Moderate sheep grazing increases arthropod biomass and habitat use by steppe birds

Abstract

Open semi-natural ecosystems have been historically shaped by anthropogenic land-use, and the abandonment or intensification of these activities implied a detrimental alteration of their landscapes. Extensive sheep grazing has gradually decreased during the 20th century in Mediterranean steppes, triggering changes across all taxa. Here, we address the effect of sheep grazing on both arthropod biomass and space use by insectivorous steppe birds, using an endangered passerine as a model species. We found that biomass of different arthropod groups peaked at intermediate levels of grazing, and that both short-term grazing (affecting arthropod biomass) and long-term grazing (affecting vegetation structure) explain space use by insectivorous birds, whereas only long-term processes are decisive for bird territory establishment. Our results emphasise the role of sustained moderate grazing intensity in the conservation of steppe biodiversity. In the current decline context of extensive sheep grazing, agricultural policies should prioritise these practices to ensure the persistence of open semi-natural ecosystems.