Exploration of multiple post-extinction compensatory scenarios improves the likelihood of determining the most realistic ecosystem future

Abstract

A research agenda is currently developing around predicting the functional response of ecosystems to local alterations of biodiversity associated with anthropogenic activity, but existing conceptual and empirical frameworks do not serve this area well as most lack ecological realism. Here, in order to advance credible projections of future ecosystems, we use a trait-based model for marine benthic communities to inform how increasing trawling pressure changes the biological-mediation of seabed functioning. Our simulations reveal that local loss of species, and the associated compensatory community response, lead to multiple and disparate biogeochemical alterations that are contingent on relative vulnerabilities to extinction, environmental and biological context, and the level of functional redundancy within replacement taxa. Consequently, we find that small changes in faunal mediation caused by community re-organisation can disproportionately affect some biogeochemical components (macronutrients), whilst having less effect on others (carbon, pigments). Our observations indicate that the vulnerability of communities to future human-induced change is better established by identifying the relative magnitude and direction of covariance between community response and effect traits. Hence, projections that primarily focus on the most common or most productive species are unlikely to prove reliable in identifying the most likely ecological outcome necessary to support management strategies.