The Caribbean has a defense system against deadly hurricanes — but it’s vanishing

But Caribbean islands also have one of the world’s best defense systems against superstorms like Beryl. That system is hidden under the waves, it’s free, and it’s all-natural. It’s coral reefs.

Indeed, most Caribbean nations are surrounded by a colorful patchwork of coral reefs, communities of living animals that function together as natural seawalls. These hard, rocklike creatures help dampen waves and reduce flooding. Research shows that coral reefs help dozens of countries avert billions of dollars in flood damage each year, in the Caribbean and globally.

The problem, more pressing now than ever, is that these lifesaving ecosystems are vanishing — for the very same reason hurricanes are becoming more destructive.

Each piece of coral on a reef is actually a colony of tiny animals, called polyps. Those polyps build skeletons out of calcium carbonate, not unlike a snail growing a shell, that form the structure of the reef.

It’s these coral skeletons that safeguard coastlines during a storm.

Simply put, waves lose energy when they ram into coral reefs. The bigger and taller the reef, the more wave energy it dissipates, for the same reason that coastal cities use breakwaters made of rocks to protect the shoreline. Remarkably, studies show that coral reefs can dissipate more than 90 percent of wave energy. Waves with less energy are smaller and slower and don’t deal as much damage when they reach the shore.

Even a small difference in a reef’s height can make a big difference in risk. Flood risk is often measured by what’s called the 100-year flood zone — an area in which the chance of a flood in a given year is 1 percent. If coral reefs in the US lose 1 meter of height, a study found, that zone in the US would grow by 104 square kilometers (or about 26,000 acres, nearly twice the size of Manhattan), putting about 51,000 more people at risk of flooding.