Trophic regulation constrains ecosystem carbon accumulation under global change.

Abstract

Global change is rapidly reshaping the ecosystem carbon cycle, yet how trophic regulation-a fundamental driver of ecosystem biogeochemical cycling-mediates these responses remains poorly understood. Here we present a global synthesis of interactions between trophic regulation and major global change factors (GCFs: fertilization, warming, fire, increased precipitation, drought, and multiple GCFs), integrating 708 paired full-factorial experimental tests across 132 studies worldwide. We show that while GCFs alone increase ecosystem carbon stocks by 27% on average, their interactions with herbivores drive carbon losses of 23%, reversing the potential gains from individual GCF effects. Carbon losses are functionally localized in aboveground plant, litter, and microbial biomass carbon, with the most pronounced depletion occurring in the tropics, drylands, aquatic systems, and restoring ecosystems. Herbivore body size emerged as a directional trait shaping these outcomes, with small-bodied herbivores exerting disproportionately negative effects. Importantly, while excluding herbivores enhances carbon accumulation under global change, this sequestration benefit comes at the cost of reduced plant diversity, revealing an inherent trade-off between carbon-centric objectives and ecosystem integrity. Together, our findings demonstrate that carbon sequestration potential under global change cannot be evaluated independently of trophic regulation. Accounting for animal-mediated feedback is therefore essential for realistic Earth system model projections and for developing nature-based solutions that align climate mitigation with biodiversity conservation.