Global climate change is projected to have significant regional impacts on agriculture and the production of food and fiber for human use and consumption. Greenhouse warming is one of the complex factors that will shape global food production in the coming century, as the world faces the challenge of feeding a rapidly growing population, which is projected to double from 5.7 billion to over 10 billion by the middle of the next century. Through changes in temperature, water regimes, and carbon dioxide (CO2) levels, global climate change will directly affect crops, soils, pests, and livestock. Both producers and consumers, within the United States and abroad, will experience the impacts of these changes. Farmers can respond to many of the direct effects of climate change by adjusting their practices, while food-buyers may find variations in the quantity, quality, and prices of produce in their local markets. The challenge for the world agricultural enterprise is not only to feed the growing population in the face of changing climate conditions, but to do so while preserving the rich resources of land and water on which we and future generations depend.

The Intergovernmental Panel on Climate Change (IPCC) Second Assessment Report concluded that global agricultural production appears to be sustainable in the face of climate change as predicted by global climate models (GCMs) for doubled-CO2 equilibrium scenarios. Current research suggests that the transient nature of climate change, potential alterations in climate extremes, and differential regional responses may temper positive outcomes. These processes and their potential impacts on food security for vulnerable groups will be examined more fully in upcoming IPCC Assessments.

The Great Plains region produces nearly one quarter of the nation's agricultural crops and livestock. Agricultural production and water resources in the region are known to respond nonlinearly to the frequent extremes in temperature and precipitation in the current climate. Small changes in already marginal climate conditions for many agricultural systems in the Great Plains may produce disproportionately large impacts. Large climate changes could severely diminish the comparative advantage of farmers and ranchers in the region and further stress irrigation water supplies.

Factors that are likely to influence the comparative advantage of Great Plains farmers over the next few decades include, for example, the ability of the agricultural research establishment to promote technical progress that increases farm productivity and reduces environmental damages, the relative growth of scientifically based agriculture in developing countries (e.g., Argentina, Brazil, Vietnam) that increasingly compete with Great Plains farmers, and the occurrence of extreme climate variations in the Great Plains that either stress or benefit farmers there relative to their competitors.

A plausible future of Great Plains agriculture 30-40 years hence, absent climate change, will be described in which farmers are two to two and a half times as productive as they are today due to anticipated technological advances in agronomy and animal husbandry. However, real prices for agricultural outputs are likely to be declining as farmers worldwide become more productive and costs of production fall. Previous studies using the hot, dry ÒDust BowlÓ years of the 1930s as an analog of climate change found that, were such conditions to recur today, yields of major Great Plains dryland crops such as corn could decrease by 15-20% if farmers did nothing to adapt. Water use for irrigation would increase by a similar amount if the water were available. Simple adaptations such as altering planting dates and changing crop varieties could make up for much of the yield loss, but not all of it.

Studies indicate that the comparative advantage of Great Plains agriculture in crops currently grown is not likely to be as great in the future as it is currently, even if the climate remains unchanged. Climate change appears likely to stress farming conditions even more, although efforts by farmers to adapt to climate change are likely to offset some of the climate-related damages. Unpriced environmental costs of adapting to climate changes such as the implied loss of water quality and quantity, are likely to make adaptation appear less costly than could actually be the case. Based on these many considerations, it is not likely that Great Plains farmers will maintain the comparative advantage they once enjoyed, whether the climate changes or not. Climate change, if the change is for the worse, is likely to further erode the position of Great Plains farmers, even if efforts to adapt offset some of the crop losses.

Dr. Cynthia Rosenzweig is a research scientist at the NASA Goddard Institute for Space Studies (GISS) and Columbia University. She currently leads the Climate Impacts Research Group at GISS, with which she has been affiliated since 1984. The mission of the group is to investigate the interactions of climate (including both variability and change) on systems and sectors important to human well-being. Dr. Rosenzweig recently led an interdisciplinary study for the U.S. Environmental Protection Agency on climate change, agriculture, and food security, with participating scientists in 25 countries. She is also the lead technical expert on the Agricultural Vulnerability and Adaptation Assessment of the U.S. Country Studies Program and a principal lead author of the Agriculture Chapter in the IPCC Working Group II Second Assessment Report.

Dr. Rosenzweig received her B.S. degree in Agricultural Sciences from Cook College in 1980; her M.S. degree in Soils and Crops from Rutgers University in 1983; and her Ph.D. in Plant and Soil Sciences from the University of Massachusetts in 1991. Her research focuses on the potential impacts of environmental change, including increasing carbon dioxide and global warming, on agricultural production at regional, national, and global scales.

Dr. William E. Easterling is an associate professor of agricultural meteorology in the Institute of Agriculture and Natural Resources of the University of Nebraska-Lincoln. He is the director of the Great Plains Regional Center of the National Institute for Global Environmental Change (NIGEC) and the acting director of NIGEC. His doctorate is in geography from the University of North Carolina at Chapel Hill. Prior to joining the University of Nebraska-Lincoln he was a fellow in the Climate Resources Program of Resources for the Future. Dr. Easterling's research concerns the interactions of human activities with their climatic and biotic environment. His research focuses on the possible effects of climate changes from greenhouse warming on agroecosystem productivity and adaptation in marginal environments such as the North American Great Plains. He participated in a large interdisciplinary study funded by DOE to examine the implications of climate change for the resource base and economy of the Missouri-Iowa-Nebraska-Kansas (MINK) region. With support from NSF, Dr. Easterling is currently examining the combined effects of climate and land use change on the terrestrial carbon cycle of the Great Plains. With support from NASA and EPA, he is participating in a study to develop regional estimates of the effects of El Nino/Southern Oscillation-forced climate variability on southeastern U.S. agriculture and economy. He has published widely on the above topics and serves on numerous scientific committees.