4: 130 years of agricultural intensification has decreased the occurrence of bumble bees in the North American Midwest

Recently documented insect declines suggest that agricultural expansion and productivity-focused intensification are a putative driver for the observed declines. However, this hypothesis has yet to be formally tested due to a lack of historical data on agricultural land-use change and insect occurrence. Using large, spatiotemporal sets of bumble bee and agricultural records, we show that agricultural intensification, specifically an increase in cropland extent, as well as a decrease in crop richness and perennial habitat, are associated with decreasing occurrence of bumble bee species in the agriculturally intensive Midwest, USA. Yet, we found positive associations between bumble bees and crop richness, even in areas where agriculture is spatially extensive. Our findings suggest that insect conservation and agricultural production may be compatible, with increasing on-farm and landscape-level crop diversity predicted to have positive effects on bumble bees.