Thursday, October 14, 2010

A look ahead at the climate for agriculture in the Midwest

A look ahead at the climate for agriculture in the Midwest

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Coming up in early November, the Environmental Change Institute at the U of I will hosts its annual summit, a one-day colloquium on the topic, “Climate Change: Agricultural Solutions, Adaptation and Mitigation.” Next week I’ll provide a sampling of what attendees at that summit can look forward to. (Of course, if you're reading the electronic version of this segment, you can easily look ahead for yourself: But this week, I want to set the stage for the summit by providing a quick look at the climate picture for agriculture in the Midwest in the century to come.

This picture is drawn from a recent (soon to be published) report co-written by U of I professor of atmospheric sciences Don Wuebbles (who is a sharer in the 2007 Nobel Peace Prize for his work with the Intergovernmental Panel on Climate Change), his colleague at Texas Tech, Katharine Hayhoe, and U of I student, Ben Garrett.

The report focuses on impacts from climate change that will require farmers to change how they operate, impacts that will vary according to whether or not people act effectively to reduce greenhouse gas emissions. The higher emissions scenario used to make projections in the report assumes a combination of fossil fuel use and population change that results in an atmosphere with greenhouse gases at more than triple pre-industrial levels. The lower emissions scenario assumes a shift away from fossil fuels, with atmospheric greenhouse gas levels at the end of the century only double those of preindustrial times.

Under either scenario, summers in the Midwest are projected to be hotter. Over the next thirty years, somewhere between 50 and 70 percent of summers will be characterized by median temperatures that equal or exceed the hottest summer of the historical reference period of 1961-1990. By midcentury, according to the report, nearly all summers will be hotter than that, even under the lower emissions scenario.

Heat waves, which can negatively affect crop development and stress livestock, are also projected to increase in number and intensity. In this case, the difference between high emissions scenario and low emissions scenario is pronounced. Under the high emissions scenario, for example, even Wisconsin and Minnesota would be expected to experience weeklong stretches of 95-degree days every other year by the end of the century. Under the low emissions scenario, such weeks would more likely occur in only one year out of four.

The report also projects warmer winters for the Midwest, and anticipates how that will affect agriculture in two ways. It projects a decline in “accumulated chilling hours,” which results in the northward migration of corn pests that are limited by periods of pronounced cold. It also projects a decrease in productivity for fruit crops that depend on a prolonged winter chilling period to flower, including things like apples, grapes and blueberries.

The report points out that warmer winters will also mean the continued northward migration of plant hardiness zones, which are defined by the coldest temperatures of the year. Already plants that used to be typical of southern Illinois can be grown in the Chicago area and much of Michigan. By the end of the century, the report projects, conditions once associated with the Southeast are likely to take hold in much of the Midwest.

Warmer conditions in spring and fall are also anticipated to extend the growing season in the Midwest. The degree to which that is a benefit will depend largely on whether precipitation patterns allow farmers to get into the fields earlier in the spring.

Are you interested to know more about the implications of climate change for agriculture? Check back next week for a preview of the Environmental Change Institute’s annual summit.