Small field islands systems include a large proportion of the regional orthopteran species pool in arable landscapes

Abstract

The tendency of species richness to increase with patch area is one of the most robust empirical generalisations in ecology and its logic drives conservation actions. Indeed, preference is often given to conserving large, highly connected areas over small isolated patches. However, small habitats have been shown to be important biodiversity refuges in managed landscapes. Field islands are small remnants of natural habitat patches surrounded by cropland. While their island-like position in a species-poor crop field makes them potentially strategic habitats for biodiversity conservation, they have not received much attention in ecological studies. We investigated how local (i.e. field island area and habitat diversity) and landscape factors (i.e. proportion of arable land) affected orthopteran species richness, community mean dispersal and habitat specificity in 71 field islands in central Sweden. We found that despite low numbers of species per field island, due to their intrinsic small size, taken together, a system of small field island increased species richness and included a large proportion of the regional species pool in the arable landscape in central Sweden. Furthermore, we found that patch area and habitat diversity determined orthopteran community composition in field islands. More diverse and, to a lesser extent, larger field islands benefit sedentary and habitat specialist species. This study shows that more care should be taken to incorporate and potentially also prioritize small and permanent habitat patches in the management of agricultural landscapes. The protection of field islands with diverse habitats may be important for the maintenance of sedentary and specialist species.