Semi-Natural Habitats Buffer the Effects of Crop Diversification on Arthropod Pest Control Services in Agricultural Landscapes.

Crop diversification is a promising strategy to strengthen pest control services in agricultural landscapes. Diversifying crops may limit pests through host crop dilution or by enhancing top-down control by their enemies. However, crop diversification may also benefit generalist pests through higher resource continuity. Using a large-scale dataset encompassing 742 landscapes across 13 countries, we assessed the impact of landscape-scale crop diversity on the abundance of natural enemies, the potential for biological control, and insect pest abundance. Crop diversification did not increase the overall abundance of natural enemies or the potential for biological pest control. Instead, crop diversity primarily favoured the abundance of specialist natural enemies and pests in highly simplified landscapes, an effect that was reduced in landscapes with high proportions of semi-natural habitats. Lastly, low proportions of host crops in the landscape were associated with higher abundances of natural enemies. Taken together, our results indicate that crop diversification is not a 'one size fits all' strategy to control agricultural pests, and that other landscape characteristics, such as high amounts of semi-natural habitats, must be considered to enhance biological pest control services.