Authors: Korányi, Dávid; Egerer, Monika;Rusch, Adrien;Szabó, Borbála;Batáry, Péter;

Biological control is a major ecosystem service provided by natural enemies, especially in densely populated areas where chemical plant protection poses severe risks to human and environmental health. However, the impact of urbanization on this service and the abundance patterns of relevant functional groups (herbivores, predators, and parasitoids) remains contested. By performing three hierarchical meta-analyses on 51 relevant studies, we showed that advancing urbanization leads to outbreaks of sap-feeding insects, declining numbers of predators with low dispersal abilities, and weakened overall biological pest control delivered by arthropods. In addition, we found a strong contrast between species- and community-level observations for both herbivore and natural enemy abundances with a significant positive effect of urbanization on herbivore species and a marginally significant negative effect on natural enemy communities. Our results suggest that sedentary predators may have the potential to effectively regulate sap-feeders, one of the most important pests in urban environments. A well-connected network of structurally diverse and rich green spaces with less intensive management practices is needed to promote natural plant protection in urban landscapes and sustainable cities.