<p>Photo: A heat-damaged reef in the Indian Ocean offers poor habitat for fish</p>

A school of fish swims past heat-damaged coral in Maldives. When stressed by temperatures changes, pollution, and other factors, coral will evict the algae that gives them their spectacular colors. This process is called bleaching.

Photograph by Peter Essick

Freshwater ecosystems are essential for human survival, providing the majority of people's drinking water. The ecosystems are home to more than 40 percent of the world's fish species. Despite their value and importance, many lakes, rivers, and wetlands around the world are being severely damaged by human activities and are declining at a much faster rate than terrestrial ecosystems.

More than 20 percent of the 10,000 known freshwater fish species have become extinct or imperiled in recent decades. Watersheds, which catch precipitation and channel it to streams and lakes, are highly vulnerable to pollution. Programs to protect freshwater habitats include planning, stewardship, education, and regulation.


  • The creation of dams and water-diversion systems blocks migration routes for fish and disrupts habitats.
  • Water withdrawal for human use shrinks and degrades habitats.
  • Runoff from agricultural and urban areas hurts water quality.
  • Draining of wetlands for development depletes habitats.
  • Overexploitation and pollution threaten groundwater supplies.
  • Invasion of exotic species can harm native animals and plants.
  • Global warming may lead to devastating floods and droughts.


  • Restrict the construction of dams.
  • Provide incentives for farming business to reduce the use of pesticides.
  • Establish protected wetlands areas.
  • Regulate water withdrawal for human use.


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