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Freshwater facts & figures

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Facts and figures

  • Approximately 10,000 of the world's 25,000 known fish species are freshwater animals, and an average of 300 new freshwater fish species are described every year1. Wetlands around the world provide goods and services to people worth an estimated US$70 billion a year2.
  • In developing countries, an estimated 90% of wastewater is discharged directly into rivers and streams without treatment3.
  • Fragmentation of river systems due to dams is the single greatest threat to the maintenance of ecosystem integrity. The total number of dams worldwide is estimated at 800,000, including some 1,000 mega-dams over 100m high4.
  • Humans currently expropriate some 54% of the planet's 'blue water' (water that flows through rivers, lakes, groundwater etc). Estimates suggest that this may increase to 70% by 20255.
  • Approximately 2.3 billion people live in river basins under water stress, where annual per capita water availability is below 1,700 cubic metres. If current consumption patterns continue, at least 3.5 billion people will live in water-stressed river basins in 2025 – around 48% of the world's projected population.
  • WWF's Living Planet Index (2007) shows that the Freshwater Species Population Index (which comprises populations of 195 species of birds, mammals, reptiles, amphibians, and fish from lakes, rivers, and wetland ecosystems) fell 29% between 1970 and 2003.
  • Climate change is predicted to have a whole range of impacts on water resources6. Water resources are becoming even more vulnerable, and the likelihood is that flooding will become a more significant risk in many temperate and humid regions, which is likely to affect infrastructures and safety.

Footnotes

1. Groombridge, B and Jenkins, M, 1998. Freshwater biodiversity: a preliminary global assessment, WCMC, Cambridge.
2. Economic value of wetlands, WWF 2004.
3. Johnson, N, Revenga, C and Echeverria, J, 2001. Managing water for people and nature, Science, 292.
4. WWF, 2001. Dams and development: WWF's response to the report of the World Commission on Dams.
5. Postel, SL, Daily, GC and Ehrlich, P, 1996. Human appropriation of renewable freshwater, Science, 192: 785-788.
6. van Deursen, 2000.