Climate regulates the suppression of insect herbivory by livestock grazing at a continental scale

Grasslands represent one of the most extensive ecosystems on Earth, yet they are undergoing profound ecological change driven by livestock grazing. Herbivorous insects play a fundamental role in terrestrial food webs and are essential for regulating grassland ecosystem functioning. Yet, the ecological impacts of grazing on insect herbivory and how these are shaped by climate remain illusive. We demonstrate that grazing consistently reduces community-wide insect herbivory, using a continental-scale study across 14 paired sites in China’s major steppes. This pattern likely arises from grazing-induced shifts in plant community composition towards more defended plant taxa. Importantly, we find that climate modulates the effects of grazing on insect herbivory: grazing strongly suppressed herbivory in arid and hot steppes but had minimal impact in regions of lower temperature and aridity. Our study reveals a key contingency in grazing effects, showing that climate fundamentally regulates top-down control of herbivory. This knowledge should be integrated into future grassland conservation frameworks.