Global warming is causing fluctuations in crop yields, prices and farm income, a new study says.

X.B. Yang, associate professor of plant pathology at Iowa State; Paul Epstein, ecologist at Harvard University Center for Health and Global Environment; and Cynthia Rosenzweig, of Columbia University Earth Center; conducted research for a study that was presented at a congressional briefing on May 25 at Capital Hill in Washington, D.C.

“It is well known that global temperatures have increased drastically since the early 1970s,” Yang said. “The increase has arguably been attributed to human activities.”

Epstein agreed that humans are in part to blame for global warming.

“Today, the activities of one species, humans, are reducing the diversity of all others and transforming the global environment,” Epstein said.

“The consequences for agricultural pests and crop yields may be significant.”

The study looked at data over a course of many years.

“We examined data from 1950 to the present and found drastically increased fluctuation of crop yields since the 1970s,” Yang said.

The warmer temperatures have created numerous problems, according to the study, and people in agriculture are seeing more widespread crop diseases.

“Plant parasites are very sensitive to environmental changes,” Yang said. “I have observed numerous plant diseases that expanded their distribution ranges since the 1970s.”

“Some Southern diseases are becoming production problems in the north region.”

Also, new diseases are causing grief for farmers, Yang said.

“Two recent examples are soybean sudden death syndrome and the bean pod mottle virus of soybeans,” Yang said.

“The two diseases are considered new threats to the soybean industry.”

Yang said if the temperatures were to continue increasing, a variety of changes would happen.

“A change in the climate may result in a shift of the production center,” Yang said. “For example, the Corn Belt may move northwestward.”

Growers may have to deal with pests and diseases that are now only in the South, Yang said, which could increase production costs and pesticide-related environmental concerns.

But Yang stressed that research is being conducted across the country to correct this problem.

“Scientists are working on the solutions,” Yang said. “One process under study is carbon sequestration.”