Welcome to the Homogenocene? Trajectories of change in global freshwater fish biodiversity during the Anthropocene: evidence from tropical East Asia

Interactions between climate change and anthropogenic stressors such as poor water quality and habitat degradation have had deleterious consequences for freshwater biodiversity, enhancing the spread of non-native species tolerant of a range of conditions, while reducing the resilience of native species. Analysis of freshwater fishes (Actinopterygii) reveals a gradual rise in the proportion of non-native species, and the homogenization of biotas since the start of the Anthropocene has accelerated in recent years. This process has been more apparent in some regions, but after a slight lag, less impacted regions, such as East Asia, are catching up, and the greater prevalence of non-native species has increased assemblage homogeneity. Using examples from human-dominated landscapes in tropical East Asia, especially China, we describe the increasing dominance of non-native fishes (NNF) in degraded or novel habitats. In highly urbanized Hong Kong and Singapore, their richness has grown to exceed the number of native species. They include fishes introduced for aquaculture and a growing variety imported for tropical aquaria. Species that have life-history adaptations with no analogues among their East Asian counterparts have become particularly successful. As climate-change 'winners', NNF will become more prevalent in a warmer world, leaving a distinctive Anthropocene fingerprint upon freshwater ecosystems. This article is part of the theme issue 'The biosphere in the Anthropocene.'