A report by Andrea Thompson for Live Science.
The Caribbean is used to hurricanes, but not hurricanes like Irma, one of the strongest storms on record in the Atlantic Ocean basin. The top-end Category 5 hurricane, which had winds of 185 mph (298 km/h) at its peak, raked across successive islands, leaving catastrophic damage in its wake.
The scars left by the storm are still being catalogued, because of delays caused by downed communications and the difficulty still faced in getting to some islands. And those effects will show for some time, experts said. Now the region is being pummeled by Hurricane Maria, and there are still several months of hurricane season left. With this year’s hurricane seasonalready proving to be more active than normal, how will this part of the world recover?
“It’s going to take not just months, but years” for many of these islands to get back to where they were pre-Irma, said Steve Bowen, director of impact forecasting at the reinsurance company Aon Benfield. [Hurricane Irma Photos: Images of a Monster Storm]
Not only were roofs ripped from houses and power lines torn down, but vegetation was also stripped away from trees, turning once-verdant islands brown. Coral reefs were also likely damaged and beaches eroded, experts said.
Irma was “one of the most damaging hurricane events to ever track through the Caribbean,” Bowen told Live Science.
In the crosshairs
The Caribbean sits in prime hurricane territory, with storms regularly sweeping through the area. Many of the islands are small and flat, which means the land surface does little to affect storms, unlike mainland areas or even larger islands like Cuba, where terrain can tear up a storm.
“Those islands, of course, are basically sitting ducks for hurricane events,” Bowen said.
Hurricane Irma’s track took it across first Barbuda, then the split French and Dutch island of St. Martin/Sint Maarten, St. Barthélemy, Anguilla, and the British and U.S. Virgin Islands. The monster storm clipped Puerto Rico, which avoided the worst damage; hit the Turks and Caicos Islands with its northern eyewall; then swept across the Bahamas and along Cuba’s north coast before heading toward Florida.
The highest wind speed measured during the storm was 155 mph (249 km/h), recorded by an anemometer on Barbuda that subsequently stopped transmitting data, presumably because it was blown away, according to Aon Benfield’s report on the storm.
On Barbuda, 95 percent of structures were destroyed, according to the prime minister of Antigua and Barbuda, “which is horrific,” Bowen said. Other islands saw between 65 percent and 75 percent of structures destroyed, a level Bowen said he still considered catastrophic. Power was knocked out, drinking supplies were impacted and roads were left impassible across the affected islands.
But human structures weren’t the only things affected. The coral reefs that lie offshore of some islands were likely damaged as well, scientists said. [The 20 Costliest, Most Destructive Hurricanes to Hit the US]
These reefs offer natural protection to the islands, absorbing energy from the storm’s waves, slowing the waves down and reducing inundation to the islands. But a Category 5 storm, particularly one as strong as Irma, is generally too much for the reefs, experts said.
“Basically, it breaks the coral reef apart,” Cheryl Hapke, a scientist with the U.S. Geological Survey (USGS), told Live Science. After other really large storms, scientists conducting surveys “find that some of the reefs are just basically rubble,” she said.
Runoff from land can also damage reefs, because “you can get huge amounts of pollutants and nutrients” that upset the delicate balance between corals and their symbiotic algae, said Konrad Hughen, an associate scientist at the Woods Hole Oceanographic Institute in Massachusetts. Sediment can also smother the reefs; even a centimeter-thick layer of silt “will be devastating,” Hughen said.
Sometimes, though, hurricanes can benefit reefs: As hurricanes churn over the ocean, they dredge up deep water, which is cooler than surface water. Unusually warm water can cause bleaching in reefs (where the coral expels its algae and can starve), and for these reefs, the cooler water can provide relief, Hughen said.
The waves and surge generated by a storm like Irma can also wash sand away from beaches, Hapke said, a major concern in an area whose economy depends on tourists coming to enjoy those beaches. Sand can be replenished ¾ as it was along New Jersey’s coast after Hurricane Sandycaused major erosion in 2012 ¾ but that is more difficult to do in the Caribbean, where there aren’t as many sources of sand, Hapke said.
Sea-level rise compounds this problem, because with higher sea levels, “you’re going to have more erosion and more inundation than we had” even two decades ago, she said.
Storm surge that washes over the islands can also infiltrate freshwater aquifers and kill off vegetation, such as grasslands.
Outside of its impacts to homes and other structures, Hurricane Irma’s most noticeable impact is the way its winds stripped vegetation from the islands. In satellite comparisons, a dull brown replaces the lush, tropical greens from before the storm. Salt spray may also have killed off some vegetation, something Hapke said she noticed on New York’s Fire Island after Sandy.
The recovery time of all these natural systems will likely vary. Vegetation will likely rebound fairly quickly as the ground dries up and rains wash out some of the salt left by ocean surge, Hapke said.
“In the tropics, things grow very rapidly,” she said. They’re also adapted to the odd extreme event.
“These ecosystems are used to these types of events, so you know they’ll come back,” she added.
Reefs will likely take longer to recover, particularly if they are battling other issues, like bleaching or pollution. Corals grow only up to a few centimeters per year, “and that’s when they’re large, established corals,” Hughen said. Reefs that are wiped out and relying on new corals to recolonize them will take a long time to recover.
Hurricane Maria is now barreling through the Caribbean, threatening some of the same islands already reeling from Irma, particularly the U.S. Virgin Islands. Repeated blows from hurricanes can prolong the time needed for recovery, both for human populations and natural ecosystems, Hapke said, because they are being battered while in an already-weakened condition.
“It just extends the amount of time for that system to recover,” she said.
Original article on Live Science.