USGCRP Global Climate Change Impacts in the U.S. - Agriculture

This report is one of seven sector-specific chapters from the United States Global Change Research Program's comprehensive 2009 report, "Global Climate Change Impacts in the U.S."  The 'Agriculture' chapter synthesizes current and projected impacts from climate change to agriculture in the U.S.  The chapter opens with a brief discussion of agriculture's impact on climate change.  The $200 billion U.S. agriculture sector accounts for 13.5 percent of all human-induced U.S. greenhouse gas emissions (8.6 percent of total U.S. greenhouse has emissions), including 80 percent of U.S. nitrous oxide emissions and 31 percent of U.S. methane emissions.  

The balance of the chapter focuses on the impact of rising temperatures on the agriculture sector, noting that increased agricultural productivity will be necessary in the future to keep up with rising population.  Particular emphasis is given to the impact on corn and soybean yeilds.  The chapter's key messages are that: many crops show positive responses to elevated carbon dioxide and low levels of warming, but higher levels of warming often negatively affect growth and yields; extreme events such as heavy downpours and droughts are likely to reduce crop yields because excesses or deficits of water have negative impacts on plant growth; weeds, diseases, and insect pests benefit from warming, and weeds also benefit from a higher carbon dioxide concentration, increasing stress on crop plants and requiring more attention to pest and weed control; forage quality in pastures and rangelands generally declines with increasing carbon dioxide concentration because of the effects on plant nitrogen and protein content, reducing the land’s ability to supply adequate livestock feed; and increased heat, disease, and weather extremes are likely to reduce livestock productivity.

A few adaptation strategies are suggested for the agricultural industry.  The report states that in some cases, adapting to climate change could be as simple as changing planting dates, which can be an effective no- or low-cost option for taking advantage of a longer growing season or avoiding crop exposure to adverse climatic conditions such as high temperature stress or low rainfall periods.  Another adaptation strategy described involves changing to crop varieties with improved tolerance to heat or drought, or those that are adapted to take advantage of a longer growing season.



Publication Date: June 2009

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