Not so simple: Landscape simplification does not consistently drive insecticide use

Background/Question/Methods

The increase in agricultural production over the past forty years has corresponded to changes in land use patterns, often resulting in simplified landscapes composed of large swaths of monocultures separated by small fragments of natural lands. There are concerns that these simplified landscapes are more susceptible to insect pest pressure due to the loss of natural enemies and the increased size and connectivity of crop resources, and a recent analysis using a single year of data (2007) suggests this increased susceptibility results in increased insecticide use. Here I ask, does landscape simplification consistently drive insecticide use or is 2007 an anomalous year? Using a combination of cross-sectional and panel data models I re-evaluate the proposed relationship between landscape simplification and insecticide use utilizing five USDA Census of Agriculture years (2007, 2002, 1997, 1992, 1987) for seven Midwestern states composed of over 560 counties.

Results/Conclusions

I find that while the coefficient on proportion of county in cropland, my metric for landscape simplification, is positive and significant in the 2007 analyses, that relationship is absent or reversed in prior census years and in all years analyzed together. It is evident from this study that landscape simplification is not a consistent driver of insecticide use and that the main drivers of insecticide use are not reliably identified using single time period studies.