Agroforestry supports high bird diversity in European farmland

Abstract

Intensification and homogenization of agricultural landscapes have led to a strong decline in European farmland birds. Agroforestry systems, which were widespread in the past, are regaining attention as they could return structural heterogeneity to agricultural landscapes. However, few studies focus on the effects of such systems on biodiversity and especially bird diversity. We hypothesized that agroforestry systems host a higher alpha and beta diversity of birds compared to open agriculture as well as distinct bird communities. Moreover, we expected that bird communities in temperate Europe and the Mediterranean are differently affected by agroforestry systems. In this study, we assessed breeding bird diversity via audio recordings in nineteen mature agroforestry plots, comprising both silvoarable and silvopastoral systems distributed across seven countries in temperate and Mediterranean Europe. For comparison, bird diversity was also assessed in nearby open agricultural land, forests, and orchards. Bird species richness in agroforestry was more than doubled compared to open agricultural land and similar to the diversity found in forests and orchards. Community composition and within-habitat beta diversity differed between the habitat types and between European regions. While temperate agroforestry systems hosted generalist and woody habitat species, bird communities in Mediterranean agroforestry were composed of species from both open and woody habitats. Beta diversity was significantly higher in agroforestry than in open agriculture in temperate systems but not in the Mediterranean. Our study demonstrates that agroforestry systems represent a valuable habitat for breeding birds in European agricultural landscapes. A wider adoption of these systems could thus contribute to halting and reversing the decline in bird diversity, especially in temperate agricultural landscapes.