When Hurricane Wilma struck Mexico’s coast in 2005, the shoreline had a natural form of protection: the Meso-American reef, which stretches for 625 miles along Mexico, Honduras, Guatemala and Belize. A 2006 study found that the reef absorbed 99 percent of wave energy before the waves ever hit the shore.
A new study, which reviewed this research and 26 papers, found that around the world, reefs, on average, reduce wave energy by 97 percent, protecting shores and the towns near them from erosion, storm surges and flooding. The researchers also compared the cost of restoring dying reefs, which involves creating structures for reefs to grow, to building artificial seawalls, and found that artificial barriers on average cost about 10 times more than coral restoration.
“You're working with your existing natural seawall, the seawall that nature gave you,” Mike Beck, lead scientist on the Nature Conservancy’s marine team and co-author of the research, told weather.com.
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Individual corals are tiny living organisms that attach themselves to existing structures. Some secrete skeletons of calcium carbonate, and over time — hundreds or thousands of years — those secretions slowly build up into miles and miles of reef, like a naturally created cement wall covered in a “thin living skin” of coral, Beck said. But the difference between a reef and a cement wall is that a healthy reef can build and repair itself, something a human-built barrier can never do.
“If you can get [the reef] back and growing, it can repair itself, it can keep up with changes in sea level,” Beck said. “Those are things that an artificial breakwater cannot do. So you will always have to reinvest in your sea wall or breakwater.”
Cancun, for example, invests about 70 million dollars every five years to restore its coastline, Beck said, in part due to the fact that human activity and development has damaged its near-shore reefs. Without the reef to protect the shore from waves, beaches suffer increased erosion as the sand washes out to sea.
Restoring coral reefs near shore, then, may be a cheap and effective way to protect the 197 million people living at low elevations within 50 kilometers (31 miles) of reefs, whose communities depend on the reefs for shoreline protection and economic benefits.
The role of the reefs in breaking waves and protecting shorelines from erosion and flooding is incredibly important,” Beck said, “but those people also rely on the reefs for fisheries, for tourism, for many other benefits as well.”
The research is published in the journal Nature Communications.
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