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Can the crown jewel of world's coral reefs be saved?

Scientists and politicians are moving to protect the enormous biodiversity in the Coral Triangle – a critical marine nursery for tuna and other species.

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Here amid the shallow-water coral formations off Nusa Lembongan, those pressures seem remote, despite the handful of resorts nestled in the nearby cove. With a diving mask as a picture window and fins for propulsion, visitors' views take in corals that branch, spread platelike, or lay like arrays of flattened cabbage leaves daubed in pastel greens, purples, pinks, and muted russets. A giant clam is half buried near the base of one coral head, while sergeant major fish, surgeonfish, and schools of anthias flit past.

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Indeed, one of the factors driving efforts to preserve this small patch of the Coral Triangle is its remarkable variety of marine life, notes Rili Djohani, The Nature Conservancy's country director for Indonesia. The organization is one of three international environmental groups working with regional governments and aid organizations to protect biologically critical spots in the triangle. The group performed a rapid ecological assessment and found that the diversity of coral species here was among the highest in the Coral Triangle. Currents running past Nusa Lembongan and two sister islands bring nutrients up from the deep ocean, turning the seas around them into a five-star feeding ground for dolphins, sharks, rays, and other fish.

Putting it high on the list of coastal areas to preserve "was a no-brainer for us," Ms. Djohani says.

How amazing diversity developed

The story of how this region acquired such biodiversity is thought to begin 55 million years ago, when the three largest Philippine Islands each sat about 1,000 miles apart. As crustal plates shifted, the islands drew closer together. Each island brought with it its own unique blend of marine species. "Most of the species we see today came into existence during this dramatic movement," Carpenter says.

With the coming and going of four ice ages between 1.8 million and 11,500 years ago, sea levels changed dramatically. During the last glacial maximum some 17,000 to 18,000 years ago, for instance, global sea levels were nearly 400 feet below today's levels. This exposed land bridges among several major islands in the Coral Triangle, effectively isolating large groups of marine species, which continued to evolve under new environmental conditions. Once sea levels rose again, the new species rejoined the wider population. Also, two of the most powerful equatorial currents on Earth pass through the region. The currents split and carry larvae from fish, mollusks, and corals over great distances, delivering them to new habitats where – if they survive – they can embark on new evolutionary paths.