Annual land requirements, per person, based on agricultural land type. Kurtz et. al, 2020
When the researchers determined foodshed size based on how Americans eat today, the resulting map varies widely from region to region. Cities in the northeast, southeast, and southwest are more heavily populated than the center of the country, for instance, so they have to travel further to feed everyone.
Foodshed size would shrink, the researchers argue, if people begin to limit consumption of animal-based foods — something climate scientists call for anyway. Two separate recent studies each called for seriously cutting animal products as both a measure against climate change and one toward preserving biodiversity.
In the new study, researchers argue that lowering the amount of animal-based foods a city needs will make it increasingly more regionally self-reliant. Under a vegan or vegetarian diet, many populations could harvest 100 percent of their food within 155 miles (250 kilometers), the study reports.
No man’s land — Under any of the seven diet scenarios the researchers modeled, excess land remains. These areas aren’t used to grow food; what is done with them has big implications for conservation.
Currently, most land not reserved for farming is used to grow crops for biofuel — a US export and billion-dollar industry. If cities were to prioritize local eating, there would be an opportunity to reshape how land is used for American agriculture. For example, those decisions could devote more, or less, land to conservation efforts.
Study author Christian Peters is an associate professor at Tufts University. Peters explained that changing up food systems would have to come along with policy changes.
“It would be important to make sure policies for supporting local or regional food production benefit conservation and create opportunities for farmers to adopt more sustainable practices,” Peters said in a statement. “Policies should also recognize the capacity of the natural resources in a given locale or region–and consider the supply chain, including capacity for food processing and storage.”
Abstract: In the long term, food systems must heed natural resource limits. Localized production and dietary changes are often suggested as potential solutions. However, no U.S. analyses fully evaluate the feasibility to scale localization across a range of diets. We therefore modeled the biophysical capacity for regional food systems based on agricultural land area and productivity, population, and 7 diet scenarios ranging in meat-intensity, from current consumption to vegan. We estimated foodshed size, colloquially known as “food miles” for 378 U.S. metropolitan centers, in a hypothetical nationwide closed system that prioritizes localized food. We found that foodshed size (weighted average distance traveled) for three land types ranged from 351–428 km (cultivated cropland), 80–492 km (perennial forage cropland), and 117–799 km (grazing land). Localized potential varies regionally: foodsheds are generally larger in the populous Northeast, Southeast, and Southwest than in the Northwest and the center of the country. However, depending on consumption of animal-based foods, a sizable proportion of the population could meet its food needs within 250km: from 35%–53% (cultivated cropland), 39%–94% (perennial forage cropland, 100% for vegan), and 26%–88% (grazing land, 100% for ovolacto-vegetarian and vegan). All seven scenarios leave some land unused. This reserve capacity might be used to supply food to the global market, grow bioenergy crops, or for conservation.