National Geographic : 2014 Apr
68 national geographic • April 2014 biodiversity, France curbs illegal fishing and turtle poaching. Military garrisons and a gendarmerie maintain a presence on several of the islands— Europa included—and naval ships patrol their waters. Although Europa and Bassas da India lie close together in the middle of the Mozambique Channel, they are very different places. Europa is a scrub- covered island that is home not only to nesting turtles but also to a million breeding pairs of seabirds. Bassas is an atoll that barely shows above the wa- terline and has a shark-filled lagoon the size of Manhattan. Both are among the last vestiges of healthy marine ecosystems in the western Indian Ocean— sanctuaries for wild nature in depleted seas. “On the surface these places look like nothing—like insignificant dots,” says marine biologist Thomas Peschak, who photographed this article. “But once you’ve dived here, you’re spoiled for the rest of your life.” The two islands occupy an expanse of ocean whose vexing currents and eddies have challenged mariners for centuries. Today’s marine scientists have found a way to study this environment without even going to sea. Because of the close ecological connection between seabirds and marine life, they can use birds as proxies for open-water species such as tuna. Many seabirds rely on these ocean-roaming hunters to drive prey to the surface, within reach of their bills and talons. Boobies and terns form low-flying flocks that track marine life from just above the surface. These network foragers fan out from their roosts on land, keeping each other in sight, ever alert in case one should encounter prey. Other species track the trackers, soaring to high altitudes to survey the pan- orama. Frigatebirds are supreme among the high fliers. These exceptional Bassas da India (FRANCE) Lagoon Reef exposed at low tide Sand exposed at low tide Sandy islets barely above water Reef submerged at low tide 21°30′S 39°42′E Coral heads Coral reef SANTIAGO SHIPWRECK (1585) 0mi 1 0km 1 Bassas At high tide only a few rocks show above the waterline at Bassas da India. When the tide ebbs, it exposes a ring of coral 300 feet wide and six miles in diameter. This atoll is the summit of an undersea volcano that rises from the seabed 10,000 feet below the surface. Frequent contributor Kennedy Warne specializes in stories about nature and the environment. Thomas P. Peschak is director of conservation for the Save Our Seas Foundation, which facilitated his photographic coverage of the atolls.