Listen to this articleThe Texas ranch where Gilda Jackson trains and sells horses has been plagued by locusts this year, a problem that only gets worse when it hatches during hot, dry periods. Jackson watched this summer as the insects chewed through a 35-acre pasture in dire need of hay. what they did not destroy the sun burned.
Irrigation may have saved Jackson's hay, but she and her husband scrapped the idea about 10 years ago because of the cost: up to $75,000 for a new well and all the equipment. But now — with a widespread drought and another U.S. heat wave this week that will soak her land about an hour northwest of Dallas for days in temperatures above 100 degrees — Jackson said she's “rethinking it.”
Many more U.S. farmers and ranchers may be forced to do the same in the coming decades, according to recent research on the expected effects of rising heat and more frequent extreme weather events associated with climate change.
That's if they even can. Some parts of the US are already struggling with groundwater depletion, including California, Arizona, Nebraska and other parts of the central plains.
“It's no surprise that in the future, when it's hotter and there's more demand for water, people will use more water,” said Jonathan Winter, associate professor of geography at Dartmouth College and author of a new study on the future. Costs and benefits of US irrigation in Land and Environment Communications.
Winter and his team used a computer model to examine how heat and drought could affect crop production through the middle and end of this century, given multiple scenarios for greenhouse gas emissions. In places like California and Texas where “everybody's throwing their straws in the glass” of groundwater, as Winter put it, current irrigation levels won't be sustainable in the long term because there isn't enough water.
But irrigation use can be increased where groundwater supply is not currently a problem.
In much of the Midwest, including the corn- and soybean-rich states of Iowa, Illinois, Indiana and the Dakotas, farmers may see a benefit over the next 50 years from installing irrigation infrastructure. This is a costly investment, and whether it pays off may depend on people's ability to limit the worst effects of climate change. A worst-case scenario would involve one generation investing in expensive irrigation equipment, only for the next to fail to keep crops alive due to extreme heat and weather.
There are many methods of irrigation for row crops, but the most common is rotary irrigation – long strips of pipe mounted on wheels that are pulled in a circle around a water source to sprinkle water over a field. The equipment can easily cost hundreds of thousands of dollars, plus the cost of drilling a new well if needed, along with the electricity to pump the water.
But if the system increases yields and provides a return of $50 per acre or more, it can pay off well for a farmer, said Brady Brewer, associate professor of agricultural economics at Purdue University.
While scientists are certain about the warming effects of greenhouse gas emissions, precipitation is harder to eliminate, especially in the Midwest, said Dave Gochis, a senior scientist at the National Center for Atmospheric Research who was not involved in Winter's study.
Climate change is causing more extreme weather, which means both an increased risk of flash droughts—rapid, intense periods of short-term heat and dry weather—and more heavy rainfall and flooding as precipitation increases with more water in the atmosphere.
“That means we have to be more nimble and flexible in how we manage water resources,” Gochis said.
Brewer has yet to see much increased interest in irrigation from Midwest farmers. So far, excess water has been the biggest problem in many places, but if yields start to suffer in the coming years due to worsening heat and drought, “that's when farmers will invest,” he said.
Farmers who don't opt for irrigation, for now, can get by by planning ahead.
They could choose different crops with different water needs from season to season or be compensated for fallow during periods of water stress. Or they might use tools like the one developed by North Carolina State researchers Sankar Arumugam, professor, and Hemant Kumar, Ph.D. candidate.
They recently helped create a computer modeling tool, described in the journal Water Resources Research, that they hope will help farmers and water managers use a combination of seasonal forecasts and other data to find a sweet spot for balancing water revenue. crops and water use.
In the southeast, where they focused their work and where water resources are abundant, “it's more of a precautionary strategy” for people who already have irrigation equipment, Arumugam said, “so that we don't overexploit the resources that are there. ”
Irrigation, used responsibly, can be part of climate change adaptation, but “it's a moving target,” Winter said.
He called for supporting farmers who have to make difficult decisions as they adapt to climate change – for example, by training them to grow less water-intensive crops or giving them low-cost loans to improve irrigation efficiency.
However, he also urged action to limit the worst effects of climate change. Farmers need resources to make adjustments, but especially in the West “there's only so much water,” he said.
Upmanu Lall, director of the Columbia Water Center, said climate change isn't the only thing driving farmers' decisions. Lal, who was not involved in Winter's work, said crop insurance and government subsidies can push farming methods in one direction or another.
Brewer, the Purdue professor, agreed.
“What we're seeing is because we have crop insurance that reduces farmers' risk, that's probably what's driving some of those farmers to plant soybeans or corn” instead of more drought-tolerant crops like wheat or sorghum in places like the western Plains, Brewer said.
He added that research shows if farmers have crop insurance and feel safer planting crops that use more water, this “may lead to higher irrigation uptake as well.”
