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Title: Climate impacts on agriculture: Implications for forage and rangeland production

item IZAURRALDE, R - Pacific Northwest National Laboratory
item THOMSON, A - University Of Maryland
item Morgan, Jack
item Fay, Philip
item Polley, Herbert
item Hatfield, Jerry

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2010
Publication Date: 3/24/2010
Citation: Izaurralde, R.C., Morgan, J.A., Thompson, A.M., Fay, P.A., Polley, H.W., Hatfield, J.L. 2010. Climate impacts on agriculture: Implications for forage and rangeland production. Agronomy Journal. 103(2):371-381.

Interpretive Summary: Climate change is occurring around the world and the impacts of these changes on agriculture are causing concern about the potential consequences on grass and animal production. An analysis of the impacts of climate change on rangeland and forage crops was undertaken to document the expected impacts of rising temperatures and carbon dioxide over the next 30 to 50 years. This analysis also included the potential impacts of increasing variability in precipitation. Rangeland and forage species don’t exhibit the same response to rising temperature. The rising carbon dioxide levels are a positive benefit to plants and increase the efficiency of water use; however, this is offset by the rising temperatures increasing the rate of water use. The increasing ozone levels may cause more damage to plants than other stresses. In addition to the direct impacts of climate there are indirect impacts that result from increased weed, insect, and disease pressures because of the more favorable conditions for larger pest populations. There is a shift in the composition of rangeland species because some species respond more favorably to temperature and precipitation changes. Future food security will depend upon understanding the role of climate on rangeland and forage production and developing adaptive strategies to cope with these changes. This information will benefit scientists, policymakers, and educators about the role that climate plays in range and forage production.

Technical Abstract: Projections of temperature and precipitation patterns across the United States during the next 50 years anticipate a 1.5 to 2°C warming trend and a slight increase in precipitation. In general, the effects of climate change on crop species have been better studied than in pastureland and rangeland species, in spite of their comparable economic and ecological importance. The response of pastureland and rangeland species to climate change is complex because, in addition to the major climatic drivers (CO2 concentration, temperature, and precipitation), other plant and management factors will likely influence this response (e.g., community composition, plant competition, perennial growth habit, seasonal productivity, and management methods). In the United Sates, the geographic distribution of pasturelands and rangelands follows mostly precipitation distribution with the Mississippi River separating pasturelands to the east and rangelands to the west of its course. In general, the response of pasture species to elevated CO2 is consistent with the general response of C3 and C4 type vegetation to elevated CO2, although significant exceptions exist. Pasture species with C3-type metabolism increased their photosynthetic rates by up to 40 percent, but not those with a C4 pathway. The review revealed the need for comprehensive studies of the impacts of climate change on the pasture ecosystem including grazing regimes, mutualistic relationships (e.g., plant roots-nematodes; N-fixing organisms), and on the balance of carbon, essential nutrients, and water. Both pastureland and rangeland species should exhibit an acceleration of metabolism and development due to earlier onset of spring green-up and longer growing seasons. In general, it is expected that increases in CO2 concentration and precipitation may enhance rangeland net primary production (NPP) while increased air temperatures may either increase or decrease NPP. If, as currently predicted, annual precipitation changes little or declines in the southwestern United States, rangeland plant production may respond little to combined warming and rising CO2 and may even decline due to increased drought.