What good are coral reefs? They protect around 200 million people who live in coastal areas

Diver near coral reef
© Tim Calver for The Nature Conservancy

On top of being important biodiversity hotspots, they also help those of us who don't live underwater. Here's how...

One of the very bad things about global warming is that it puts significant pressure on coral reefs, the incredibly productive biodiversity hotspots where countless species live and mingle. This has a direct impact on the health of oceanic ecosystems, but it could also have an impact on coastal populations. Indeed, global warming doesn't just attack corals through ocean acidification and more elevated temperatures, it also causes stronger storms (warm water is hurricane fuel) against which coral reefs are an excellent protection. It's a double-whammy...

So how do coral reefs help protect coastal populations?

Coral Reefs infographicPew Charitable Trust/Promo image

It's simple. As you can see in the graphic above, open water waves hit the reef as they move in the direction of the coast. When they hit the reef, they crest and dissipate a lot of their energy. Researchers found that the reef crest, or shallowest part of the reef where the waves break first, dissipates 86% of wave energy on its own. By the time the waves reach the coast, 97% of the energy was dissipated on average, and the height of the wave was down by 84%. That's a huge difference, especially when you need it most (storms, tsunamis).

On this aerial photo, you can see waves cresting over a reef, losing a lot of their energy:

Waves breaking on the Great Mesoamerican Reef. Mike Beck for TNC© Waves breaking on the Great Mesoamerican Reef. Mike Beck for TNC

The study, published in the scientific Nature Communications and co-authored by Dr. Michael Beck, lead marine scientist of The Nature Conservancy, found that there are about 200 million people worldwide who get "risk reduction benefits from coral reefs alone or may have to bear higher costs of disasters if the reefs are degraded."

Corals growing© Tim Calver for The Nature Conservancy

"Coral reefs are wonderful natural features that, when healthy, can provide comparable wave reduction benefits to many artificial coastal defenses and adapt to sea-level rise” said Dr. Curt Storlazzi a co-author from USGS. “This research shows that coral reef restoration can be a cost-effective way to decrease the hazards coastal communities face due to the combination of storms and sea-level rise."

The median cost for building artificial breakwaters is USD $19,791 per meter, compared to $1,290 per meter for coral reef restoration projects. Sounds like a good investment, no?

The view of the Pacific Ocean across the reef crest on Ant Atoll at low tide.© Nick Hall for TNC

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