Climate change stressing soil: more efforts needed

May 9, 2014

Soil conservation practices will become more critical as weather volatility increases with higher temperatures and rising atmospheric carbon-dioxide levels, said one of the lead authors of the agriculture chapter in the National Climate Assessment released last Tuesday.

The National Climate Assessment, a report mandated by Congress, examines the way climate change will affect different industries and regions of the country, as well as adaptation strategies to cope with the effects.

As the food system becomes increasingly globalized, more extreme weather will pressure food security in the coming decades. Commodity prices will become more volatile as food production is disrupted.

Climate change will affect agriculture, though farmers in some parts of the U.S. could see benefits from longer growing seasons while others will suffer. In the Midwest, for instance, higher levels of carbon dioxide in the atmosphere could translate into longer growing seasons that will boost yields for some crops over the next 15-20 years. Production gains would continue despite more frequent extreme weather events such as heat waves, droughts and floods.

One of the major takeaways from the report is that agriculture can adapt, but protecting land and water resources will become more critical, said Jerry Hatfield, a USDA soil scientist in Ames, IA, and one of the lead authors of the chapter about agriculture. Extreme variability in precipitation will increase soil erosion through either intense rainfalls or droughts and high winds. These challenges will require more innovative conservation practices in the future.

“We’re seeing shifts in seasonality and more extreme events on precipitation leading to greater erosion,” Hatfield said. “That is one of the major things to be concerned about in the short-term. Protecting our soil resources, in my opinion, is one of the biggest things we need to be doing.”

While the Midwest could see stronger short-term production, that’s not the case for the Great Plains. The report states the Great Plains won’t be able to keep up with growing water demands. Climate change is already affecting rainfall in the region.

Too little rain is falling to replace the water needed by people, plants and animals. “As these trends continue, they will require new agriculture and livestock management practices.”

The benefits of longer growing seasons are being tempered by wetter springs in the upper Midwest. Farmers are crunched for time and facing delays getting their crops in. Moreover, the probabilities of late or early frost have not changed and can negate the length of the growing season. “I think the thing the producers need to be aware of is to expect a lot of volatility in the weather from year to year because we are going to see wider extremes,” Hatfield said. “The climate projections are taking us toward wetter springs, hotter and drier summers.”

Hatfield points to 2012 in Michigan when perennial crops such as cherry trees saw early warm temperatures in spring 2012 only to be hit with a late freeze that killed the crop. The same problems hold true for commodity crops.

“I think producers can weather these events—to use a bad pun—but they are going to have to be aware that the conditions in which they are producing these crops are going to be different than they were in the past.”

We’re going to have to look very hard at conservation practices to protect the soil from erosion, Hatfield said. That means leaving higher levels of residue on the ground and changing crop rotations to add cover crops to both build organic matter and increase water-holding capacity in the soil.

While a lot of researchers study how crops respond to higher temperatures, water needs and carbon dioxide levels, fewer researchers consider how those changes affect the land that feeds the crop, Hatfield said. Yet, intense rainfalls in the Midwest lead to higher levels of soil runoff while high winds and heat on the Plains are picking up the soil and sparking more frequent and intense dust storms.

“I’m not sure a lot of people thought about how fragile our soil system is and what the climate is doing to it. We tend to look at crop productivity and all that variation of yield, but the soil piece relative to the climate discussion often goes by the wayside. It’s not part of the conversation. We’ve had these more extreme events so we are picking up a lot of wind. If we don’t have cover, then we are picking up a lot of wind erosion too.”

The wheat belt will likely push north because of growing stresses on the crop. In states such as Texas, farmers may adapt by planting shorter-season corn varieties to reduce some of the stress that comes with higher temperatures in August—assuming the farmer has access to water.

“The piece of the higher temperatures that people forget is what it does for increased water use for the crop,” Hatfield said. “You have increased water use by the crop that ends up with a lot of water stress on the soil very quickly.”

Matt Russell, a farmer from Lacona, IA, said last week on a call organized by the Natural Resources Defense Council that extreme weather in Iowa has become a growing concern over the last decade. He noted that last year a foot of snow fell in May across parts of Iowa that led to 800,000 acres of prevented-planting claims. More farmers have installed tiling systems to help drain water from the ground so they can more easily plant their crops.

“There may be some farmers out there who are still denying climate change is happening, but trust me, none of us are ignoring it,” Russell said.

Lewis Ziska, an Agricultural Research Service plant physiologist, has studied how weeds, diseases and insects will become bigger challenges in the future because invasive species thrive in warmer conditions and with higher carbon dioxide levels. Farmers recognize they are seeing increasing challenges trying to grow crops. One problem in talking to farmers about these biological reactions is the political divide over climate change, Ziska said on the NRDC call.

“Is it climate change? Oh no, it’s not climate change. That’s Al Gore. It doesn’t have anything to do with what we’re seeing. So often this issue of politics as opposed to science comes into play when you want to call something one thing that becomes a loaded term,” Ziska said. — Chris Clayton, DTN