Climate Change Is Bad News for U.S. Agriculture

Eli is a contributing correspondent for Science magazine.

A landmark review of over 1000 papers documenting ecological change in the United States has found that a shifting climate is affecting agriculture, biodiversity, and land and water resources from the mountains of Alaska to the sands of Death Valley. Among the findings of the report, released yesterday: Forest fires are becoming more frequent and numerous, streams are warming, and the Mountain West is seeing much less snow. More changes may be coming, especially for U.S. farmers and ranchers.

"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 U.S. 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.

Previous efforts to quantify the effect of climate change on U.S. ecosystems have generally focused on particular areas or industries. An Intergovernmental Panel on Climate Change (IPCC) report last year--which came to similar conclusions as the new report--did include the United States, but it focused more on North America as a whole. Ecologist David Breshears of the University of Arizona, Tucson, says the report is "an important step forward," especially because of its unique emphasis on how abrupt climate changes could upset fragile ecosystems.

The authors, which included federal and academic scientists, found big changes in store for the $200 billion U.S. agriculture industry. IPCC last year forecast a 1.2°C temperature increase for the continental United States over the next 30 years. The authors of the report used that figure to see how crops would respond to such a temperature increase, according to the existing literature. (Warmer weather can help crops, but it can also damage them, for example, by making pollen infertile.) Corn grown in the United States could see as much as a 4% reduction in its yield per acre, the study concluded, whereas rice grown in the South could see a 12% cut. Higher levels of carbon dioxide in the atmosphere could stem the losses, however: Soybean farmers in the Midwest, for example, may see up to a 10% boost in their yields. Moreover, farmers may be able to adapt to many of the changes by altering planting times or the crops they grow, says plant physiologist Jerry Hatfield of the U.S. Department of Agriculture's Agricultural Research Service in Ames, Iowa.

The report cautions, however, that the U.S. climate monitoring system is inadequate for properly measuring regional climate changes, which could make it difficult for scientists to provide meaningful predictions to local businesses or officials. Snow, humidity, and solar radiation measurements are too sparse, for example, and few observations of soil moisture or groundwater stocks exist. Better predictions would require improved climate-measurement tools, more sophisticated climate models that work on regional scales, and a better organized system to integrate all the data, the report concludes.

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