A biogeographic–macroecological perspective on the rising novelty of the biosphere in the Anthropocene

The concept of novel ecosystems has been discussed for over more than a decade to describe ecosystems that have an altered species composition and function, such that the community has crossed a threshold forbidding a return to its historical state. While spatial and temporal community compositional change has been well studied in biogeography, studies on novel ecosystems in a modern context are few and tend towards classifying novelty based on a static baseline. Given that the abiotic and biotic drivers of novelty are in a state of rapid change, and reaching levels unprecedented within the last hundred thousand to million years, defining such a threshold requires additional thought. Here, we discuss a biogeographical–macroecological perspective on novel ecosystems, exploring how such a threshold for novelty can be defined in an environment undergoing progressive global change and suggesting pathways through which the emergence and spread of novelty can be further explored, understood and managed.