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Coral Reefs: the Seawall That Nature Built

Wave breaking over a healthy coral reef in Tumon Bay Marine Preserve, Guam, Mariana Islands. Photo credit: Curt Storlazzi
Wave breaking over a healthy coral reef in Tumon Bay Marine Preserve, Guam, Mariana Islands. Photo credit: Curt Storlazzi, U.S. Geological Survey

By Dr. Michael Beck, lead marine scientist, The Nature Conservancy

Here’s an optimistic idea for you to consider: We can save our coral reefs.

Yes, you read that correctly. We can, and indeed we must, save coral reefs to help protect ourselves. Admittedly, that’s not your traditional rationale for conservation, but it is one that will still yield all the benefits to nature by recognizing their benefits beyond nature. This new rationale also requires that we value reefs differently – based on location, size, productivity, and risk reduction potential.  Indeed some reefs are far more critical to conserve and restore – and, importantly, could likely attract more resources to do so – due to their outsized benefits to people.

Today, the human and financial costs of coastal flooding and erosion are rising drastically, due to a combination of risky coastal development choices and impacts of a changing climate. Extreme weather events, erosion, and flooding affect (i) hundreds of millions of vulnerable people, (ii) critical infrastructure, such as bridges and roads, and (iii) key coastal industries, such as fisheries and tourism.. Coastal and marine habitats, particularly coral reefs and wetlands, are at the front line of many of these changes and are increasingly degraded or destroyed. Governments are spending billions of dollars to reduce risks from these coastal hazards and climate change, usually to build infrastructure like seawalls, dikes and breakwaters.

Perversely, many of these investments in built infrastructure further degrade our first line of coastal defense – our reefs and wetlands.

Yet herein, lays the opportunity.

Leaders across the world are actively seeking solutions that more cost-effectively reduce risks from coastal hazards. These include leaders across major municipalities spread from Miami to Jakarta and across lenders like the World Bank and the Inter-American Development and the Prime Ministers of Small Island Developing States such as Grenada and the Bahamas.

Healthy coral reefs can be a part of the solution.

Recently published research shows that coral reefs on average reduce wave energy by a full 97 percent – stopping the bulk of waves that would otherwise hit shorelines, which could help protect roughly 200 million people across some of the most populous nations in the world including the USA. You can see where these people are on this map. These coastal communities must bear the higher costs of disasters if their reefs are degraded or lost.

Most importantly, we are finding that communities can cost-effectively improve their coral reef defenses.

The median cost for building artificial breakwaters in the tropics is USD $19,791 per meter, compared to $1,290 per meter for coral reef restoration projects — echoing similar findings by the reinsurance and planning industries. And, that’s not even considering the other co-benefits to fishing and tourism industries, for example (would your family rather snorkel near a coral reef or seawall?).

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Coral reef off Restoff Island in Kimbe Bay, West New Britain, Papua New Guinea.
Credit Mark Godfrey, The Nature Conservancy

OK, admittedly, most people don’t picture waves being stopped by corals in the same way a sea wall might stop a wave.  But this is exactly what is happening when you see a wave break on a coral reef.  Maybe you have seen pictures of surfers on these waves and you see the whitewash that remains after the wave breaks.

Recognizing that reefs provide coastal defense provides many new opportunities to invest in this natural sea wall as part of a blend of risk reduction strategies. These funds include those for climate adaptation (critical to many island nations) as well as the more traditional hazard mitigation funds that would go to seawalls or breakwaters (such as projects by Port Authorities, Transportation Agencies, US Army Corps of Engineers, and FEMA).

A greater appreciation of the effectiveness AND cost effectiveness of reefs for coastal defense should help motivate the local and global actions needed to maintain and restore these ecosystems and the services they provide. A management focus on reefs with joint goals for adaptation, risk reduction and conservation, however, will require changes in how we have traditionally approach reef conservation. While conservation efforts are most often directed to more remote reefs, we suggest there should also be a focus on reefs closer to the people who will directly benefit from reef restoration and management.

We must capitalize on the value coral reefs provide to people. If we value them properly, we can indeed save them.

The study published in the journal Nature Communications, is co-authored by an international team of researchers from the University of Bologna, The Nature Conservancy, United States Geological Survey, Stanford University and University of California Santa Cruz.