Land use intensification transforms grassland arthropod communities: A few winners expand but most species disappear

Arthropod declines pose existential threats to terrestrial ecosystems but remain poorly understood. In human-dominated habitats such as managed grasslands, arthropod communities are thought to decline as a result of land-use intensification. However, studies that link land-use intensity to arthropod species richness, abundance and composition have found mixed results. These inconsistencies may stem from differences in the investigated intensification levels or arthropod communities, as different species may show different responses to land-use change. We show that effects of land-use intensification on arthropod communities can be understood better by examining the distributions of individual species along land-use intensity gradients. We sampled multiple arthropod groups along a wide gradient of grassland productivity as a proxy for land-use intensity. Species richness halved from low to high productivity levels, but overall abundance remained stable because increasing Diptera numbers counteracted strong declines in other orders. Dissimilarity metrics failed to reveal a substantial change in species composition that was shown in individual species' distributions. While low-productivity grasslands supported many species that were confined to narrow productivity ranges, high-productivity grasslands were dominated by a few widely occurring species. Overall, 56 % of all species declined or disappeared as land-use intensified at low-to-medium intensity levels (‘losers’); 35 % preferred intermediate intensities, and only 9 % profited from high-intensity management. These ‘winners’ probably sustain overall abundance levels in high-productivity grasslands. Such large changes in species composition could have significant consequences for ecosystem functioning, necessitating further experimental studies. The uneven distribution of biodiversity losses implies that ecological restoration should focus on low-intensity grasslands.