Community dynamics under environmental change: how can next generation mechanistic models improve projections of species distributions?

Abstract

Environmental change is expected to shift the geographic range of species and communities. To estimate the consequences of these shifts for the functioning and stability of ecosystems, reliable predictions of alterations in species distributions are needed. Projections with correlative species distribution models, which correlate species’ distributions to the abiotic environment, have become a standard approach. Criticism of this approach centres around the omission of relevant biotic feedbacks and triggered the search for alternatives. A new generation of mechanistic process-based species distribution models aims at implementing formulations of relevant biotic processes to cover species’ life histories, physiology, dispersal abilities, evolution, and both intra- and interspecific interactions. Although this step towards more structural realism is considered important, it remains unclear whether the resulting projections are more reliable. In this opinion paper, we discuss how the discrepancy between demand for structural realism on the one hand and related knowledge gaps on the other hand affects the reliability of mechanistic species distribution models. We argue that omission of relevant processes potentially impairs projection accuracy, particularly if species range shifts emerge from species and community dynamics, whereas insufficient knowledge that limits model specification and parameterization, as well as process complexity, increases projection uncertainty. We propose a protocol to improve and communicate projection reliability, combining modelling and empirical research to efficiently fill critical knowledge gaps that currently limit the reliability of species and community projections.