Photo: Great egret catching fish

A large fish proves more than a mouthful for a hungry great egret, which lost its prize soon after this shot was snapped. This big bird may be seen across much of the globe but is nearly always found near water where food is plentiful.

Photograph by Andy Nguyen, My Shot

Wetlands, rivers, lakes, and coastal estuaries are all aquatic ecosystems—critical elements of Earth’s dynamic processes and essential to human economies and health.

Wetlands connect land and water, serving as natural filters, reducing pollution, controlling floods, and acting as nurseries for many aquatic species. Rivers, lakes, and estuaries serve as important transportation, recreation, and wildlife hubs.

Learning more about the ecosystems within your watershed—all the water in your region that drains to the same point—can help you better understand how everything is connected and what is at stake with freshwater overuse, pollution, and drought.

Fast Facts

  • Global extinction rates for freshwater species are four to six times higher than those for terrestrial or marine species.
  • Forty percent of all fish species in North America are at risk of extinction.
  • In the U.S., 69 percent of freshwater mussel species, which help to filter water, are at risk of extinction.


Did You Know?

Freshwater ecosystems cover less than one percent of Earth’s surface, but are home to 35 percent of all vertebrate species.

More About Aquatic Ecosystems

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    Saving Our Fish

    Learn ways to save aquatic species, and the freshwater resources that support them, and us.

  • Photo: finger-length Ouachita madtom

    Imperiled Freshwater Species

    Freshwater fish are dying, but scientists have a rescue plan. Read more in National Geographic's freshwater issue.

  • <p>Photo: Zeb Hogan holding a large fish</p>

    Megafishes Project

    The Megafishes Project represents the first worldwide attempt to document and protect the planet's freshwater giants, which are disappearing at an alarming rate.

  • <p>Photo: A small frog</p>

    Vanishing Amphibians

    It's a race against time as scientists try to figure out how to save these keystone species before their populations shrivel.

Help Save the Colorado River

You can help restore freshwater ecosystems by pledging to cut your water footprint. For every pledge, Change the Course will restore 1,000 gallons back to the Colorado River.

Freshwater Advocates

  • Picture of Peter McBride in Kenya

    Freshwater Hero: Pete McBride

    Pete is a photographer and visual storyteller with an emphasis on freshwater conservation.

  • sandra new headshot.jpg

    Sandra Postel

    Sandra is a leading authority on international freshwater issues and is spearheading our global freshwater efforts.

  • Photo: Osvel Hinojosa Huerta

    Osvel Hinojosa Huerta

    For more than 15 years, Osvel Hinojosa Huerta has been resurrecting Mexico's Colorado River Delta wetlands.

For More Inspiration »

Change the Course Infographic


Check out this infographic and learn how you can conserve water and save the Colorado River, as well as other freshwater ecosystems.

Share it with your friends!

Water Currents, by Sandra Postel and Others

More Posts »

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