Basic Information

In today's global food market, only three varieties of cereal grains-maize, wheat, and rice-account for about 90% of the world's grain production1 and nearly half of all food calories consumed each year.2 These staple grains feed billions of people daily. Yet to grow productively, they rely on specific environmental conditions. By limiting food-crop biodiversity to just three varieties of grain, the world's food supply is at risk as temperatures warm and extreme weather events, such as heat waves, intense storms, and droughts, threaten to wipe out entire harvests.

Agriculture is highly sensitive to weather events (daily atmospheric conditions, including temperature and precipitation). Even small environmental changes can have serious consequences for crop productivity, especially in areas where plants are already near their temperature thresholds. Yet, while the effects of climate change will almost certainly touch all regions of the world, not everyone will share equally in its hardships.

In seasonally dry, low-latitude areas where most of the world's poor live, small temperature increases can devastate annual crop and pasture yields.3 Research suggests that, India, for example, could experience a 40% decline in agricultural productivity by 2080 as record heat waves scorch the landscape.4 A recent study of South Africa predicts that annual crop revenues could drop as much as 90% by 2100, with small scale farmers most severely affected.5 Developing nations are the most limited in their ability to adapt to rapid changes in climate as well as extreme weather events such as droughts, intense storms, and heat waves.

In parts of North America, however, farmers are hailing climate change as "good news" for crop productivity.6 The Intergovernmental Panel on Climate Change (IPCC) reports that temperature increases and higher levels of atmospheric CO2 will likely increase crop and pasture yields to a moderate degree, at least in the short-term. Weather changes could extend the growing season, and cropland will likely expand northward as the climate warms. Yet, as the CO2 threshold of plants is exceeded and temperatures continue to rise, productivity may begin to slow.7

Despite these mixed assessments of crop impacts, rising temperature could create serious general problems for the world's agricultural sector. One ominous threat of climate change lies in extreme weather events. Drought conditions often lead to wildfires, and intense storms can cause devastating floods. Rising sea levels in coastal areas will make the soil and groundwater more alkaline, further stressing crops that are already struggling.8

Further, as winters and springs become warmer, insects are able to live longer and expand their ranges.9 Pest infestations create stresses on trees and crops, causing direct damage, increasing the susceptibility of plants to disease, and creating conditions that allow invasive species to thrive and indigenous "weeds" to expand. Some studies show that many types of weeds can adapt readily to climate shifts.10 This ability could enhance their ability to out-compete crops for resources like minerals and moisture, diminishing yields.

Along with temperature change, crops are most affected by changes in precipitation. Changing global weather patterns could make some areas wetter, while throwing other areas into drought conditions.11 Farmers could be forced to abandon traditional crops to cultivate heat and drought tolerant varieties. In other areas, farmers are forced to cultivate species able to withstand flood conditions. Scientists are currently working to develop flood resistant rice for Asian producers coping with higher temperatures and flooding conditions.12 Moreover, winter snowpack changes, glacial melt, shifts in stream runoff patterns, and groundwater depletion will have serious consequences for farmers who rely on irrigation.13

Overall, crops depend on "weather" rather than "climate." Scientists agree that climate change can cause extreme daily variations, which could have profound consequences for the world's food supply. The impacts of climate change on food production will depend not only on environmental conditions but on farmers' ability and willingness to utilize new technologies and cultivate different crops to meet the world's changing food demands.14 Small subsistence farmers with the poorest ability to adapt are most vulnerable to the growing impacts of climate change.

  1. Food and Agricultural Organization of the United Nations. (2008). FAO Statistics. Retrieved August 28, 8008 from as cited by New World Encyclopedia. (2009). Cereal Grains. Retrieved July 2, 2009 from

  2. Malin, D. (n.d.). Demands for grains grow at record pace. Retrieved July 2, 2009 from

  3. Easterling, W.E., et al. (2007). Food, fibre and forest products. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Parry, M.L., Canziani, O.F., Palutikof, J.P. van der Linden, P.J., & Hanson, C.E. (Eds.), Cambridge, UK: Cambridge University Press. pp. 273-313.

  4. Cline, W. (2007) Global warming and agriculture: Impact estimates by country. Washington, DC: Center for Global Development & Peter G. Peterson Institute for International Economics.

  5. Easterling, W.E., et al. (2007)

  6. State of Delaware. (n.d.) Climate change Delaware agriculture. Retrieved July 2, 2009 from

  7. Easterling, W.E., et al. (2007)

  8. Peterson, T.C. et al. (2008). Why weather and climate extremes matter in weather and climate extremes in changing climate. Regions of focus: North America, Hawaii, Caribbean, and U.S. Pacific Islands. T.R. Karl, G.A. Meehl, C.D. Miller, S.J. Hassol, A.M. Waple, and W.L. Murray (eds.). A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research: Washington, DC.

  9. Rozenweig, C., Iglesias, A., Yang, X.B., Epstein, P.R., & Chivian, E. (2000). Climate Change and U.S. Agriculture: The Impacts of Warming and Extreme Weather Events on Productivity, Plant Diseases, and Pests. Boston, MA: Center for Health and the Global Environment.

  10. Easterling, W.E., et al. (2007).

  11. Ibid.

  12. Abano, I. (2007). Scientists create flood-resistant rice. Science and Development Network. Retrieved July 2, 2009 from Also see Padma, T.V. (2008). Can crops be climate-proofed? Science and Development Network. Retrieved July 2, 2009 from

  13. Easterling, W.E., et al. (2007).

  14. Easterling, W.E., et al. (2007).