If you’ve spent any time snorkeling or scuba diving in places like Australia, the Galápagos Islands, or Polynesia, you don’t need me to tell you that exploring the underwater world can be an extraordinary adventure. And if you follow environmental news, you also don’t need me to tell you about the dangers climate change pose to the future of our planet’s marine ecosystems. So instead, here are 25 fascinating facts about coral reefs that you might not know, from general info and the benefits of coral reef systems to a few of the world’s most impressive sites. (More of a visual person? Check out our infographic!)
General Facts About Coral Reefs
1. Corals come in a wide array of shapes, sizes, and colors. Some are thought to resemble deer antlers, trees, giant fans, brains, and honeycomb.
2. Although many corals may look like plants, they’re actually animals; they are most closely related to jellyfish and anemones.
3. There are three different types of coral reef formations—barrier reefs, coral atolls, and fringing reefs. Barrier reefs help to protect lagoons and other types of shallow water, coral atolls (which are often mistaken for islands) are made from volcanic remains, and fringing reefs are found right along the coastline.
4. Coral reefs grow very slowly, at an average rate of just two centimeters per year.
5. Coral reefs only grow at a maximum depth of around 150 feet. This is because their biomes must maintain a temperature of 70 to 85º Fahrenheit. (Shallow water is more easily warmed by the sun.)
6. Strangely, most coral reefs seem to grow on the eastern side of land masses, where the temperature is believed to be warmer than the western side.
7. If you find a broken piece of coral on the beach, you can see its hard shell, which is actually an animal called a polyp. It is the cluster of these polyps growing together that gives coral reefs their shape.
8. Some coral reefs are more biodiverse than others. The array of marine species living within the coral reef’s biome depends on the location’s latitude and the direction of the water.
9. Coral reefs seem to grow best where there are stronger currents and wave patterns. Scientists believe that this is because stronger currents and waves deliver more food for the marine ecosystem.
10. The algae that typically grows on and around a coral reef isn’t a plant, but a living creature. There are many different kinds of algae, from microscopic varieties to ones with leaf-like appendages that can grow several feet long.
The Benefits of Coral Reefs
11. Scientists have discovered that many parts of a coral reef can be harvested to make medications. According to the National Oceanic & Atmospheric Administration, coral reefs are emerging as the medicine cabinets of the 21st century: “Coral reef plants and animals are important sources of new medicines being developed to treat cancer, arthritis, human bacterial infections, Alzheimer’s disease, heart disease, viruses, and other diseases."
12. Coral reefs are among the most biodiverse ecosystems on the planet. There are often more types of fish living in a two-acre area of healthy coral reef than there are species of birds in all of North America!
13. Coral reefs help to improve the quality of the surrounding water. They do this by filtering out things floating in the ocean, which leads to cleaner water.
14. Coral reefs help stabilize the sea bed, helping seagrass, seaweed, and other marine plants to survive. These plants lessen the impact of storms and help prevent the ocean bed from being washed out. They also provide food and protection for a broad variety of marine animals. Fish, manatees, dugongs, and countless other species feed and raise their offspring there.
15. In addition to protecting shorelines, coral reefs are immensely valuable to the fishing and tourism industries. According to the World Resources Institute, the destruction of one kilometer of coral reef equals a loss of between $137,000 to $1,200,000 over a 25-year period. And yet, they estimate some 60% of the world's coral reefs are currently threatened by human activity.
Facts About Coral Reefs Around the World
16. Australia’s Great Barrier Reef is the largest reef system in the world, and can be seen from outer space. Encompassing a 133,000-square mile area, it’s comprised of more than 2,900 individual reefs and 1,050 islands, which stretch out over 1,400 miles long.
17. Stretching over 550 miles from Cancun to Honduras, the Mesoamerican Barrier Reef is the world’s second largest coral reef system, attracting some 150,000 people to Mexico each year.
18. Located in the Philippines, Tubbataha Reefs Natural Park was declared a UNESCO World Heritage Site in 1993 due to its pristine coral reef system. Encompassing 97,030 hectares, the park’s two coral atolls are home to 600 species of fish, 360 species of coral, 11 species of sharks, 13 species of dolphins and whales, birds, plus hawksbill and green sea turtles.
19. Located between the Sahara and Arabian deserts, the Red Sea Coral Reef is noteworthy for its ability to withstand extreme temperature changes. Measuring 1,200 miles long, the reef is home to 300 hard coral species and about 1,200 fish, of which 10% are endemic to the area.
20. The Belize Barrier Reef, which was named a UNESCO World Heritage Site in 1996, stretches 190 miles along the country’s coastline. It is home to 70 hard coral species, 35 soft coral species, 500 species of fish, and hundreds of invertebrates.
Facts About Coral Reefs & Climate Change
21. Oceans are great at absorbing much of the dangerous carbon dioxide that enters the Earth’s atmosphere. Unfortunately, it makes the water increasingly acidic. This acidification prevents corals from absorbing the calcium carbonate they require in order to maintain their skeletons, and the stone-like skeletons that support them.
22. Coral reef systems are naturally colorful because of the algae that is usually present. If you see a coral reef that appears white—a process known as coral bleaching—it was most likely the result of warmer water temperatures caused by climate change.
23. The first widespread incident of coral bleaching happened in 1998, when an estimated 16% of corals died. But the worst incident on record occurred in 2015-2016, when an extended El Niño event warmed Pacific waters near the equator.
24. Recent studies suggest the planet has lost approximately half of its coral reefs in the last 30 years, and could lose more than 90% by the year 2050 if drastic changes are not made.
25. Marine scientists from The Nature Conservancy, 50 Reefs, and other NGOs are working diligently to fight climate change, protect the coral reefs we have left, and come up with innovative solutions. Even Ruth Gates, director of the Hawaii Institute of Marine Biology, is currently trying to breed and train new corals to better withstand rising ocean temperatures.
Bret Love is a journalist/editor with 23 years of print and online experience, whose clients have ranged from the Atlanta Journal-Constitution and American Airlines to National Geographic and Yahoo Travel. Along with his wife, photographer/videographer Mary Gabbett, he is the co-founder of ecotourism/conservation website Green Global Travel and Green Travel Media.