Losers and winners: responses of grassland arthropods to land-use components

Intensified land-use in grasslands reduces biodiversity, particularly affecting arthropod populations. However, responses of individual species vary depending on their ecological traits and habitat requirements. Some species may tolerate or even benefit from intensive land-use, while others, particularly specialists or those with narrow niches, are likely to be negatively affected. We used a quantitative niche model to evaluate species-specific responses to land-use intensity in four arthropod orders common in grasslands: Araneae, Coleoptera, Hemiptera and Orthoptera. From 2008 to 2018, a total of 214 416 individuals across 1352 species were collected on 150 grassland plots across three regions of Germany. The effects of mowing, fertilizing, and grazing on species occurrence and abundance were evaluated by their niche optima to identify winners, losers, and neutrals. Fertilizing showed the fewest winners (6%) as well as the most losers (29%) with all orders having the highest proportion being negatively affected, whereas grazing showed the most winners (10%) and fewest losers (10%). Nevertheless, most species showed neutral responses (71%). The niche optimum of grazing favored smaller species, whereas mowing and fertilizing favored larger species. Herbivores were particularly sensitive to fertilizing. Comparison with the Red List revealed that species under mowing exhibited lower niche optima with higher-risk categories, which was also reflected in declining population trends. This study highlights the high variation in species-specific responses of arthropods to the different components of land-use, showing overall three times as many loser species as winner species. This emphasizes the need for conservation strategies tailored to vulnerable species. Balancing land-use strategies with biodiversity conservation in land-use policies is essential to preserve arthropod diversity and enhance ecosystem resilience in grasslands.