Top-down effects dominate the relationship between plant-herbivorous insect interactions and ecosystem stability.

Consumptive interactions across trophic levels underpin ecosystem stability. Although theoretical and experimental studies have examined the diversity-stability relationship, empirical evidence linking trophic interactions to ecosystem stability remains limited. Here we evaluate how trophic interactions relate to stability across 430 plant-herbivorous insect networks from temperate and tropical ecosystems. We quantified interaction indicators alongside ecosystem resistance and resilience under drought and wet events. Higher plant diversity was associated with drought resistance but with reduced resilience, and these relationships weakened after accounting for sampling and environmental covariates. In contrast, drought resistance increased with network modularity, whereas resilience decreased with robustness, although these patterns were absent in temperate forests. Diversity and interaction indicators did not predict stability under wet events. Although both directions of trophic interaction-stability relationships were significant, the pathway from trophic interactions to stability (top-down) was stronger than the reverse. Our findings provide large-scale empirical evidence that top-down effects probably dominate the relationship between plant-herbivorous insect interactions and ecosystem stability under climate change.