change on U.S. ecosystems

COPENHAGEN, Denmark, Dec. 14, 2009 -- The U.S. Department of Agriculture, in cooperation with the University Corporation for Atmospheric Research and the U.S. Global Change Research Program, released a new report at the climate talks in Copenhagen, Denmark...

COPENHAGEN, Denmark, Dec. 14, 2009 -- The U.S. Department of Agriculture (USDA), in cooperation with the University Corporation for Atmospheric Research and the U.S. Global Change Research Program (USGCRP), today released The Effects of Climate Change on U.S. Ecosystems today at the climate talks in Copenhagen, Denmark.

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"Climate change poses significant threats and challenges for farmers, ranchers, and those who make a living off the land, which will have a serious impact on our ability to feed the people of the United States and the world," said Vilsack. "President Obama has made climate change one of his top domestic priorities and under his Administration, the United States has done more to reduce greenhouse gas emissions than at any other time in history, both by supporting domestic policies that advance clean energy, climate security, and economic recovery; and by vigorously engaging in international climate negotiations. "

The report provides an accessible summary of findings contained in a U.S. scientific assessment project commissioned by the USGCRP and released in May 2008. New information has been added to provide additional detail on the original findings.

Based on a wealth of source and review literature, the report concludes that climate change is already affecting U.S. agriculture, land resources, water resources, and biodiversity, and will continue to do so. The report identifies the effects climate is having and is expected to have on natural resources and ecosystems services in the U.S. over the next several decades, including:

• Climate change has had an impact on American farmers, ranchers, rural land owners, and foresters, and will continue to do so, through its influence on production, distribution, and yields.
• Although the report does not reflect the economic consequences of these effects on production, economic implications are inescapable due to the dependence of productivity on climate, both directly (through changes in temperature and precipitation) and indirectly (through the effects of climate on pest outbreaks, weed distribution, water supplies, changes the nutritional content of forage due to elevated CO2, and so on, that in turn influence production).
• Grain and oilseed crops will mature more rapidly, but increasing temperatures will heighten the risk of crop failures, particularly where precipitation decreases or becomes more variable.
• Marketable yield of horticultural crops (such as tomato, onion, and fruit) are more vulnerable to climate change than grains and oilseed crops due to the high sensitivity of their quality and appearance to climate factors.
• Livestock mortality will decrease with warmer winters 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, due to changes in consumption and lower pregnancy rates.
• Weeds that can thwart agriculture production grow more rapidly under elevated atmospheric CO2, extend their range northward, and are less sensitive to herbicide applications.
• Disease and pest prevalence will escalate as a result of shorter, warmer winters, challenging crop, livestock, and forest systems.
• The trends toward reduced mountain snowpack and earlier spring snowmelt runoff in the Western U.S., and toward increasing drought in the West and Southwest, imply changes in the availability of water and a need to monitor the performance of reservoir systems with implications for water management and irrigated agriculture in that region.
• Climate change is inducing shifts in plant species in rangelands, favoring the establishment of perennial herbaceous species that reduce soil water availability early in the growing season. Shorter winters, however, decrease the need for seasonal forage reserves.
• Forests in the interior West, the Southwest, and Alaska are already being affected by climate change as demonstrated by increases in the size and frequency of forest fires, insect outbreaks, and tree mortality over large areas.


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