COS 89-5
Spatial heterogeneity in the relationship between landscape simplification and insecticide use
Agrochemicals have numerous negative impacts on human and environmental health, and thus their efficient use is an economic, ecological and public health priority. It is thought that simplified landscapes result in disproportionately higher insecticide use due to the lack of natural enemies controlling insect pests and the higher connectivity between crop fields. However, empirical tests of this theory have found ambiguous results. Here we explore the spatial variation in the relationship between landscape simplification and insecticide use at a national scale. We use data from five USDA Census of Agriculture years spanning two decades (1987, 1992, 1997, 2002, 2007) for almost 3000 counties across the continental United States.
Results/Conclusions
We find that the proportion of county in cropland, our metric for landscape simplification, is highly variable spatially and temporally. Landscape simplification is consistently positively correlated with insecticide use in some regions, completely uncorrelated in others, and switches between strong positive, negative and null results in still other regions. This spatiotemporal variability is not explained by annual weather nor can it reflect systematic differences in pesticide regulation. This national perspective indicates that the relationship between landscape simplification and insecticide use is dynamic and that national land use policy would benefit from actions that adequately reflect the spatiotemporal differences in the importance of landscape structure to insecticide use.