Farming with nature: A case study of ALUS Canada farms and the practice of ecological intensification

Background/Question/Methods: The expansion of intensive agricultural practices has been a key driver of biodiversity loss, including insect species abundance and richness, and the ecosystem services on which we rely. One model that has been proposed to help tackle this farm management paradox is so-called “precision agriculture”; a strategy that includes conversion of marginal lands on farms to native species-rich prairie grassland, which has been adopted by ALUS Canada. The objective of this study was to provide a comprehensive arthropod survey on these farms which has not been attempted and therefore lacks information regarding recent prairie restoration efforts. The main questions my study addresses: 1) How does management strategy (ALUS vs conventional) effect beneficial species richness and abundance? 2) What local and landscape factors contribute to greater beneficial insect functional groups (pollinators, predators, parasitoids) that deliver vital ecosystem services? 3) How does cover type influence insects on agricultural fields? Field research was undertaken on 23 farms located in Southern Ontario to examine effects of local and landscape factors on the community structure and function of early-season arthropod groups, and ultimately how this influences crop damage. All arthropods were identified to family and categorized into 9 functional groups.

Results/Conclusions: Results show that these grassland borders can increase beneficial arthropod abundance, including natural enemies of many pests. Significantly more predators, parasitoid wasps and pollinators were captured in prairie cover versus crop cover or woods. Responses to prairie borders varied across specific functional groups but mainly depended on age of prairie, plant richness and plant biomass. The presence of tallgrass prairie on ALUS farms had spill-over effects into crop fields, where predator abundance increased in interior parts of the crop, where conventional farms limited predator abundance to edges. Crop damage was also less on ALUS farms in terms of indirect leaf damage, presumably from natural enemies decreasing herbivory. Overall, beneficial insect abundance, richness and total abundance was greater on ALUS management farms then conventional farms, which was driven by the increase in local habitat diversity and resources from prairie grassland borders. This study provides a clear demonstration that precision agriculture, which supports ecosystem services, is compatible with, and even increase beneficial insect taxa to spill-over into crop fields.