There’s a clear link between high agricultural diversity and crop resilience. Monocultures are more susceptible to disease, and pests are harder to control (at least using natural methods).
Diverse agriculture offers opportunities for “nutrient cycling” between plants, and “provides stability in an area to assure food sustainability,” says Jonathan Aguilar, lead author of a new paper on diversity in the U.S farm belt.
The study offers a 34-year perspective on shifts away from diversity–with fewer types of crops in particular areas–and shifts toward it. The “Heartland Resource Region”–covering Illinois, Iowa, Indiana, and parts of Ohio, Missouri, Minnesota, South Dakota, Nebraska, and Kentucky–has decreasing diversity. But parts of Louisiana, Mississippi, Kentucky, and Arkansas had much higher crop diversity in 2012 than in 1978.
Researchers at Kansas State University, North Dakota State University, and the U.S. Department of Agriculture took data from the U.S. Census of Agriculture covering what’s planted on the 408 million acres of cropland out there. Parts of Washington, Oregon, Idaho, California, Arizona, Texas, Florida, Georgia, South Carolina, Wisconsin, Michigan, Maine, New Jersey, and Pennsylvania have the highest diversity in the country today.
It’s not surprising or unreasonable for farmers to concentrate on one or two crops. Growing in bulk reduces costs (for example, because farmers need less equipment or can win better prices for seeds). And, as the paper says, farmers aren’t necessarily concerned with the “ecosystem benefits of diverse cropping systems.”
Using county-level data, the paper also looks at changes within states, offering a picture of what happens at a more local level. Look, for example, at North Dakota.
“Technology, such as no-till seeding techniques and disease pressures, may have increased diversity in the central portion of the state,” says USDA’s John Hendrickson. But “changes in genetics and technology and market forces may have reduced diversity in the southeast corner of the state.” Diversity was not a function of a single factor, but lots of them, Hendrickson adds.
The question for policymakers is how to balance the interests of farmers who may want to focus on one or two crops and the wider environment, which needs to be diverse to be most productive.
“Policies aimed at stabilizing revenues by supporting a particular crop can reduce diversity,” the paper says. But “policy changes that encourage crop diversity may be needed to support efforts to ensure future food security.”