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Climate change 101

Think climate change is a massive Al Gore-led conspiracy designed to limit how you farm?

Maybe. There's a powerful case to be made, though, that man-made climate change is occurring. Worldwide, over 100 scientific societies say man-made climate change is happening. This includes 97% to 98% of scientists actively publishing climate research in scientific journals.

“There is a tsunami of scientific agreement that man-made climate change is occurring,” says Paul Vincelli, University of Kentucky Extension plant pathologist.

Farmers and farm groups generally are leery of man-made climate-change reports, due to fear of any legislation that may restrict fuel use or the way they farm.

“For now, cap and trade is dead politically,” says Mike Boehlje, Purdue University agricultural economist. “But the fundamental issue of concerns over global warming has not gone away. Our perspective is it may be in remission for a while, due to issues like balancing the budget.”

Regardless of climate-change politics, now is a good time to ready your farm in case the studies are true.

The good news

Bear in mind that if man-made climate change is occurring, you'll see it over a period of time. After all, it took since the mid-1800s for atmospheric carbon dioxide levels to rise from 280 parts per million (ppm) to the current 392 ppm. In some ways, this increase is good news.

“When you increase carbon dioxide, crops grow better,” says Nick Harmon, director of sustainability for Bayer CropScience. “Crops, in general, will have a reduced number of stomata. Stomata are the mode of gas exchange in plants. They are also the way plants lose water.”

Rising temperatures provide some good news for those of you in Northern areas. Longer growing seasons will generally occur. For example, farmers in Iceland have been able to grow barley for the first time in recent years, says Harmon.

This will help farmers in the northern Plains grow more winter wheat. Traditionally, farmers in states like Minnesota and North Dakota have been caught in a wheat tug-of-war. Historically, winters have been too brutal for winter wheat to survive winters like those in North Dakota. Meanwhile, spring wheat risked cooking in hot summers during kernel formation.

Milder winter temperatures will expand winter wheat production that's already occurring in these areas, notes Harmon.

The bad news

Unfortunately, diseases and insects also thrive under higher temperatures and carbon dioxide levels. Forest insects are already shifting northward in the United States.

“The western pine beetle is moving northward in California, and bark beetles are moving into Alaska,” says Harmon. “These insects are hard to manage.”

This scenario will likely apply to agricultural insects. Warmer temperatures will lead to increased fecundity (egg-laying),” says Harmon. “Insects better survive winter and have earlier flight times, which enable more than one generation per year to survive.”

In 2008, Purdue University scientists examined survival temperature thresholds of corn insects with a detailed U.S. climate-change model.

Milder winters spurred by climate change could lead to corn earworm, European corn borer, and northern and western corn rootworm expanding their range, the Purdue scientists found.

Particularly disconcerting is the outlook for corn earworm.

“It is resistant to several existing pesticides, and adult moths are capable of being transported long distances in the jet stream to infest new crops,” says Christian Krupke, a Purdue University Extension entomologist.

Vincelli says the diseases that migrate from Southern regions each year may be able to migrate earlier in the year and farther north. In some cases, insects and disease migration go hand in hand. Flea beetle is an insect that transmits Stewart's wilt in corn. Increased flea beetle survival from higher temperatures in winter could boost Stewart's wilt infections.

Since weeds love high carbon dioxide levels as do crops, you'll have to contend with more weed problems. One harbinger of weeds to come includes the proliferation of yellow star thistle.

A 2011 Purdue study found this pasture weed grew six times its normal size when exposed to increased carbon dioxide, precipitation, nitrogen, and temperature. Meanwhile, all other grassland species remained relatively unchanged.

Climate change will also mean an increase in abiotic stressors, like wet conditions at spring planting.

Keith Cherkauer, an associate professor of agricultural and biological engineering at Purdue, ran simulation models that show Indiana, Illinois, Wisconsin, and Michigan could see as much as 28% more precipitation by the year 2070, with much of that coming in winter and spring.

What to do

If these changes occur, solutions exist. “In agriculture, have lots of tools in the toolbox to deal with climate change,” says Harmon.

Seed is a good place to start. “We are improving crops that are tolerant to heat, drought, or salt, and that create more efficient uptake of nutrients,” says Lykele van der Broek, global chief operating officer for Bayer CropScience.

Most corn and soybean farmers already use Roundup Ready crops. That's a climate-change plus, since those crops conserve fuel use and help soils sequester carbon, says David Gustafson, a senior science fellow and the environmental and ag policy modeling lead for Monsanto.

Ditto for insect-resistant crops, which decrease chemical use and the greenhouse gas emissions that result during manufacturing and field application.

A trait to improve nitrogen use by crops will slice emissions of nitrous oxide. This gas has about 300 times more impact per unit weight in global-warming potential than carbon dioxide, says Gustafson.

Crops that can withstand short-term flooded conditions are also on the way, although it's a ways into the future.

“It's quite difficult to identify the genes responsible to improve tolerance against abiotic stress,” says van der Broek. “To combine them with high-yielding varieties is quite a challenge. We'll get there, but it will take time.”

Since milder temperatures likely will spur more pests, you'll have to keep an eye out for weeds, insects, and diseases. If they migrate though, products that control them in current areas will work elsewhere, says van der Broek.

Uncertainty still exists about the extent of climate change.

“It's a complex web,” says Harmon. “We don't know exactly what it will look like, but modeling tells us that pests will be expanding their range.”

Learn more

University of Kentucky www.ca.uky.edu/agc/pubs/id/id191/id191.pdf

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