COS 206-2 - Modelling threats to freshwater ecosystems to optimize conservation efforts

Abstract: Freshwater ecosystems are one of the most diverse habitats on Earth, accounting for approximately 30% of vertebrate diversity while occupying ~1% of land surface. These habitats are strongly impacted by human activities, including physical alteration, species invasions, pollution, and climate change, leading to steeper declines in freshwater species than terrestrial or marine counterparts. The International Union for Conservation of Nature (IUCN) Red List cites 27% of freshwater vertebrates as being at risk of extinction. To prioritize conservation efforts to safeguard freshwater species, we are unifying data on species of all freshwater vertebrates and then intersecting biodiversity patterns with threat maps. This approach parallels two decades of work to identify ‘hotspots’ where threats are acute and both species richness and endemicity are high, but we explore the reverse approach. By seeking "coldspots" where high richness of range-limited taxa occurs in areas that are not currently threatened, we offer an alternative model for global-scale prioritization of regions for conservation interventions. The sites may still be susceptible to future threats, but acting now could enable lower-cost pathways to establishing reserves or applying other conservation tools. Recalculating these priorities at a continental scale can identify hotspots and coldspots within each major faunal zone to provide actionable conservation outcomes. We find that human development poses a significant, increasing threat to freshwaters in vast areas, especially in tropical and subtropical regions. Especially, our research underscores the urgency of conservation efforts in the Amazon and Gulf of Guinea basins, as well as northern areas of Oceania and New Guinea, where the regionally-highly freshwater diversity will face growing threats. In the context of the UN's call for 30% of the world to be under protection and management regimes by 2030, it is essential to account for the special characteristics of freshwater ecosystems, especially in regions where declining vertebrate biodiversity jeopardizes both the functioning of freshwater ecosystems and their contributions to human well-being.