The World Without Us

Jackson’s impression radically changed, however, when he jumped into the water. “I could barely see 10 percent of the bottom,” he told his Scripps colleague Enric Sala when he returned. “My view was blocked by sharks and big fish. You have to go there.”

Sala, a young conservation marine biologist from Barcelona, had never known big sea species in his native Mediterranean. In a strictly policed reserve off Cuba, he had seen a remnant population of 300-pound groupers. Jeremy Jackson had traced Spanish maritime records back to Columbus to verify that 800-pound versions of these monsters once spawned in huge numbers around Caribbean reefs, in the company of 1,000-pound sea turtles. On Columbus’s second voyage to the New World, the seas off the Greater Antilles were so thick with green turtles that his galleons practically ran aground on them.

Jackson and Sala coauthored papers describing how our era’s perspective had deluded us into thinking that a coral reef populated by colorful but puny, aquarium-sized fish was pristine. Only two centuries earlier, it was a world where ships collided with whole schools of whales, and where sharks were so big and abundant they swam up rivers to prey on cattle. The northern Line Islands, they decided, presented an opportunity to follow a gradient of decreasing human population and, they suspected, increasing animal size. At the end closest to the equator was Kiritimati, also known as Christmas Island, the world’s largest coral atoll, with 10,000 people on just over 200 square miles. Next came Tabuaeran (Fanning) and a 3-square-mile speck called Teraina (Washington), with 1,900 and 900 people, respectively. Then Palmyra, with 10 staff researchers—and 30 miles farther, a sunken island where only the fringe reef that once encircled it remained: Kingman.

Other than copra—dried coconut—and a few pigs for local consumption, there is no agriculture on Kiritimati-Christmas Island. Still, in the first days of the 2005 expedition that Sala eventually organized, researchers aboard the White Holly were startled by the gush of nutrients from the island’s four villages, and by the slime they found coating the reefs where grazers like parrotfish had been heavily fished. At Tabuaeran, rotting iron from a sunken freighter was feeding even more algae. Tiny Teraina, far overpopulated for its size, had no sharks or snappers at all. Humans there used rifles to fish the surf for sea turtles, yellowfin tuna, red-footed boobies, and melonhead whales. The reef bore a four-inch-thick mat of green seaweed.

Submerged Kingman Reef, northernmost of all, had once been the size of Hawaii’s Big Island, with a volcano to match. Its caldera now lies below its lagoon, leaving only its coral ring barely visible. Because corals live in symbiosis with friendly, one-celled algae that require sunlight, as Kingman’s cone keeps sinking, the reef will go, too—already its west side has drowned, leaving the boomerang shape that allowed the White Holly to enter and anchor in the lagoon.

“So ironic,” marveled Jackson, after 70 sharks greeted the team’s first dive, “that the oldest island, sinking beneath the waves like a 93-year-old man with three months before he dies, is the healthiest against the ravages of man.”

Armed with measuring tape, waterproof clipboards, and three-foot PVC lances to discourage toothy natives, the teams of wet-suited scientists counted corals, fish, and invertebrates all around Kingman’s broken ring, sampling up to four meters on either side of multiple 25-meter transect lines they lay beneath the transparent Pacific. To examine the microbial base of the entire reef community, they suctioned coral mucus, plucked seaweed, and filled hundreds of liter flasks with water samples.

Besides the mostly curious sharks, unfriendly snappers, furtive moray eels, and intermittent schools of five-foot barracuda, the researchers also swam through swirling shoals of fusiliers, lurking peacock groupers, hawkfish, damselfish, parrotfish, surgeonfish, befuddling variations on the yellow-blue theme of angelfish, and striped, crosshatched, and herringbone permutations of black-yellow-silver butterfly fish. The huge diversity and myriad niches of a coral reef enable each species, so close in body shape and plan, to find different ways to make a living. Some feed only on one coral, some only on another; some switch between coral and invertebrates; some have long bills to poke into interstitial spaces that conceal tiny mollusks. Some prowl the reef by daylight while others sleep, with the whole assemblage changing places at night.

“It’s kind of like hot-bunking in submarines,” explains Alan Friedlander of Hawaii’s Oceanic Institute, one of the expedition’s fish experts. “Guys take four-to-six-hour shifts, switching bunks. The bunk never stays cold for very long.”