With intensifying anthropogenic disturbances, coastal habitats dominated by foundation species such as seagrass, corals, and salt marsh plants have changed drastically during the past century, becoming smaller, fragmented, and structurally degraded. Yet, our understanding of how these changes impact key ecosystem processes such as consumer-resource interactions, is still limited. We conducted a systematic review and meta-analysis of 195 papers and 828 studies to examine how ongoing habitat changes (i.e., patch size reduction, fragmentation per se, increased habitat edge, reduced habitat connectivity, and loss of structural complexity) are modifying predation and herbivory pressure in key coastal habitats (e.g., seagrass bed, coral reef, salt marsh, oyster reef, mangrove forest, and macroalgal bed).
Results/Conclusions
Our analysis revealed an overall increase in resource consumption associated with ongoing habitat changes, with this effect consistent across different trophic levels (primary, secondary, and tertiary or higher-level consumers). Patch size reduction increased overall resource consumption and herbivory, but not predation. While fragmentation per se had no effect, both herbivory and predation were strongly elevated at habitat edges. Decreasing connectivity between different habitats increased herbivory, but reduced predation. Finally, loss of structural complexity within the same habitat type increased predation by tertiary or higher-level consumers only, whereas shifts toward different habitats with lower structural complexity increased resource consumption for all trophic levels. These results provide interesting contrasts with patterns from recent reviews and meta-analyses of terrestrial studies, where similar types of habitat change tend to reduce or do not affect the strength of consumer-resource interactions. We hypothesize that this difference may be attributed to a higher prevalence of habitat generalists among marine consumers, whose spatial distribution and foraging activity may be negligibly or even positively affected by fragmented seascapes. In conclusion, our study suggests that ongoing changes in seascape and habitat structure have the potential to modify marine consumer-resource interactions, and therefore have important implications for the resilience of coastal habitats under global change.