Temperature, length of growing season, atmospheric CO2 levels, water availability, pests, disease, and extreme weather events can all affect crop growth and yields to varying degrees—and sometimes in conflicting ways—depending on location, agricultural system, and the degree of warming. For example, growth of some heat-loving crop plants such as melons and sweet potatoes will initially respond positively to increasing temperatures and longer growing seasons in the United States. Other crops, including grains and soybeans, respond negatively, both in vegetative growth and seed production, to even small increases in temperature. Many crop plants, such as wheat and soybeans, respond positively to the fertilization effect of increases in atmospheric CO2, potentially offsetting some of the negative effects of warming.
In the United States, many northern states are projected to experience increases in some crop yields over the next several decades, while in the Midwest and southern Great Plains, temperature increases and possible precipitation decreases may decrease yields unless measures are taken to adapt. Likewise, global-scale studies suggest that
For additional discussion and references, see Chapter 10 in Part II of the report.
moderate warming of 1.8°F to 5.4°F (1°C to 3°C), increases in CO2, and changes in precipitation could benefit crop and pasture lands in mid- to high latitudes but decrease yields in seasonally dry and low-latitude areas. Projections also suggest that global food production is likely to decrease with increases in average temperatures of greater than 5.4°F (3°C). However, most analyses and projections of future climate change do not include critical factors such as changes in extreme events (especially intense rainfall and drought), pests and disease, and water supplies, all of which have the potential to significantly affect agricultural production.
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