Coral reefs | WWF

Coral reefs are home to 25% of all marine life on the planet. In fact the variety of life supported by coral reefs rivals that of the tropical forests of the Amazon or New Guinea. But without urgent action to address climate change, pollution, overfishing and other threats these beautiful and life-sustaining organisms could disappear.

Why corals bleach


Can coral survive a bleaching event? If the stress-caused bleaching is not severe, coral have been known to recover. If the algae loss is prolonged and the stress continues, coral eventually dies.

Coral reef, Fiji. rel= © WWF / Cat HOLLOWAY

Coral reefs: home to 25% of all marine life

The variety of life supported by coral reefs rivals that of the tropical forests of the Amazon or New Guinea.
The total area of the world's coral reefs amounts to less than one quarter of 1% of the entire marine environment.

Yet some estimates put the total diversity of life found in, on, and around all coral reefs at up to 2 million species. All up, reefs are home to 25% of all marine life, and form the nurseries for about a quarter of the ocean's fish -  including commercially important species that could end up on your dinner plate any night of the week.

This biodiversity translates directly into food security, income, and a multitude of other benefits to people. For example, although scientists have only just begun to understand how reefs can contribute to medicine, already coral reef organisms are being used in treatments for diseases like cancer and HIV.

For many coastal areas, coral reefs also provide an important barrier against the worst ravages of storms, hurricanes, and typhoons.

As thousands of communities across the world will tell you, coral reefs are essential not only to ocean health, but also to human health and well-being.

Priority species

Corals are a WWF priority species. WWF treats priority species as one of the most ecologically, economically and/or culturally important species on our planet. And so we are working to ensure such species can live and thrive in their natural habitats.

    © WWF / Songpol Tippayawong
New Coral Reef discovered in Thailand, Feb 2006
© WWF / Songpol Tippayawong

Where can I find coral reefs?

Coral reefs can be found around the world and even in some places that you would not expect. In recent years scientists have discovered cold water coral reefs off the coast of Norway and deep underwater in the Mediterranean Sea. WWF priority regions with extensive coral reefs are: the Coral Triangle and the Mesoamerican Reef.
    © WWF / Anthony B. RATH
The Mesoamerican Reef – a priority ecoregion for WWF – covers a large territory of water, from the Bay Islands in the north of Honduras to the Yucatan Peninsula in Mexico, including the coasts of Guatemala and Belize. Laughing Bird Caye, Belize.
© WWF / Anthony B. RATH

Map showing distribution of coldwater and tropical coral reefs. rel= © Hugo Ahlenius, UNEP/GRID-Arendal

What are the main threats to coral reefs?

Coral reefs have survived tens of thousands of years of natural change, but many of them may not be able to survive the havoc wrought by humankind.

Roughly one-quarter of coral reefs worldwide are already considered damaged beyond repair, with another two-thirds under serious threat.

Major threats to coral reefs and their habitats include:
  • Climate change: Corals cannot survive if the water temperature is too high. Global warming has already led to increased levels of coral bleaching, and this is predicted to increase in frequency and severity in the coming decades. Such bleaching events may be the final nail in the coffin for already stressed coral reefs and reef ecosystems.
  • Destructive fishing practices: These include cyanide fishing, blast or dynamite fishing, bottom trawling, and muro-ami (banging on the reef with sticks). Bottom-trawling is one of the greatest threats to cold-water coral reefs.
  • Overfishing: This affects the ecological balance of coral reef communities, warping the food chain and causing effects far beyond the directly overfished population.
  • Careless tourism: Careless boating, diving, snorkeling, and fishing happens around the world, with people touching reefs, stirring up sediment, collecting coral, and dropping anchors on reefs. Some tourist resorts and infrastructure have been built directly on top of reefs, and some resorts empty their sewage or other wastes directly into water surrounding coral reefs.
  • Pollution: Urban and industrial waste, sewage, agrochemicals, and oil pollution are poisoning reefs. These toxins are dumped directly into the ocean or carried by river systems from sources upstream. Some pollutants, such as sewage and runoff from farming, increase the level of nitrogen in seawater, causing an overgrowth of algae, which 'smothers' reefs by cutting off their sunlight.
  • Sedimentation: Erosion caused by construction (both along coasts and inland), mining, logging, and farming is leading to increased sediment in rivers. This ends up in the ocean, where it can 'smother' corals by depriving them of the light needed to survive. The destruction of mangrove forests, which normally trap large amounts of sediment, is exacerbating the problem.
  • Coral mining: Live coral is removed from reefs for use as bricks, road-fill, or cement for new buildings. Corals are also sold as souvenirs to tourists and to exporters who don't know or don't care about the longer term damage done, and harvested for the live rock trade.
Bleached Acropora coral head, Papua New Guinea 
    © Jürgen Freund / WWF
Bleached Acropora coral head, Papua New Guinea.
© Jürgen Freund / WWF

What WWF is doing

WWF works to protect areas rich in corals.

It has been exploring and protecting the Coral Triangle for some 20 years. It helps create policies to ensure responsible environmental management of the area, raise awareness, and promote the sharing of skills for better stewardship of the Coral Triangle's amazing marine world.

We work on major global policy issues facing reefs, particularly climate change, and also with communities, governments and partners around the world to reduce the threats to reefs including in the following regions: For more information on the global approach to reefs and to recent analyses of their important roles in Melanesia and the Western Indian Ocean, please see reports at:
    © WWF / Jürgen Freund
WWF researcher monitoring a coral reef in the Sulu Sea.
© WWF / Jürgen Freund

How you can help

  • Vote Earth by taking part in Earth Hour! As the biggest threat to coral reefs worldwide is climate change, we need to send a message to our leaders that warming must be limited to under 2 degrees Celsius.
  • Spread the word! Click on the button to share this information with others via email or your favourite social networking service.

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Did you know?

  • The Great Barier Reef is the largest living thing on the planet.
  •  A quarter of the world's fish rely on coral reefs as nurseries.
  • The zooxanthellae algae which live symbiotically inside the coral polyp give the corals their amazing colours.
  • Properly managed coral reefs can yield an average 15 tonnes of fish and other seafood per sq km per year