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Coral Reefs are Disappearing

Updated on May 16, 2017

In her 2009 book Sea Sick, Alanna Mitchell writes “The worldwide decay of coral reefs – caused by the pollution from land, too much fishing, nasty practices to capture wild fish for the aquarium trade, and waters that are too hot because of global climate change – has already started to take its toll.”

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Coral Reefs a Rich Source of Marine Life

The Coral Reef Alliance points out that “Although they cover only two-tenths of one percent of the ocean floor, these complex tropical ecosystems rival the rainforests in terms of biodiversity, supporting nearly a quarter of all marine species.”

Writing in The Independent Steve Connor says that coral reefs “provide food for about 500 million people around the world.”

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Carbon Dioxide Threatens Reefs

According to the Coral Reef Alliance, the burning of fossil fuels releases carbon dioxide and billions of tonnes have been absorbed by the oceans. This has changed the chemistry of sea water making it more acidic. As a result, coral and shell formations are impaired; when the shells stop forming the reef crumbles quickly.

Dr. Jacob Silverman of the Carnegie Institution of Science in Washington has studied this problem and has used a mathematical model to see what rising acidity will do to 9,000 coral reefs around the world.

He told a meeting of the American Association for the Advancement of Science in San Diego and quoted in The Telegraph that “A global map produced on the basis of these calculations shows that all coral reefs are expected to stop their growth and start to disintegrate when atmosphere CO2 reaches 560 parts per million – double its pre-industrial level – which is expected by the end of the 21st-century.”

The atmospheric concentration of CO2 as of April 2017 is 409 ppm; it passed the 400 ppm level in May 2013.

A wasteland of dead coral.
A wasteland of dead coral. | Source

Great Barrier Reef

Off the coast of Queensland, Australia, the Great Barrier Reef is, or more accurately, was one of the world’s great natural wonders. It stretches for 2,300 kilometres and is breathtakingly beautiful. But, the reef is in trouble.

Here’s a report from The New York Times (March 2017), “Huge sections of the Great Barrier Reef, stretching across hundreds of miles of its most pristine northern sector, were recently found to be dead, killed last year by overheated seawater.”

The tiny creatures, called polyps, that form corals are very sensitive to changes in temperature. A rise of one or two degrees Fahrenheit is enough to kill the animals in a process called bleaching. By a conservative estimate, the world’s ocean temperatures have risen 1.5 degrees Fahrenheit since the late 19th century. An additional jump caused by an El Niño effect, as happened in 2016, spells disaster for coral reefs.

The Great Barrier Reef is a huge tourism attraction bringing in billions of dollars of revenue a year and supporting about 70,000 jobs.

Coral Bombing Destroys Habitat and Fish

Among the reefs of the Philippines, Indonesia, Micronesia, and Africa, people are using dynamite to catch fish. Blast-fishers throw pop-bottle grenades into reef areas. The explosion kills everything nearby and the “fishers” retrieve the dead fish that float to the surface, mostly for local consumption. The explosion also rips apart the coral. The structures made by these living corals are very slow growing; some can take centuries to form.

According to Kate McClellan (Encyclopedia of the Earth) “The use of blast devices is economically efficient – a single bomb costs about 1-2 U.S. dollars to build, while the resulting catch is worth between 15 and 40 U.S. dollars.”

Blast fishing has been made illegal in the Philippines, Malaysia and other areas but it still goes on, because it’s difficult to police long coastlines.

Cyanide Fishing for Aquariums

Cyanide fishing first appeared in the Philippines in the early 1960s and, writes Christie Wilcox (Hakai Magazine, June 2016), it “is one of the most destructive techniques used for catching live fish …”

Divers use squeeze-bottles to squirt a solution of sodium cyanide into coral where reef fish hide. The idea is to temporarily stun the fish, net them, and put them into tanks for transport to aquariums for sale. A study has found that almost half the saltwater fish sold in pet stores in the U.S. are caught by cyanide fishing.

Unfortunately, the cyanide kills the coral.

Many other Threats to Coral

The Coral Reef Alliance lists many other activities that destroy coral reefs:

  • Sewage dumped untreated into oceans and fertilizer run off cause massive increases in algae, which blocks sunlight from coral reefs causing them to die;
  • Construction, mining, farming, and logging can all lead to erosion. Particles of soil and dust are carried into the ocean by rivers and can settle on coral reefs, smothering them;
  • Mangrove forests, which protect coral, are being destroyed to make way for shrimp farming and beach development;
  • Coral is sometimes taken for building materials and to make trinkets for tourists; and,
  • The increased ultraviolet radiation from the Sun that comes from thinning of the ozone layer around the planet may contribute to coral reef weakening.

Coral reef locations.
Coral reef locations. | Source

Coral Reefs Disappearing

With all of these impacts it’s not surprising that coral reefs are in trouble. The Coral Reef Alliance says that with 11 percent of reefs already destroyed “Scientists predict that another 32 percent may be lost in the next thirty years if human threats are not reduced.”

Dr. Silverman of the Carnegie Institution of Science says “… these ecosystems, which harbour the highest diversity of marine life in the oceans, may be severely reduced within less than 100 years.”

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Bonus Factoids

Defenders of Wildlife says “About one-third of all marine fish species live part of their lives on coral reefs.”

According to Conserve Energy Future “Scientists have discovered that many parts of a coral reef can be harvested to make medications to treat cancers and other illnesses.”

Coral reefs are places of incredible biodiversity second only to rainforests in the variety of species they host. A two-acre patch of coral can contain more species of fish than there are bird varieties in North America.


The red lionfish is a coral reef dweller you don't want to meet. Its poisonous sting is extremely painful though rarely fatal.
The red lionfish is a coral reef dweller you don't want to meet. Its poisonous sting is extremely painful though rarely fatal. | Source

Sources

  • “Coral Reefs in Danger of Being Destroyed.” Steve Connor, The Independent, February 24, 2010.
  • “AAAS: Coral Reefs Could Disappear by the End of the Century.” Richard Alleyne, The Telegraph, February 24, 2010.
  • “Large Sections of Australia’s Great Reef Are Now Dead, Scientists Find.” Damien Cave and Justin Gillis, New York Times, March 15, 2017.
  • “Coral Degradation Through Destructive Fishing Practices,” Kate McClellan, Encyclopedia of the Earth, August 24, 2008.
  • “Fishing With Cyanide.” Christie Wilcox, Hakai Magazine, June 30, 2016
  • Coral Reef Alliance.

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