Landscape-level synergistic and antagonistic effects among conservation measures drive wild bee densities and species richness

Pollinators face significant global decline due to agricultural intensification. The current focus on local measures to counteract this negative trend may miss processes at larger spatial scales and interactive effects between different measures. It remains unclear whether multiple combined landscape conservation measures (LCMs) will be more efficient (synergistic effect) than single LCMs, reduce each other’s effectiveness (antagonistic effect) or sum together (additive effect) to promote biodiversity. We assessed the interactive effects of three LCMs, i.e. organic crops, annual flower fields and perennial semi-natural habitats, on wild bee species richness and densities at the landscape scale. Notably, we observed a synergistic effect between organic crops and perennial SNH, likely due to their provision of complementary resources in agro-ecosystems. However, antagonistic effects were more common, e.g. between annual flower fields and organic farming, indicating that mixing LCMs to promote wild bees requires judicious evaluation to maximize complementary benefits and reduce redundancy.