Landscape structure regulates pest control provided by ants in sun coffee farms.
Ants play a fundamental role in coffee pest control. Despite this, there is a lack of understanding about how landscape configuration and composition regulate the ecosystem service provided by ants in sun coffee farms within highly fragmented landscapes. We measured whether landscape structure influences ants' ability to regulate coffee berry borer (CBB) in sun coffee farms in Southeastern Brazil. Considering the ecological interactions between ants and CBB at three different stages of pest control (reduction of CBB presence, CBB infestation, and CBB bean damage), we measured pest control among 10 landscapes that represented a gradual difference in forest and coffee cover. We manipulated ants through exclusion experiments and tested whether interactions between ants and different landscape structure metrics (distance to forest fragments, 2-km-level forest cover, and 300-m-level forest and coffee cover) influenced pest control. The presence of ants reduced CBB presence and CBB damage by up to 40%. We show how pest control service indicators change depending on the landscape level. The probability of CBB presence increased with expanding coffee and forest cover at the 300-m-level but decreased at the 2-km-level. CBB infestation reduced further after 25 m from forest edges, suggesting ants that provide these ecosystem services are adapted to matrix conditions in sun coffee farms. Ants reduced CBB presence, CBB infestation, and CBB damage in landscapes with at least 40% 2-km-level forest cover. Beyond this threshold, there is a turning point for ecological processes involved in pest control. Synthesis and applications. This is the first long-term branch-level exclusion experiment to present strong evidence of ants as efficient providers of pest control in sun coffee farms. We show how landscape structure modulates key ecological processes involved in three different ant-CBB interactions that regulate CBB populations. Forest cover measured at different landscape levels yielded different results for CBB presence, emphasizing the importance of multi-scale studies for landscape management. Considering surrounding forest cover and crop proximity to forest fragments in planning the spatial arrangement of coffee farms can thus both improve pest control as well as contribute to biodiversity conservation.