The Midwest's cold winters play an important role for farmers: They prevent devastating crop pests such as corn earworms and corn borers from becoming established in their fields. Corn earworm pupae, for example, can't survive more than about five days at temperatures below 14 degrees Fahrenheit.
As global warming continues, however, the range of crop pests and their ability to survive the winter increases.
"Increases in temperatures, even summer temperatures, generally benefit these pests. An effectively longer season, or more days exceeding their minimum temperature range, provides them with additional time to feed, mate and reproduce," said Purdue University entomologist Christian Krupke, who studies the impact of climate change on crops pests.
The corn earworm is just one clear threat. It's already established in the South and has resistance to many of the current pesticides, making it tough to manage.
Scientists expect climate change will similarly impact many types of crop production across the U.S. in the next several decades as deadly crop pests and fungi flourish in the warmer and, in some areas, wetter weather.
As warming increases, three issues affect U.S. crops in terms of pests:
*survival thresholds rise, leading to overwintering and more generations every year;
*ranges push northward, leading to new kinds of pests in areas that haven't formerly had to deal with them; and
*increasing use of pesticides to offset the first two effects, leading to increasing tolerance of existing pesticides, will further exacerbate the pest problem.
A U.S. Global Change Research Program report (which was withheld by the Bush administration) projected that climate change would cause an increased use of pesticides over the next 80 years on corn by 10 to 20 percent, on potatoes by 5 to 15 percent, on soybeans by 2 to 5 percent, and on wheat by an unknown quantity.
Another potentially deadly impact on wheat was discovered in Uganda in 1999: the wheat stem rust Ug99. It is described as a "time bomb" for world wheat production and has already spread to Iran. Scientists are working on hybrid strains of wheat that show resistance to Ug99.
If the fungus makes its way around the globe, it represents a significant threat to global food security, says Rick Ward, a wheat geneticists at Cornell University. Wheat is the staple food of billions, matched only by rice in Asia.
For U.S. food in general, the impacts of climate change and hardier pests might be as straightforward as higher food prices, as farmers resort to more insecticides to keep crops from being ravaged and spend more in labor costs for "spotters" to identify pests in their fields. Or the effects might become as complicated and devastating as the food shortages currently being experienced in some third world countries. It all depends on how timely and comprehensive U.S. policy is in dealing with greenhouse gas emissions like carbon dioxide.
As David Wolfe, professor of plant ecology in Cornell University's Department of Horticulture (and a leading authority on the effects of climate change and rising atmospheric carbon dioxide on plants, soils and ecosystems) asked in his recent op ed, how far are we willing to let it go?
His answer was more hopeful than one might expect:
"I've been doing climate change research for 20 years, and I am encouraged that we have begun debating what to do instead of simply debating whether it is real or not. We seemed to be stagnating for a long time. Now, a lot of valid discussion and policy options are being presented. But we certainly have a lot more to do."
That "a lot more" includes not only assuring American food security, but providing the sort of variety Americans have grown accustomed to – a variety that is remarkable both spatially and historically.
Consider this: Many Americans born after 1980 can't imagine a time when fresh tomatoes, avocados, oranges, melons and even pineapples weren't readily available on supermarket shelves, not merely in summer but in the dead of winter.
In fact, this modern availability is a recent phenomenon, arriving after WWII and driven by technological advancements in farming, harvesting and shipping food that allowed farmers from Florida to California's Central Valley to ship produce to eaters in the Upper Midwest.
It hasn't always been this way. In 1950, a pineapple in winter was a rare event. In the 1940's, an orange at Christmastime was even rarer, and if you got one in your stocking you knew you had impressed someone with your exemplary behavior.
As crop pests drive food production downward, and food costs upward, this new paradigm may fail and reliance on locally grown foods return as a way of life. We won't starve, Wolfe says, confident in the American farmer's ability to cope with climate change, but things may be very different.
Predicting how different, Wolfe says, would be impossible.
"At the very least, we can say that farmers growing today are first generation in the history of human race to not be able to use historical data for where and when they grow crops. That is, for thousands of years we've had fairly stable climate, but the pace of change we're seeing now, and may see for the next hundred years, is unprecedented. That's a big challenge."
Still, Wolfe remains convinced that science can keep ahead of climate change.
"In the Northeast and Midwest, we are facing increasing insect pressure the likes of which farmers have never seen before. The most important element, going forward, is that these farmers have reliable information."
That is where Wolfe, and Art DeGaetano, director of the Northeast Regional Climate Center (NRCC, Dept. of Earth and Atmospheric Sciences) at Cornell University, come in. Wolfe works on the plant science/climate change side, while DeGaetano, in his role for NOAA (which funds the NRCC), focuses on gathering climate data, interpreting it, and feeding it into the public domain to allow timely, effective adaptation to climate change scenarios.
Wolfe, whose focus on the effects of climate change on natural and managed ecosystems has increased since the early 1990's, has worked with both the Union of Concerned Scientists on a Northeast regional climate change impacts assessment and the U.S. government in determining carbon emissions policies. He is equally confident of the American farmer's adaptive capacity when it comes to climate change.
"American farmers are smart, and they're used to scrambling to meet changes. The problem with climate change is, it doesn't always send a clear signal when to begin adapting. For example, it may take a series of low-yield years and financial losses for farmers to switch from apples, for example, to fruits more adapted to a warmer climate."
Unfortunately, as DeGaetano notes:
"Such changes are not incremental and constant, but surge forward in some years, and then are knocked back by an unusually cold winter, or a warmer than normal summer, for example."
Coping will undoubtedly include more pesticides, a factor which itself presents a number of environmental and economic problems.
Another climate change factor is increasingly warmer wintertime temperatures, which have the dual effect of allowing pests to produce more offspring and preventing fruit and nut trees from blooming for lack of a sufficient "chill factor" (which triggers spring flowering).
Crops can be genetically modified to withstand harsher conditions, but Wolfe stresses a need for regulation:
"My take is that GMO, like most aspects of agricultural technology, needs to be regulated to be sure we're not releasing things into the environment that will have negative effects. That being said, these new technologies might produce varieties that help farmers cope with climate change, providing seeds are made available, and affordable, to all."
"GMOs are to agriculture what diversifying is to a retirement portfolio. They may help us adapt to the wild swings in rainfall, drought, and temperature."
One overriding concern Wolfe noted is the capacity of America's small family farms to survive the costs associated with climate change.
"Unlike factory farms, small farmers may not have the capital to make needed shifts in time, and some may be forced out of business unless there is a policy put in place to help them transition to the new climate."
This may be the worst scenario of all, as pollutive but well-financed mega-growers gobble up smaller landholdings, producing enough food to feed America but simultaneously causing deterioration in the quality and safety of that food.
Proof that climate change is causing a dramatic shift northward – not only for crops pests but for plant and animal species – abounds, but nothing is more poignant, or more telling, than the recent sighting of a brown-backed solitaire in Southern Arizona. Prior to July 25, the small bird had never been seen north of the Mexican border.
(Photo: USDA/Scott Bauer)