A Systematic Review of the Benefits and Costs of Bird and Insect Activity in Agroecosystems

Wild fauna occur in every agroecosystem and their interactions with crops can influence yields positively or negatively. Research on the impact of fauna activity on agricultural production focuses mostly on either the costs (e.g. crop damage) or benefits (e.g. pollination) of this activity, with few studies addressing cost-benefit trade-offs in the same context. This has resulted in an incomplete understanding of the implications of fauna activity in agroecosystems. Through a systematic review of the literature, we connect disparate studies to promote a more holistic approach to research on wild fauna in agriculture. We identified 281 studies that quantified a cost and/or benefit of fauna activity in crop systems. Overall, 53.0 % of studies examined the costs of insect and/or bird activity, 37.7 % of studies examined benefits and just 9.3 % of studies covered both costs and benefits of insect and/or bird activity simultaneously. Most birds studied were omnivorous (44.8 %), granivorous (29.0 %) or insectivorous (16.6 %), while insect studies focused on pollinators (42.2 %) or borers (17.5 %). There were clear geographic patterns for studies, with a bias towards studies of the costs of bird activity in North America and studies of benefits in Central America/Caribbean. Most studies on benefits occurred in perennial crops and most cost studies in annual crops. Our results highlight the disjointed nature of research into the cost–benefit trade-offs of fauna activity, and it is essential that future studies examine these trade-offs in order to develop sustainable agricultural strategies that limit production losses while maximising the delivery of ecosystem services from fauna.