Anthropogenic activities could push the Earth outside of a safe operating space for humanity. The limits to this safe space, known as planetary boundaries, represent a powerful idea that is gaining some support in scientific and environmental circles. Loss of biodiversity has been identified as one of these boundaries where extinction trends are pushing the Earth system far outside of a safe space.
Georgina Mace, from the Centre for Biodiversity and Environment Research, University College London, and co-workers review the evidence for the identification of a biodiversity planetary boundary. They find that the conventional measures (extinction rate and species richness) are weak metrics for the identification of a safe operating space that do not scale up well, for example, from local to global levels. The authors propose instead three facets of biodiversity on which the identification of a boundary could be based: the genetic library of life (a measure of phylogenetic diversity); diversity of functional types (particularly those functions relevant to key ecosystem processes); and biome integrity (the condition and extent of biomes). The role of biodiversity in mediating other planetary boundaries is also emphasized.
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Brown, A. Planetary boundaries. Nature Clim Change 5, 19 (2015). https://doi.org/10.1038/nclimate2485