The Beacon

Guest Post: Bora Bora’s Threatened Reefs

The island of Bora Bora in French Polynesia. Image via Wikimedia Commons.

Guest blogger Jon Bowermaster is a writer and filmmaker. In this post, Jon reports on the state of corals in Bora Bora.

Bora Bora, Society Islands, French Polynesia – I dove last week in the beautiful lagoon that surrounds the tall island to have a first hand look at how the coral reef is doing in this South Pacific resort island. The report is not good.

Descending to 90 feet, it was immediately clear that the reef has been hammered in the past few years. I’ve come here every year for the past decade and have seen incredible change.

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 both taken big tolls.

Populations of acanthaster -- also known as the crown-of-thorns starfish – mysteriously arrived in Polynesia in 2006. No one is sure exactly how they got here or where they originated, though invasive species are well known for hitching rides on cargo ships and jumping off far from home. 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 devoured hundreds of acres of coral.

The aforementioned natural disaster occurred in February 2010, when Cyclone Oli whipped the nearby seas to a froth of 18 to 21 feet, pouring over the protective reef and across the lagoon. The impact on the corals was devastating, as deep as 100 feet below the surface.

At 20 feet below, the coral was ripped off at its base and forever destroyed. Rather than coral, today much of the shallows of the lagoon floor are covered instead 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 fourteen years -- still managed to break, mangle and kill coral. The only slight upside is that it was also hard on the starfish population.

My dive corresponded with having just read a new report from the World Resource Institute – “Reefs at Risk Revisited” – which suggests that 75 percent of the world’s coral reefs are currently threatened by local and global pressures, including climate change, ocean acidification, overfishing, coastal development and pollution.

Around the globe more than 275 million people live in the direct vicinity (within 18 miles) of coral reefs. In more than 100 countries and territories reefs protect over 93,000 miles of shoreline, helping defend coastal communities and infrastructure against storms and erosion.

The reef encircling Bora Bora helps protect the island from typical weather and seas. In the past decade the human population has swelled to 9,000, thanks to tourism. But the pressure of development is having a direct impact on the very thing – its amazing natural beauty – that attracts visitors in the first place.

To try and resuscitate reefs, the Global Coral Reef Alliance is building unique domes out of rebar which they flip over and sink to the lagoon floor. The metal rusts very quickly and the chicken-wire mesh covering it is soon grown over by calcium-rich marine life. Coral is transplanted onto the faux reef and within a year it is nearly completely covered with colorful, living coral.

To encourage fast-growing coral a low-voltage current courses through the metal structure, usually created from solar, wind or tidal sources. This system is just one of a variety of man-made attempts being made around the world to encourage new coral growth, including concrete forms and, around the coast of the U.S., purposely dumped buses, tanks and aging military boats.

You can read an extended version of this post at Jon Bowermaster’s blog.

 


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