Freshwater megafauna diversity: Patterns,status and threats |
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| Authors: | Fengzhi He Vanessa Bremerich Christiane Zarfl Jonas Geldmann Simone D Langhans Jonathan N W David William Darwall Klement Tockner Sonja C Jähnig |
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| Institution: | 1. Leibniz‐Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany;2. Institute of Biology, Freie Universit?t Berlin, Berlin, Germany;3. School of Geography, Queen Mary University of London, London, UK;4. Center for Applied Geosciences, Eberhard Karls Universit?t Tübingen, Tübingen, Germany;5. Department of Zoology, Conservation Science Group, University of Cambridge, Cambridge, UK;6. School of Geography and the Environment, University of Oxford, Oxford, UK;7. Freshwater Biodiversity Unit, IUCN Global Species Programme, Cambridge, UK;8. Austrian Science Fund (FWF), Vienna, Austria |
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| Abstract: | Aim Freshwater megafauna remain underrepresented in research and conservation, despite a disproportionately high risk of extinction due to multiple human threats. Therefore, our aims are threefold; (i) identify global patterns of freshwater megafauna richness and endemism, (ii) assess the conservation status of freshwater megafauna and (iii) demonstrate spatial and temporal patterns of human pressure throughout their distribution ranges. Methods We identified 207 extant freshwater megafauna species, based on a 30 kg weight threshold, and mapped their distributions using HydroBASINS subcatchments (level 8). Information on conservation status and population trends for each species was extracted from the IUCN Red List website. We investigated human impacts on freshwater megafauna in space and time by examining spatial congruence between their distributions and human pressures, described by the Incident Biodiversity Threat Index and Temporal Human Pressure Index. Results Freshwater megafauna occur in 76% of the world’s main river basins (level 3 HydroBASINS), with species richness peaking in the Amazon, Congo, Orinoco, Mekong and Ganges‐Brahmaputra basins. Freshwater megafauna are more threatened than their smaller counterparts within the specific taxonomic groups (i.e., fishes, mammals, reptiles and amphibians). Out of the 93 freshwater megafauna species with known population trends, 71% are in decline. Meanwhile, IUCN Red List assessments reported insufficient or outdated data for 43% of all freshwater megafauna species. Since the early 1990s, human pressure has increased throughout 63% of their distribution ranges, with particularly intense impacts occurring in the Mekong and Ganges‐Brahmaputra basins. Main conclusions Freshwater megafauna species are threatened globally, with intense and increasing human pressures occurring in many of their biodiversity hotspots. We call for research and conservation actions for freshwater megafauna, as they are highly sensitive to present and future pressures including a massive boom in hydropower dam construction in their biodiversity hotspots. |
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| Keywords: | conservation flagship species freshwater biodiversity hotspot human impact size umbrella species |
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