So Shall You Reap

You might think a little global warming is good for farming. Longer, warmer growing seasons and more carbon dioxide (CO2)—what plant wouldn't love that? The agricultural industry basically takes that stance. But global warming's effects on agriculture would actually be quite complicated—and mostly not for the better.

Based on rationales from "climate change isn't real" to "it will increase crop yields so it's a good thing" to "it will cost us money" most of the country's farming sectors along with their elected officials have staunchly opposed taking action to curb U.S. greenhouse gas emissions. Even after securing several significant concessions—including an exemption from emission caps—congressional members from agricultural states mostly voted against the Waxman-Markey bill (a.k.a. the American Clean Energy and Security Act). But if people who work in agriculture are not worried about the effects of climate change on their livelihood, they should be. "The agricultural industry is really reading the science wrong here," says Nathanael Greene, director of renewable-energy policy at the Natural Resource Defense Council.

It's true that some crops will prosper on a warmer planet, but the key word there is "some." According to a 2007 government report, higher CO2 levels and longer growing seasons will increase yields for fruit growers in the Great Lakes region. But many major American crops, such as sorghum, sugar cane and corn already use CO2 so efficiently that more of it probably won't make much difference to them.

What will make a difference are all the other things we'll have more of as temperatures rise—namely droughts, bugs and big storms. More droughts mean lower crop yields—especially for Southern states. Researchers at the University of Oregon found that in New Mexico alone, reduced stream flow could cost farmers $21 million in crop losses. Meanwhile, melting snow in the Western U.S. will increase water availability in spring but decrease it in summer, forcing farmers to change cropping practices.

As pests adapt their migration patterns to our warmer climate, farmers will have to either use more pesticide (anywhere from 2 to 20 percent more, depending on the crop, according to another government study) or plant hardier crops. Floods and hurricanes increasing in frequency and intensity mean farmers will have to brace themselves for still more crop losses, and the federal crop insurance program (FCIP) will have to get used to writing bigger insurance checks. A single record-breaking Midwestern 1993 flood cost them $2 billion in lost crops.

Farmers on both coasts are already starting to reap some of what the nation's fossil-fuel addiction has sown. Crops in those regions (cranberries in the East and almonds in the West) require a certain number of colder days, or "winter chill" before they break dormancy and begin flowering. Too few cold days disrupts the plants' flowering schedule which in turn affects pollination and hurts yield. A UC Davis study found that winter chill has already declined by 30 percent in California's Central Valley, and almond growers report that yields are down 20 percent from last year. Shorter winters have had a similar effect on cranberry yields in Massachusetts and New Jersey. "It hasn't really hit the breadbasket yet," says Greene. "But it's definitely hitting the country's periphery."