She authored the US Department of Agriculture (USDA) report: Climate Change, Water Scarcity and Adaption in the US Fieldcrop Sector, which predicts the potential influence of climate change on feed crops grown in different parts of the US and on some adaptive techniques, like irrigation, used to mitigate those effects.
“Our system of agricultural production is not static; farmers will adapt by altering what they grow and how they grow it,” she said during a presentation on the report.
The report covered nine potential climate projections and looked at possible outcomes in 2020, 2040, 2060 and 2080 for several different parts of the country.
Crop yield and prices
Crop yields for most feed crops including corn, sorghum, soybeans and silage are expected to fall throughout the century, and yields for all feed crops are expected to drop by 2020, according to the publication.
Corn production could decrease by about 8% by 2020 and 16.2% by 2080, it claimed. Those estimates are based on national productions from all the different pathways assessed.
Similarly, soy bean output might see a reduction of 8.1% in 2020 and 14.3% by 2080, noted the report. It forecast that sorghum yield could drop by 15.1% in 2020 and 17% by 2080.
However, not all plants would react the same. Barley, hay and wheat are expected to have increased output in the long term.
By 2080, barley could improve by about 1%, hay production by 4.2% and wheat by 11.6%, found the report.
As crop yields drop, prices are expected to increase, they said. Across the different scenarios, average price increase would jump to about 10.4% by 2080.
One adaption process the USDA group involved in the report examined was irrigation and how crops would fair in an irrigated or dry land, non-irrigated, production system, said Marshall.
Yields for most feed crops fell regardless of if irrigation was used or not, she said. However, use of irrigation also was predicted to dwindle for parts of the country over time.
About 46.8m acres of crop land are expected to be irrigated by 2020, forecast the report. But, by 2080, that amount is predicted to fall to roughly 45m acres, depending on climate scenario.
“After midcentury, declines in irrigated acreage are generally greatest for corn and hay,” predicted the USDA team. “Cotton and soybeans also lose significant acreage under some climate projections. Acreage in irrigated hay—with generally lower returns to irrigation and high water consumptive requirements—is particularly sensitive to increasing constraints on water supply; irrigated hay generally declines across the Mountain region, for instance, despite increased yields in that region under several climate projections.”
Use of irrigation may change by region. The Mountain and Pacific regions could see movement from irrigated to dryland production, and the southern plains also are expected to have less irrigated acres.
And the Corn Belt is predicted to lose both irrigated and dry land production, forecast the publication.
“Acreage impacts in the Northern Plains are mixed for both dryland and irrigated production, with some scenarios showing significant increases and others showing significant decreases,” said researchers. “The Delta region generally experiences a contraction in both irrigated and dryland acreage, suggesting a loss of comparative advantage under climate change.”
Changes to precipitation and heat stress influencing plant growth may mean it ceases to be economical to continue irrigating, found the USDA team.
“Shifts in the physical availability of surface and groundwater supplies may alter water costs for agricultural uses, although costs of purchased surface water and pumped groundwater may not necessarily reflect the scarcity value of water," noted the report. “Increasing competition for water, due in part to climate effects, is likely to increase pressures on both the availability and cost of irrigation water supplies.”
Additionally, commodity prices may determine if it remains economical to irrigate a crop or not. “As higher irrigated revenues are required to cover the higher costs of production, irrigation returns may be particularly sensitive to commodity price fluctuations, depending on relative profit margins of local irrigated and dryland production,” predicted the report.