Coral reefs: Why are they so important?

Coral reefs are essentially just big limestone structures built by thousands of tiny coral creatures called polyps. They're found in more than 100 countries, and just like pina coladas, they belong in tropical areas. But they're not looking too healthy. 

Increased ocean temperature caused by climate change is the main cause of coral bleaching events. That's when reefs expel the symbiotic algae responsible for their color. If that happens over longer periods, the corals can eventually die. 

The planet has already lost about half of its shallow water corals in the past three decades. And at the current rate, up to 90% of them will disappear by the middle of the century.

What are reefs good for?

Some 200 million people around the world depend on reefs to protect their coastal communities from storm surges and waves. Many of those people live in the US. 

Coral reefs act like low-crested breakwaters and absorb 97% of wave energy. This substantially reduces coastal flooding and erosion.  

According to the United States Geological Survey, reefs help avert $1.8 billion in damage each year in areas like Florida, Hawaii and Puerto Rico. And if those reefs lose just 1 meter in height, $5 billion in property and economic damage is at risk. 

With coastal flooding predicted to worsen this century, reefs will play an even more important role. But coastal defense is not the only thing reefs do for us.

What else reefs do

Coral reefs cover less than 0.5% of the earth's surface, but they are home to about 25% of all marine species. Kind of like the rainforests of the sea. 

With biodiversity, more is better. It provides planetary resilience, a vast resource of potential scientific discoveries, and is the result of millions of years of evolution. Biodiversity underpins a healthy planet and social well-being. 

Almost everything we know about coral reefs is based on those close to our shores, but most of them are distant, biodiverse hotspots in otherwise barren ocean basins, where they act as food bowls, rest stops, and even navigation waypoints for critters on the go. This diversity is a treasure of incalculable value.

Ignoring the intangible loss of heritage, allowing the destruction of these reefs is like burning the Great Library of Alexandria. We will never know what we've lost. 

Why does that matter?

A huge number of modern medicine's drugs are derived from natural sources. And so far, most of those have come from land organisms. 

But given 80% of life is under water, researchers are increasingly looking to marine organisms to satisfy the need for novel chemicals and enzymes to build the pharmaceuticals of tomorrow. Some estimates say the likelihood of discovering new drugs in the sea, particularly in coral reefs, is hundreds of times more likely than finding ones on land. 

The anticancer agent Ara-C, included on the World Health Organization's List of Essential Medicines, is found in sea sponges on a Caribbean reef. 

Ever heard of a sea hare? It's a name given to some gastropods that contain Dolastatin 10, which is being tested as a treatment for breast and liver cancers, tumors, and leukemia.

One promising molecule, eleutherobin, that is believed to slow cancer cell growth is found in a common species of soft coral. Scientists have been able to use its genetic code to figure out how they might soon be able to manufacture the chemical in large quantities. Another success story from nature's medicine cabinet is trabectedin, found in the sea squirt Ecteinascidia turbinata, and used in chemotherapy. 

Coral reefs provide habitat

Humans eat about 150 million tons of seafood a year and these fish have to breed somewhere. Reefs provide shelter and function as nursery grounds for some commercially important fish, such as grouper and snapper, as well as invertebrates like lobster.

Some studies put the value of coral reef fisheries at $6.8 billion a year globally. About one billion people source their food or income directly from reefs. In countries like the Maldives, they provide people with 77% of their dietary animal protein. If managed well, reefs can continue providing this important source of food. 

And if they're not managed well?

Potential food shortages could be the consequence. Especially when combined with failing crops from climate change. A study of reef damage in Kenya revealed drastic declines in key fish catches after a combination of factors in 1998 warmed the ocean by between 1-2 degrees Celsius.  

That's not to mention the possibility of increased mass migration, as people try and avoid famine and flooding.

There is a myriad of ways to protect reefs — local restoration efforts by transplanting coral, the establishment of marine protection areas which work like national parks, and stopping run-off from agricultural and effluence.

But with climate change posing the biggest singular threat to the future of coral reefs, in the long term, reducing emissions will give them their best shot at survival.

Edited by: Tamsin Walker and Jennifer Collins