Restored marginal farmland benefits arthropod diversity at multiple scales

Abstract

The loss of resource-rich non-crop habitat is a hypothesized driver of arthropod decline on farms, implying recovery with restoration. Alternatively, chronic arthropod loss may limit colonization to abundant taxa, especially crop pests. Here, we test the impact of restoring marginal farmland on agriculturally important arthropods on 13 conventional farms across a 10,000 km 2 region of central North America with approximately 92% crop cover. We examined local richness by habitat (crops, restored prairie, remnant forest), spatial turnover among habitat and farms, and regional comparisons between farm and non-farms using iNaturalist data. Sampling approximately 13,000 individuals identified to family or lower, restored prairie had twice the abundance of arthropods compared to crop and forest, with 44% of all families detected, 66% of beneficial families, and 94 unique taxa despite their recent construction (<10 years) and small size (~9.6% of farm area). There was some compositional overlap between crop and prairie, while farm forest had mostly unique taxa. Larger restored areas supported more diverse and taxonomically uniform arthropod assemblages, while crop fields were family-depauperate with primarily herbivorous taxa. Unexpectedly, the abundance and richness of arthropods between farms with restored habitat and non-farm areas regionally were similar, although farms possessed more herbivorous species and fewer butterflies and aquatics. The extensive and rapid colonization of restored habitat by beneficial arthropods implies that conventional farms may be habitat limited for many taxa. Our work supports calls for farm redesign that includes habitat reconstruction, which can support arthropods with known benefits to food production.

Safeguarding pollinators requires specific habitat prescriptions and substantially more land area than suggested by current policy

“…Given that many habitat losses in North America are often the result of the conversion of natural land to agricultural uses 38 , 39 , and that agricultural expansion has resulted in significant loss of phylogenetic diversity in bee communities 40 , it is important that environmental policy in agricultural landscapes consider addition, restoration or creation of wetland habitats. Evidence-based conservation policies for supporting pollinators may also deliver other biodiversity benefits, for example providing suitable habitat for other beneficial arthropods (e.g., spiders and parasitoid wasps that can provide crop pest bio-control 41 ), birds and other wildlife in the landscape. The ecosystem services provided by wetlands extend far beyond pollinators—wetlands increase the water table height and therefore the quantity of water available for crop irrigation, improve drinking water quality, flood mitigation and habitat for other wildlife, including other species-at-risk 42 – 44 .…”