Long-range Weather Muddies the Water

Featured in the December issue of our magazine.
 

By Joli A. Hohenstein

Is feeding a growing population through the uncertainty of ever-changing weather extremes the biggest challenge of our lifetime? Some say yes. And water will play a big role.

Climate experts predict decreased water availability, increased flooding and more frequent and intense droughts in the years to come. Rising temperatures impact snowmelt, river flow, rainfall and groundwater, all of which affect available soil moisture as well as water quality. Fluctuating moisture levels impact crops in myriad ways, from poor root development and reduced nutrient absorption, to increased soil erosion and nutrient runoff to streams and rivers.

While weather has always been dynamic, statistics confirm it has become more unpredictable in recent years, presenting greater challenges to food production. Scientists anticipate the globe will continue trending toward wetter conditions, heavier rain events and rising temperatures.

The Intergovernmental Panel on Climate Change projects 5° to 10° F average global temperature increases are possible by the end of the 21st century. And increasing temperatures can speed up the rate at which crops develop, which can decrease yield and cause other production issues.

“In the short term, I'm not quite as worried about temperature impacts. Illinois has warmed by about 1.5 degrees in the last century,” says Jim Angel, Ph.D., and state climatologist for the Illinois State Water Survey. “However, the warming will get more pronounced as we move forward. So, we will have more issues with heat and pests.”

Also on the rise is precipitation. Illinois’ precipitation levels have been above average for more than 20 years. That affects agriculture in many ways, ensuring adequate soil moisture, but also delaying spring planting. Some estimates say spring rainfall in Illinois could increase by as much as 10 percent in central Illinois and by up to 20 percent in northern Illinois, extending delays.

Extreme precipitation, however, poses a different challenge, notes Angel. These events are defined as the annual number of days with precipitation greater than two inches. The number of these events has been above average since the 1990s. From 2010 to 2014, Illinois experienced two or more extreme events annually – which was a record high for the state.

Angel explains that more frequent, more intense rains make it harder for water to soak into the soil, adding stress to crops. More frequent drought events increase pressures on declining groundwater supplies. As much as 35 percent of Illinois’ arable land is currently drained with tile, which may need to be addressed if climate changes affect soil moisture levels.

“Illinois has become 10 to 15 percent wetter over the last century, and we have seen even sharper increases in the heavy rain events of two inches or more. Even worse, we see a lot of widespread multiday events where we get five to 15 inches over a few days,” Angel says. “And some of those have been in winter when we usually see snow rather than rain. One recent example was in late February of 2018 when four to 10 inches of rain fell in four days, causing widespread flooding in Illinois and especially Missouri.”

Experts say more frequent severe weather events like the 2012 drought and the 1993 Midwest flood are likely, both of which caused billions of dollars in crop and home damage. Increasing flooding has made stormwater management a large and costly issue.

“I think more thought and care will be needed in managing runoff from fields through grass waterways, controlled tile drainage and cover crops,” says Angel. “After the 2012 drought, there was increased interest in irrigation. However, the payoff of that depends on the value of the crop and how easy it is to have access to surface or groundwater supplies.”

Less confidence exists about total rainfall shifts across regions to the west. “We don’t have great certainty in the change in net rainfall across the Great Plains, but the frequency and intensity of drought events has increased. Warming temperatures will increase evapotranspiration rates,” says Meagan Schipanski, Ph.D., assistant professor, Colorado State University Department of Soil and Crop Sciences. “A multi-year drought impacts everyone across the region, but these episodic droughts may impact certain crops more than others – that’s where the challenge lies. Having more diverse crop rotations may help weather some of the shorter-term drought events.”

Angel agrees. “A wetter climate doesn’t mean droughts go away; they may just be shorter and more confined to the growing season. Even in the drought of 2012, the three bad months were May, June and July. The rains began to return in mid-August.”

From 1900 to 2015, Schipanski says there was not a net decrease in rainfall across the Great Plains, but there was more episodic drought and more intense rainfall.

“We’re working with producers now looking back at the 2012 drought,” she says. “What can we learn to be more adaptive and resilient to future droughts? We know where the risks are, but I don’t think we’ve developed cohesive strategies to help communities adapt. We know many best management practices that could help; we just need the incentives that support adoption.”

When thinking about how rural areas can prepare for climate change, Angel recommends looking at ancillary areas that may not be top of mind but impact agriculture just as much. An integrated response and collaborative planning effort may be most successful, involving agriculture, health, municipal and academic entities.

“We need to beef up public health services as well as access to medical care,” he says. “The lasting impression on me from the 1993 flood was not the broken levees or flooded fields. It was the mental and emotional strain of the event. That damage lasted long after levees were fixed.” 

Observed-Number-of-Extreme-Precipitation-Events
The observed number of days with extreme precipitation events (annual number of days with precipitation greater than two inches) for 1900-2014, averaged over five-year periods. The number of extreme precipitation events has been above average since the 1990s.
Observed-and-Projected-Temperature-Change-Illinois
Observed and projected changes (compared to the 1901-1960 average) in near-surface air temperature for Illinois. Since the beginning of the 20th century, temperatures in Illinois have risen approximately 1° F. Temperatures in the 2000s have been higher than any other historical period, with the exception of the early 1930s “Dust Bowl” era.