Electrified Reefs May Bring Coral Reefs Back
Bora Bora, Society Islands, French Polynesia—I dove yesterday in the beautiful lagoon that surrounds the tall island of Bora Bora to have a firsthand look at how the coral reef is doing around this South Pacific resort island. The report is not good. Descending to 90 feet, it comes clear that the reef has been hammered in the past few years. I’ve dived here every year for the past decade and have seen incredible decay.
I spent most of the morning observing the still-growing reef system just 10 to 30 feet below the surface. Although the waters are warm and magnificently clear, invasive predators and natural disaster have taken big tolls. Populations of acanthaster—more popularly known as the Crown of Thorns starfish—mysteriously arrived in Polynesia in 2006. Here in the shallows surrounding Bora Bora—as they have done to reefs on nearby Moorea, Raiatea-Tahaa, Huahine and Maupiti—the predatory starfish have eaten, thus killed, hundreds of acres of coral.
In February 2010, natural disaster in the form of Cyclone Oli compounded the destruction done by the starfish. Seas were whipped into a froth of 18 to 21 feet, pouring over the protective reef and across the lagoon. Corals as deep as 100 feet below the surface were devastated.
At 20 feet below, the coral was ripped off at its base and forever destroyed. Today, much of the shallow lagoon floor is covered by a fine pale yellow algae mat. The deeper you dive, the less destruction you see, but the powerful storm—the first cyclone to hit here in 14 years—still broke, mangled and killed deep coral. The one slight upside is that Cyclone Oli was also hard on the starfish population.
My dive corresponded with having just read a new report from the D.C.-based World Resource Institute—“Reefs at Risk Revisited”—that suggests 75 percent of the world’s coral reefs are threatened by local and global pressures. The report blames climate change, specifically warming seas and ocean acidification, but points fingers primarily at human pressures—overfishing, coastal development and pollution. Hurricanes and invasive starfish are not mentioned.
Around the globe, more than 275 million people live within 18 miles of coral reefs. In more than 100 countries and territories, reefs protect 93,000 miles of shoreline, defending coastal communities and infrastructure against storms and erosion.
The reef encircling Bora Bora protects the island from typical weather and seas. Human pressure on the reef and lagoon come from development: Thirteen big hotels have been built on the mainland and its several big motus. In the past decade, the human population has swelled to 9,000, thanks to tourism. But the twin pressures of more building and more people are directly impacting the very thing—the amazing natural beauty—that attracts visitors in the first place.
My morning dive ended in a late afternoon conversation with French-German marine biologist Denis Schneider. Despite his mainland birth, Schneider has been an island-rat most of his adult life. He guesses he spends 30 hours a week—five hours a day, six days a week—in the ocean. His company—Espace Bleu—works to rebuild reefs in Indonesia, the Maldives and Bora Bora.
“The three biggest problems for the reef here—before the starfish arrived—were people,” says Schneider, “especially fishermen and their motors, the red tide which warms the water and kills the coral, and hurricanes.” He and his team have taken on the task to clear out the venomous starfish. “Touch a sea urchin, and the sting will last for a few minutes,” he says. “Brush your skin against a Crown of Thorns, and it will sting for months.” The solution to ridding the lagoon of the starfish is injecting them one by one, using giant hypodermic needles, with a chemical solution that kills them. (Schneider changes the subject when I ask what impact the chemicals may have on the lagoon ….)
To try and resuscitate reefs, especially near the hotels, Schneider and compatriots from the Maryland-based Global Coral Reef Alliance build unique domes out of rebar which they flip over and sink to the lagoon floor. The metal rusts very quickly, and a covering of chicken-wire mesh is soon grown over by calcium-rich marine life. A low voltage current courses through the metal structure, usually created from solar, wind or tidal sources, to encourage fast-growing coral. Within a year, the faux reef is nearly completely covered with colorful, living coral. The patented “electrified” system is dubbed Biorock.
“What we are building are really ‘boosters’ for the reefs, growing three to five times faster than normal coral,” says Schneider. “In some cases 20 times faster.”
The Biorock system is just one of a variety of man-made attempts around the world to encourage new coral growth, including concrete forms and dumped buses, tanks and aging military boats.
“The reality in Bora Bora is that the island, like all in Polynesia, is sinking. Slowly, very slowly,” explains Schneider. “But in 70,000 years, the island will be gone. All that will remain will be the reef surrounding the lagoon. I wish we could come back then and see how the coral has done.”
(For the rest of my dispatch go to takepart.com)