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

Abstract

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.

Unravelling the functional and phylogenetic dimensions of novel ecosystem assemblages

“…from 1950 to the present) can be used to focus on changes in taxonomic composition owing to anthropogenic factors such as the introduction of non-native species [21,22,81,92,93] or the degradation of environmental conditions [21,22,81,94]. Alternatively, a multi-century approach could be taken [79], like that used in many palaeoecology studies, which determine how different past assemblages are from a modern reference baseline [77,78,88,95,96] to focus on the lasting impacts of large-scale environmental phenomena. Lastly, a geological time frame could also be used, like contrasting compositional changes before and after Late Quaternary extinctions of megafauna [97][98][99], to assess the adaptation capacity of species.…”

“…Lastly, a geological time frame could also be used, like contrasting compositional changes before and after Late Quaternary extinctions of megafauna [97][98][99], to assess the adaptation capacity of species. In all these cases, it is essential to ensure that the contrast encapsulates species pools that change owing to ecological rather than evolutionary processes [23,79].…”

“…are we managing for composition, services or both?). The second question is, as reviewed in [79], which 'historical' version of a system should we consider the 'baseline'? Specifically, near-sighted views on a historical state might result in shifting baselines [79,[141][142][143], a well-recognized problem in conservation science, mainly when it is not possible to separate the impact of recent anthropogenic-driven environmental change from the natural dynamics of the system [144][145][146].…”

“…The second question is, as reviewed in [79], which 'historical' version of a system should we consider the 'baseline'? Specifically, near-sighted views on a historical state might result in shifting baselines [79,[141][142][143], a well-recognized problem in conservation science, mainly when it is not possible to separate the impact of recent anthropogenic-driven environmental change from the natural dynamics of the system [144][145][146]. Further, given ongoing climate changes, it may be that such baselines are no longer viable even when disturbance or other anthropogenic impacts are mitigated; indeed, the palaeoecological record has been used to challenge the notion of static baselines in general [147].…”

“…Determining the novelty between two points in time or space describes an ecosystem property (see box 1) dependent on the spatio-temporal context used to define the change [79]. As per [24], we suggest using the concept of novelty (novelty sensu stricto, see box 1) to describe this change.…”