The context-dependency of trophic cascades: A global meta-analysis of terrestrial large carnivore effects

Apex predators structure ecosystems through trophic cascades, yet the global magnitude and environmental drivers of these effects across diverse biomes remain a subject of intense debate. Synthesizing data from 113 studies, we find a substantial overall cascading effect (mean lnRR = 1.10) driven by terrestrial large carnivores. However, we reveal that this top-down effect is highly context-dependent, peaking in arid, low-productivity environments and attenuating in biomes with high precipitation and vegetation growth. We also resolve a central dispute in community ecology by demonstrating that the perceived strength of cascades depends heavily on research design. Observational studies yield significantly larger effect sizes than experimental manipulations, highlighting a methodological trade-off between capturing landscape-level ecological realism and achieving localized causal inference. Furthermore, the current evidence base exhibits pronounced geographic and taxonomic skews, with a disproportionate focus on North American and Australian canids. Together, these findings indicate that terrestrial trophic cascades are less universal than often assumed. Accurately forecasting the ecological consequences of carnivore loss or recovery requires moving beyond generalized models towards context-explicit and methodologically integrated frameworks.