Biodiversity may wax or wane depending on metrics or taxa

Abstract

<i>Introduction</i>: Biodiversity changes have proven surprisingly complex to estimate and understand. While there are negative trends at a global scale such as the substantial losses of vertebrate species (1), changes at local scales may show large variation, with no clear overall trend (2, 3). Because assessing and improving the status of biodiversity are at the core of international agreements such as the Convention on Biological Diversity and the associated Aichi Biodiversity Targets for 2020 (4), we need to know when trends in biodiversity may differ and the causes of such differences. In PNAS, Magurran et al. (5) report that different components of biodiversity do not have the same trends over time in tropical freshwater ecosystems, and that these trends differ among taxonomic groups (fishes, invertebrates, and diatoms).