Climate

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

Hurricane season has begun, and it’s off to a frightening start.

On Wednesday morning, Beryl — a Category 4 storm and the first named hurricane of the year — was churning toward Jamaica, where it’s expected to make landfall later today and bring life-threatening wind and flooding. Earlier in the week, Beryl pummeled islands in the southeast Caribbean, including Grenada and St. Vincent and the Grenadines. It flattened buildings, wiped out electricity, and left at least four people dead. Heavy rainfall from the storm has also killed another three people in Venezuela.

Hurricane Beryl is already record-breaking. On Tuesday, Beryl intensified into a Category 5 storm, before slowing back down Wednesday, making it the earliest Category 5 storm on record in the Atlantic. The storm, which is expected to reach the Cayman Islands by Thursday, also intensified at record speeds for a storm this early in the year, jumping from Category 1 to Category 4 in less than 24 hours.

Caribbean nations are particularly vulnerable to hurricanes, for the obvious reason that they’re often in the path of these storms. Hurricanes typically form in the Atlantic Ocean, west of northern Africa, and then travel west toward the Caribbean and Southeastern US.

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.

An all-natural hurricane defense system

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.

This service — which coral reefs supply for free — is worth a lot.

Across the US, including Puerto Rico and other Caribbean islands, coral reefs help safeguard the homes of more than 18,000 people and avert $1.8 billion in flood damage each year, according to a 2019 study by the US Geological Survey (USGS). Slightly older research found that, globally, this number is more than $4 billion.

“Without reefs, annual damages would more than double,” authors of the latter study, published in Nature Communications, wrote.

Caribbean nations are among those that benefit most from coral reefs and the damage they prevent. In the Nature Communications study, published in 2018, researchers ranked countries by how much flood damage coral reefs avert, relative to their GDP. Eight of the top 10 are Caribbean nations.

No. 3 is Grenada, where Hurricane Beryl made landfall Monday.

Vanishing reefs

All the financial and potentially life-saving benefits reefs provide make losing them that much scarier. And we are indeed losing them, especially in the Caribbean’s warm(ing) waters.

The area of live hard corals on Caribbean reefs has fallen by about 80 percent in recent decades. In some regions, like the Florida Keys, the declines are even steeper. Compared to the 1970s, most Caribbean reefs are almost unrecognizable today.

Elkhorn coral — a species resembling moose antlers known for its wave-weakening abilities — is especially endangered. In the 1970s, it grew across more than 30 percent of Caribbean reefs. By the 1980s, coverage of the coral had fallen to less than 2 percent, a number that has likely only shrunk further in the years since.

A number of human behaviors have destroyed Caribbean coral, from coastal construction to fishing, as have some seemingly natural threats, like disease. The most enduring and existential problem, however, is climate change.

Warming ocean water disrupts the relationship between coral and a kind of symbiotic algae that lives inside the polyps. This disruption causes coral to turn white — or “bleach” — and starve. Bleached corals often have more trouble surviving other threats and die.

That means climate change is not only making tropical storms more severe, but it can also weaken our natural defenses against them. And this is an important, frightening point: A warming ocean makes storms more dangerous, not just because they’re intensifying faster or dropping more rain but because, in places like the Caribbean, we’re losing resilience that iconic ecosystems provide.

Update, July 3, 10:15 am ET: This story was originally published on July 1 and has been updated multiple times with the latest information about Hurricane Beryl.

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