Several studies of freshwater fishes have examined the effects of climate change on individual species or in specific countries, many suggesting that the group may be especially vulnerable considering changes in hydrological regimes.
Taking a holistic approach, this study provides a global assessment of predicted climate-induced changes to the diversity and richness of watersheds around the world, modelling the current and future distributions of more than 16,000 freshwater fish species based on GBIF-mediated occurrences.
Under two different climate scenarios, the study predicts the complete disappearance of distributional areas of about half of all freshwater fish species by the year 2070, a decline more pronounced in tropical river basins and particularly high in southeast Asia, mainly affecting species with smaller body size.
On average, across all watersheds, approximately 20 per cent of species are predicted to be lost by 2050. The most important climatic predictors observed were annual precipitation and isothermality (the relationship between mean daily temperature and annual temperature range), such that species richness declined at higher rates in watersheds with high annual rainfall and temperature seasonality. In addition to a reduction in number of species, the predicted richness decline will also lead to a significant reduction in phylogenetic and functional diversity.