Authors: Neff, Felix; Korner-Nievergelt, Fränzi;Rey, Emmanuel;Martínez-Núñez, Carlos;Herzog, Felix;Knop, Eva;

Reports on insect decline have raised considerable concerns in the scientific community and the public. Climate change and land-use change are considered to be main drivers of insect decline, but their combined and interactive effects on insect populations are poorly understood. Studies of adequate temporal, spatial and taxonomic scale are largely missing. We used almost 1.5 million species records to analyze insect occupancy trends (butterflies, grasshoppers, dragonflies) in Switzerland across a period of 40 years (1980–2019). We disentangled main and interactive effects of climate and land-use change on species trends, which was possible because Switzerland can be divided into different climatic regions and along an elevational gradient. Our results show considerable declines but also increases of species occupancies. Changes at regional scale were best explained by climate warming, showing the predominant role of climate change in driving insect community changes in the last 40 years. Land-use change was less strongly linked to species trends, indicating that recent efforts to reduce negative land-use impacts had little large-scale effects. Along with interactive climate and land-use change effects, this shows that further efforts in large-scale land-use management are indispensable to halt biodiversity loss in the coming, further warming century.