Freshwater ecosystems are highly biodiverse¹ and important for livelihoods and economic development², but are under substantial stress³. To date, comprehensive global assessments of extinction risk have not included any speciose groups primarily living in freshwaters. Consequently, data from predominantly terrestrial tetrapods^4,5 are used to guide environmental policy⁶ and conservation prioritization⁷, whereas recent proposals for target setting in freshwaters use abiotic factors^8–13. However, there is evidence^14–17 that such data are insufficient to represent the needs of freshwater species and achieve biodiversity goals^18,19. Here we present the results of a multi-taxon global freshwater fauna assessment for The IUCN Red List of Threatened Species covering 23,496 decapod crustaceans, fishes and odonates, finding that one-quarter are threatened with extinction. Prevalent threats include pollution, dams and water extraction, agriculture and invasive species, with overharvesting also driving extinctions. We also examined the degree of surrogacy of both threatened tetrapods and freshwater abiotic factors (water stress and nitrogen) for threatened freshwater species. Threatened tetrapods are good surrogates when prioritizing sites to maximize rarity-weighted richness, but poorer when prioritizing based on the most range-restricted species. However, they are much better surrogates than abiotic factors, which perform worse than random. Thus, although global priority regions identified for tetrapod conservation are broadly reflective of those for freshwater faunas, given differences in key threats and habitats, meeting the needs of tetrapods cannot be assumed sufficient to conserve freshwater species at local scales.

Ion-specific standards are needed to protect biodiversity

Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global consultation, we identify 15 pressing priority needs, grouped into five research areas, in an effort to support informed stewardship of freshwater biodiversity. The proposed agenda aims to advance freshwater biodiversity research globally as a critical step in improving coordinated actions towards its sustainable management and conservation.

This review is part of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) report on Europe and Central Asia (ECA) and provides a critical assessment of issues facing decision-makers, including freshwater biodiversity and ecosystem trends as well as drivers of change. Freshwater systems are well established as the most threatened ecosystem type in the ECA region, with the quantity and quality of habitats and abundance of many species rapidly declining. Only about half (53%) of the EU's rivers and lakes achieved good ecological status in 2015 (as defined by the Water Framework Directive in terms of the quality of the biological community), and many lakes, ponds, and streams are disappearing as a consequence of agricultural intensification and inefficient irrigation and urbanisation, combined with climate change. The situation regarding freshwater biodiversity remains highly critical in ECA as many species remain threatened with extinction, including >50% of known species for some groups (e.g., molluscs, amphibians). Drivers of ECA freshwater taxa include the destruction or modification of their habitat, including water abstraction, which affects ∼89% of all amphibian threatened species and ∼26% of threatened freshwater invertebrate species. Of particular concern is the lack of data for freshwater invertebrates. Current status is available for only a minority of species, and the impact of alien invasive species is often unknown, especially in Central Asia. Based on current freshwater biodiversity trends, it is highly unlikely that ECA will achieve either the respective Aichi biodiversity targets by 2020 (i.e., targets 2 to 4, 6 to 12, and 14) or Target 1 of the Biodiversity Strategy.

This review of trends in inland saline lakes of Europe and Central Asia is based on the relevant section of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) Regional Assessment Report for Europe and Central Asia (ECA). We assessed the present status of ECA saline lakes and the effects of direct drivers (climate change, land use, pollution, resource exploitation, invasive species) on ecosystem health and biodiversity. We also assessed past, current and future trends using habitat area and degradation, species richness, and endangered species as indicators. No uniform scenario is applicable to saline lakes in the region. The desiccation of the Aral Sea is caused mainly by land use change and water extraction. In the Caspian Sea, river modifications, water pollution, overfishing and poaching, and species invasions have led to a decrease in species richness and have threatened endemic species. Although trends for smaller saline lakes vary, our analysis demonstrates that land use change, over-exploitation, and pollution are more important direct drivers of ecosystem health and biodiversity than climate change. The establishment of baseline biodiversity values for saline lakes is, however, complicated because biodiversity and the food-web structure are variable and depend strongly on salinity. Thus, there is a need to classify the ecological quality, biodiversity and ecosystem services of saline lakes along a salinity gradient. The improvement of water management and reuse of water, conservation measures, and introduction of climate-smart agriculture are basic conditions for the sustainable use of saline lakes in the region.