Over two-thirds of cropland in the United States is devoted to the production of just four crop species, raising concerns that the increasingly homogenized American agricultural landscape will facilitate widespread disease and pest outbreaks that could compromise national, and international, food supplies. As a first step in developing a national agricultural risk assessment, we employed a graph-theoretic approach to examine the connectivity of croplands across the U.S. Dispersal transmission costs were calculated based on harvested acres of the four crop species to evaluate the likelihood of pathogen or pest spread across a range of spatial scales.

Results/Conclusions  

For organisms capable of overcoming high transmission costs, maize and soybean are highly connected at a national scale, compared to the more isolated regional production patterns of wheat and cotton. Determining the spatial scales at which connectivity becomes disrupted, as indexed by thresholds in transmission costs, helps target rapid-response regions and the development of policies to strategically enhance agricultural landscape heterogeneity.