America's Heartland is preparing itself for challenging times. Climate change is predicted to bring increases in summer temperatures, evaporation, and runoff from intense rainfall events, plus a decline in summer precipitation. Together, these conditions could lead to drier soils and more droughts, tough conditions for Iowa farmers.
Currently, Iowa summers are typically hot (average July high is 86°F) and humid with frequent thunderstorms, while winters are very cold (average January high is 29°F) with frequent and persistent snow cover. The average annual precipitation is 34.7 inches, with most of it (>60%) received in spring and summer. Climate scientists generally agree that Iowa's climate will grow considerably warmer and probably drier over this century, especially in summer. Daily maximum temperatures are projected to rise 5 to 14°F in winter and 9 to 22° in summer, the most dramatic warming since the last ice age. Extreme heat will become more common, and the growing season could be three to seven weeks longer.
While total annual precipitation is not expected to change significantly, seasonal precipitation patterns are likely to change, increasing by up to 30% in winter and decreasing 10 to 35% in the summer. When rain does fall in the summer, it will likely come in intense downpours. The frequency of heavy 24-hour rainstorms, which nearly doubled in the 20th century, may double again by 2100. T
Iowa is located in a transition zone between the forested ecosystems to the east and the Great Plains of the central US. The oak savannas and tallgrass prairies of this zone are some of the most threatened plant communities in the Midwest. Historically, they covered large parts of the southeastern portion of the state, but have all but disappeared and are globally endangered ecosystems. Increases in temperature and changes in precipitation patterns due to climate change could further stress oak savannas and tallgrass prairie. As Iowa grows hotter and probably drier, many oak species may be gradually replaced by more drought-tolerant species, such as southern pine or bur oak. Other tree species, such as white pine, balsam fir, and yellow birch, are extremely vulnerable to climate change and may be lost from the state altogether. While increasing atmospheric CO2 would spur forest growth in the short term, higher concentrations of ground-level ozone, more frequent droughts, and a greater risk from insect pests, combined with already existing pressures from invasive species, could damage long-term forest health.
Clemmer, S., and S. Moser. 2004. Climate change in the Hawkeye State: potential impacts on Iowa communities and ecosystems. Union of Concerned Scientists Website (http://bit.ly/8BEV7M). Retrieved 1/6/2010.
Environmental Protection Agency. 1998. Climate change and Iowa. Environmental Protection Agency Publication 236-F-98-007H. Washington, D.C., USA.
The Weather Channel. Average Weather for Des Moines, IA - Temperature and Precipitation. The Weather Channel Website (http://bit.ly/7ak6fw). Retrieved 1/6/2010.