DAVENPORT - A report released Thursday by Environment Iowa showed that Iowa corn growers lose $259 million a year because of global warming.

The annual loss to Iowa farmers tops all 50 states. Illinois is a close second, with a $243 million annual loss, according to the report. The report says that agriculture and the renewable-energy industry can help slow the problem.

The loss is based on lower yields caused by a 2-degree increase in average temperature, said Julian Boggs, Environment Iowa field associate. Francis Thicke, a Fairfield farmer, said studies have shown warming has dropped production by 13 bushels per acre.

Boggs and Thicke were joined at a news conference in the Davenport Police Department's community room by Jerry Neff, president of the Iowa chapter of the Sierra Club, and Mike Carberry of the Iowa Physicians for Social Responsibility.

Iowa's per-acre yield for field corn in 2006 was 166 bushels, while last year's yield was 171 bushels, according to the U.S. Department of Agriculture's National Agricultural Statistics Service. That is up from the 2001 yield of 146 bushels per acre but down from 181 bushels per acre reported in 2004.

Illinois' bushel-per-acre yield in 2008 was 179, down from a high of 180 bushels per acre in 2004. Since 2001, the average yield has been as low as 135 bushels per acre, in 2002.

The report doesn't take into account extreme weather events, such as tornadoes or flooding, or the expanded range of pests, weeds and crop disease.

It does note that global warming increases the growing season and carbon dioxide levels that encourage plant growth.

Although soybeans also are large cash crops in Iowa and Illinois, the researchers chose to focus on global warming's effect on corn.

"It is the canary in the coal mine in the agricultural spectrum of global warming's impact," Boggs said.

Boggs' group would like to see more clean energy promoted, including wind and solar power, through clean-energy legislation that President Barack Obama has requested.

"These solutions will benefit the economy," Boggs said.

The groups represented at the news conference want U.S. Rep. Bruce Braley, D-Iowa, to support clean-energy and global-warming legislation. Braley serves on the House Commerce and Energy Committee. A draft piece of legislation has been introduced in the committee.

The congressman is supportive of renewable energy but wants to see firm language and numbers before backing the bill, spokesman Jeff Giertz said.

"The chances to slow global warming are good for the local, regional, national and world economies," said Carberry.

Neff said Iowa and some of the Quad Cities - Rock Island and Davenport in particular - are doing a good job at being environmentally friendly.

Contact Kurt Allemeier at kallemeier@qctimes.com.