Farmland diversification shapes bird-mediated trade-offs and synergies

Elissa M. Olimpi, Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, Karina Garcia and David J Gonthier, Entomology, University of Kentucky, Claire Kremen, Institute of Resources, Environment and Sustainability, Dept. of Zoology and Biodiversity Research Center, University of British Columbia, Vancouver, BC, Canada, William E. Snyder, Entomology, University of Georgia, Athens, GA, Erin E Wilson-Rankin, Department of Entomology, University of California, Riverside, Daniel Karp, Wildlife, Fish, and Conservation Biology, University of California, Davis, CA

Background/Question/Methods: Working landscapes can be managed to support conservation and deliver multiple benefits to society by implementing biodiversity-based management strategies. However, such approaches can be associated with both benefits (services) and costs (disservices). Farmland birds can suppress insect pests, but may also consume beneficial insects, damage crops, and potentially carry foodborne pathogens. As bird communities shift in response to farming practices, so too do the benefits and costs from birds. To inform management interventions that promote multifunctional bird communities, we investigated how farmland diversification influences the services and disservices provided by wild birds on 21 California strawberry farms. Specifically, we coupled 285 bird surveys with next-generating sequencing and targeted PCR of ~1,000 fecal samples from 55 species to determine which individuals consumed pests, natural enemies, and crops and carried foodborne pathogens. We used a combination of surveys and experiments to validate that bird diets directly relate to the provisioning of ecosystem services and disservices. Then, we explored how farming practices shape bird communities and the bundles of ecosystem services/disservices that they provide.
Results/Conclusions: Our research revealed that bird-mediated ecosystem services and disservices are shaped by interactions between local farming practices and landscape context. We found that the amount of seminatural habitat surrounding each farm was the single most important driver of ecosystem services and disservices. Increasing seminatural habitat around farms was associated with more diverse and multifunctional bird communities. However, not all tradeoffs were minimized in landscapes with more habitat. For example, the tradeoff between pest and natural enemy consumption was minimized on farms with little surrounding seminatural habitat. Overall, our work shows that specific farming contexts can exacerbate or mitigate tradeoffs by causing changes in the relative abundance of species that are more harmful or beneficial. Although growers are often pressured to remove noncrop habitat to reduce food-safety risks, our work suggests that conserving habitat can support bird conservation, mitigate food-safety risks, and decrease crop damage from birds. More broadly, by considering the multiple roles that communities play in ecosystems, managers can simultaneously maximize services and minimize disservices.