Freshwater facts & figures
- Around 10,000 of the world’s 25,000 known fish species live in fresh water. An average of 300 new freshwater fish species are discovered every year1.
- Wetlands around the world provide goods and services to people worth an estimated US$70 billion a year2.
- Freshwater ecosystems have a higher concentration of species relative to their area than land or sea3.
- Globally, water pollution is increasing4. In developing countries, an estimated 90% of waste water is discharged directly into rivers and streams without treatment5.
- Fragmentation of river systems due to dams is the single greatest threat to freshwater ecosystems’ health. There are an estimated 800,000 dams worldwide, including around 45,000 large dams (over 15 metres high)6 and 1,000 mega-dams over 100 metres high7. Over 60% of the world’s 227 largest rivers have been fragmented by dams, diversions and canals8. An estimated 60 to 80 million people have been displaced by dams6 and nearly 500 million people have had their lives and livelihoods negatively affected9.
- People use 54% of the planet's “blue water” (water that flows through rivers, lakes, and groundwater). Estimates suggest that this may increase to 70% by 202510.
- 2.3 billion people live in river basins which are under water stress, where less than 1,700 cubic metres of water is available for each person per year. If current consumption patterns continue, at least 3.5 billion people will live in water-stressed river basins in 2025 - half the world’s projected population11.
- Our Freshwater Living Planet Index (which tracks changes in populations of 714 species of fish, birds, mammals, reptiles and amphibians found in temperate and tropical lakes, rivers and wetlands) showed populations of freshwater species fell by 35% between 1970 and 2007 - a larger decline than in marine and land ecosystems. In tropical regions the decline was almost 70%12.
- Climate change is predicted to have a whole range of impacts on water resources. Variation in temperature and rainfall may affect water availability, increase the frequency and severity of floods and droughts, and disrupt ecosystems that maintain water quality13.
- Over the last 50 years, the frequency of severe flooding and the damage it causes have increased, in part due to the degradation of freshwater ecosystems14.
- In parts of the United States, Europe, Australia and New Zealand, over half of wetlands were destroyed in the 20th century, and many more were degraded across the rest of the world15.
1. Groombridge, B and Jenkins, M, 1998. Freshwater biodiversity: a preliminary global assessment, WCMC, Cambridge.
2. WWF, 2004. Economic value of wetlands.
3. Millennium Ecosystem Assessment, 2005. Ecosystems and human well-being: wetlands and water synthesis. Island Press, Washington, DC.
4. UN WWAP, 2009. The United Nations Development Report 3: water in a changing world. UNESCO, Paris: UNESCO.
5. Johnson, N, Revenga, C and Echeverria, J, 2001. Managing water for people and nature, Science, 292.
6. World Commission on Dams, 2000. Dams and development: a new framework for decision-making. The report of the World Commission on Dams. Earthscan, London.
7. WWF, 2001. Dams and development: WWF's response to the report of the World Commission on Dams.
8. WWF, 2004. Rivers at risk: dams and the future of freshwater ecosystems.
9. Richter, BD, Postel, S, Revenga, C, Scudder, T, Lehner, B, Churchill, A, and Chow, M, 2010. Lost in development’s shadow: The downstream human consequences of dams. Water Alternatives, 3(2): 14-42.
10. Postel, SL, Daily, GC and Ehrlich, P, 1996. Human appropriation of renewable freshwater, Science, 192: 785-788.
11. Revenga, C, Brunner, J, Henninger, N, Kassem, K and Payne, R, 2000. Pilot Analysis of Global Ecosystems: Freshwater Ecosystems Technical Report. World Resources Institute, Washington, DC.
12. WWF, 2010. Living Planet Report 2010: Biodiversity, Biocapacity and Development.
13. IPCC, 2007. Climate Change 2007: Climate Change Impacts, Adaptation and Vulnerability, Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge.
14. Millennium Ecosystem Assessment, 2005. Ecosystems and human well-being: synthesis. Island Press, Washington, DC.