The corals that make up reefs around the world are living animals that provide marine species with food, fertile grounds for reproduction, and a safe haven from predators.

A Living Animal
Despite their appearances, corals are neither rocks nor plants — corals are living animals. There are two types of corals — hard corals and soft corals. Hard corals resemble rocks, boulders, or tree trunks. Soft corals can look like tree branches, whips, or fans. Over time, as some of the animals die, their hard skeletons accumulate below the living animals to form a permanent structure called a coral reef.

Home to Ocean Life
Coral reefs support more than 25% of all known marine species. As one of the most complex ecosystems on the planet, coral reefs are home to over 4,000 different species of fish, 7,000 species of corals, and thousands of other plants and animals. So much marine life relies on corals because they provide sustenance as well as a safe, protected place for reproduction, for young fish to grow, and for shielding from predators.

Valuable to Human Life
Scientists estimate that coral reefs provide an economic benefit of $375 billion each year to millions of people around the world. Studies show that on average, countries with coral reef industries derive more than half of their gross national product from them. Coral reefs play a vital role in human health. By providing habitat to reef fishes, coral reefs are a critical source of protein for millions of people around the world. In addition, corals have many uses in medicine. The most famous pharmaceuticals using chemicals from corals are AZT and Taxol, which are used to treat HIV infections and cancer respectively. Researchers continue to look for corals to provide treatments for other diseases.

Coral reefs also can protect coastal communities from natural disasters. A study of the 2004 tsunami in Asia showed that the presence of healthy coral could reduce the tsunami’s reach by 50%. In parts of Sri Lanka that had a history of heavy coral mining, the tsunami had higher waves, reached further inland, and resulted in more severe damage. By contrast, nearby areas with healthy reefs showed significantly reduced damage.

But Corals Are In Trouble

Despite their valuable contributions to society, corals are under assault on numerous fronts. The key threats to their survival are listed below:

Excess carbon dioxide emissions are changing the earth’s climate. The effects of this change are warming the earth, increasing the ocean temperature, and putting tropical corals in grave danger. When the water temperature rises too high, corals will reject the symbiotic plants living inside their tissues. As a result, corals lose up to 80% of their source of energy, lose their pigment, and turn white. If the water is too hot for too long, the bleached corals will eventually die. Another result of excess carbon dioxide in the atmosphere is an increase in the ocean’s acidity. This change in the chemistry of the ocean is causing corals to become more fragile and more vulnerable to storms and disturbance.

Direct removal of corals from the sea for use in jewelry, décor, and home aquariums has resulted in a downward spiral in coral populations. Precious red and pink corals, in particular, have had symbolic and cultural importance for thousands of years, and their rise in popularity as a fashion item is now threatening their survival. Corals are also sometimes removed from the ocean through mining to produce lime and materials for construction or paving roads. Corals grow so slowly that it can take decades for them to recover, if at all.

Overfishing and destructive fishing techniques are another leading cause of coral reef degradation. Many coral reef fish act as gardeners that regularly “mow” the plants and algae that grow on top of the reef. When reef fish are overfished, the plants will take over and eventually smother the corals. There are also several fishing methods that directly destroy corals:

Blast Fishing —The shock waves from a small amount of dynamite or other explosives set off underwater will kill fish and make them float on the surface of the water. This makes it very easy for a fisher to collect the catch, but the explosion can kill the surrounding coral reefs.

Bottom Trawling —Fishing gear designed to catch fish in deep places, such as bottom trawls or rockhoppers, drag large, heavy nets along the ocean floor. This gear destroys everything in its path, including corals, which get caught in the nets and reduced to rubble.

Cyanide Fishing —Another destructive fishing technique is used by divers who spray cyanide into coral crevices to stun fish and then capture them. Over time, the accumulation of cyanide damages the coral reef.

Pollution, such as oil spills, oil leaks from motorboats, untreated sewage, and runoff from fertilizers and pesticides from agricultural and other activities, all have long-term negative impacts on corals.