Islands of Hope

Chapter One

A Perfect Park

Bonaire Marine Park, Bonaire, Netherlands Antilles

What do you do when the temperature dips and your friends Jim and Martha Foght head for their winter home in the Caribbean? Well, you can stew in the green juices of your envy or go into convulsions of sun-deprived self-pity. Or you can invite yourself down for a week. Which is how I got acquainted with the island of Bonaire.

I start today as I start every day on the island: drinking coffee in my bathing suit and watching perky, yellow-breasted banana quits swirl from feeder to feeder on the Foghts' patio. Then I climb down the ladder that leads from their backyard to the sea, slip on mask and flippers, and slide into the warm, turquoise waters of Bonaire Marine Park, one of North America's best-preserved sanctuaries.

I snorkel over white sand and coral rubble. Silvery needlefish hang motionless at the water's surface, and trunkfish peck away at the algae that coats the coral litter. The water deepens, and the landscape beneath my mask changes to great racks of tan elkhorn coral spotted with red algae. In the blue-green haze ahead, a barrier of tightly packed elkhorn coral marks the reef crest. A stoplight parrotfish, its coarse scales ablaze with yellows, greens, and blues, crunches dead coral, then excretes a puff of white sediment, the raw material of the Caribbean's white-sand beaches.

Scattered boulders of brain coral mix with staghorn and elkhorn coral. But these are only the obvious species of corals; dozens of others live here, too, from fire coral to flower coral. There are also sponges, sea fans, and lamp shells. And in the crevices and interstices of coral skeletons live worms and urchins, shrimps and crabs. Schools of electric-blue chromis swarm through this jungle, and wrasses are everywhere. Shells once inhabited by living invertebrates lie passively on the sea floor. As usual, this conflation of life and death reminds me of an old-growth forest, where decay and rebirth dance together in a waltz so intricate that it bewilders the eye.

I head for deeper water. The reef crest, a jumble of jagged corals bound together by encrusting coralline algae and fire coral, rises from the sea floor to within a foot or two of my pale, vulnerable belly. I kick harder and pass over without mishap. Then the reef falls away. Beyond it is blue, deep ocean.

I turn ninety degrees and swim parallel to the reef. It's hard to believe that this massive structure could be built by tiny polyps of coral, which reminds me of something else coral reefs have in common with old-growth forests: both are highly complex ecosystems that take centuries to develop but can be destroyed in the blink of an eye.

* * *

Coral reefs are in trouble the world over. In an irruption probably stimulated by excessive nutrient runoffs, crown-of-thorns starfish are devouring Australia's Great Barrier Reef; pollution, sedimentation, and anchor damage are degrading Florida's reefs; the cyanide used to stun fish to collect them for tropical-aquarium enthusiasts is poisoning corals in the Philippines; and unusually high water temperatures are bleaching coral reefs around the globe. Before these became serious problems, though, Bonaire was vigorously protecting its reefs. And the island's farsighted approach to conservation has paid off; its reefs remain pristine.

As is often the case with conservation success stories, geography and a few determined people played major roles in preserving this ecosystem.

Bonaire is a 111-square-mile, comma-shaped patch of arid land lying about 50 miles north of Venezuela. The comma shelters Klein Bonaire, a much smaller, uninhabited island. Both islands are ringed with reefs. Because Bonaire is south of the hurricane belt, its reefs rarely suffer the damage those storms can inflict. Less geographically lucky sites, such as the Society Islands in the Pacific, regularly have their reefs devastated by hurricanes.

Donal Stewart, known to all Bonaireans as "Captain Don," came to the island in 1962. He was looking for a good place to dive, and because the undisturbed reefs of Bonaire suited him perfectly, he stayed. He was poor at the time, down to smoking cigarette butts and eating canned cranberry sauce for supper. But as he wrote in his memoirs, he wasn't broke: "Sixty-three cents ain't broke. Should a been around during the depression. Zero was broke."

After he recovered financially, Captain Don opened the first dive shop on the island and soon realized that Bonaire could become a popular scuba-diving site. He also realized that hordes of divers anchoring on the reefs could harm the very resource that brought them to the island. Consequently, while diving on Bonaire was still in its infancy, Captain Don placed the first mooring buoy on the island's reefs. And as diving picked up, the island government was quick to understand the value of the reefs in attracting tourists.

Bonaire is one of the Netherlands Antilles (as are Curaçao, Saba, St. Eustatius, and St. Maarten), which are a territory of the Netherlands. The Netherlands Antilles are governed by a democratically elected parliament, but an island council manages Bonaire's local affairs. The council meets in Kralendijk, the island's capital and only sizable town. In 1971, the council banned spearfishing, an act comparable to forbidding deer hunting in Michigan. In 1975, it stopped all coral collecting. Four years later, helped by a grant from the World Wildlife Fund, Bonaire Marine Park was established.

From the very beginning, the park took a no-nonsense approach to conservation. First, its management decided to protect all of Bonaire's reefs, even though development and diving threatened only a few. This made enforcement of the park's rules easier. "For example," explained the park's first manager, Tom van't Hof, "if coral collecting is prohibited in the marine park and the park only included the reefs of Klein Bonaire, a diver caught outside his hotel unloading some fresh trunks of black coral could allege to have collected outside the park boundaries. By applying the same regulations to all reefs, this is not possible."

Today, the marine park encompasses the sea bottom and overlying waters from the high-water mark to the sixty-meter (two-hundred-foot) depth contour. Anchoring, spearfishing, and live-shell and coral collecting are forbidden; divers and snorkelers are warned to avoid even touching the corals; and Captain Don's one mooring buoy has grown into a string of seventy-five public dive moorings along the leeward shore of the island. The number of divers has grown, too, but thanks to the conservation measures pushed by Captain Don, Tom van't Hof, and others--and supported by the enlightened citizens of Bonaire--the reefs are essentially unchanged.

* * *

The next morning, I'm back in the sea again, snorkeling over the reef. I love this ecosystem, the otherworldliness of its extensive and ever-changing cast of characters. Charles Birkeland, a scientist at the University of Guam, maintains that "coral reefs have the greatest species diversity per square meter of any community on Earth." Of course, it is this aspect of coral reefs that makes them so popular; divers would be rare if all sea bottoms were sand.

But the complexity of the ecosystem makes it almost impossible to grasp what's going on. Even food-chain relationships, which are often simple on land, are complicated here. As if to underscore the point, a spectacular parrotfish, a glowing blue male, appears beneath me, biting enthusiastically at the coral.

Members of the family Scaridae, parrotfish are large (up to four feet long), blunt headed, and brightly colored, with large scales and fused teeth. Their dazzling hues and beaklike mouth apparently reminded some heat-addled tropical explorer of a parrot, hence their common name. Parrotfish hang around coral reefs throughout the world. Males and females of the same species are often quite different in appearance, and young parrotfish have a disturbing habit of changing sexes and colors. To complicate matters further, some sexually mature female parrotfish undergo a final growth spurt in which they change colors and sexes again. They also grow pugnacious. These oversized fish are like bodybuilders on steroids, and they go by a name bodybuilders would appreciate: supermales . However, the name is only partially accurate; supermales are often poor spawners.

This confusion of colors, sizes, and sexes has caused some folks to surmise that there are far more species of parrotfish than actually exist. In a Smithsonian Institution monograph, Leonard Schultz found 364 species of parrotfish listed in the literature, but his own research led him to conclude that there are actually only 80 species in the world. Consequently, figuring out which parrotfish species live where mightily frustrates ichthyologists. As Schultz noted somberly, "So much misidentification is prevalent for parrotfishes in the ichthyological literature that at present the geographical distribution of each species of parrotfish cannot be worked out in detail."

The confusion is understandable; parrotfish are hard to identify. For example, I'm reasonably certain that the bright aqua fish below me is a blue parrotfish, Scarus coerleus, a plentiful fish in Bonaire's waters. However, supermale yellowtail parrotfish are close to the same color. And though yellowtails are rarer here, there's no way to know for sure which species this is, short of killing it and examining its teeth, scales, and fin spines. And I'd never kill a fish just to learn its name; a live fish of uncertain species is more interesting than a properly identified dead one.

Regardless of species, though, all parrotfish have two things in common: ravenous appetites and bad table manners. They constantly chomp away at the reefs that shelter them, tearing off chunks of coral with an audible crunching sound, pulverizing them, and expelling calcium carbonate. A single parrotfish can consume a pound of limestone in a year. Since the reefs teem with parrotfish, the wear and tear on corals is substantial. So impressed were ecologists by the damage parrotfish (and other organisms) inflict on reefs that they coined a term for the process: bioerosion .

But in this complicated ecosystem, nothing is as it seems. For all their munching and crunching on the reefs, parrotfish do little damage to living coral polyps. They are merely grazing on the algae that coats the coral skeletons. The scraping of their beaks only incidentally erodes the reefs.

Incidental or not, parrotfish can weaken the structure that supports live corals. So it would appear that they are harmful to the corals, albeit unintentionally. But again, appearances deceive. Without parrotfish (and other herbivores) to graze the foliose algae that coats the reefs, the algae would overgrow them and kill the corals. Thus, coral reefs owe their very existence to parrotfish and other algae grazers.

The parrotfish below me doesn't look like the savior of anything. It slides in and out of crevices, appearing and disappearing in the gray-green reef, pecking at coral and doing what millennia of natural selection have programmed it to do. Probably a hundred different organisms are within my view. Microscopic borers, crabs, sponges, and sea stars are all leading shadowy, complicated lives beyond my mask. And each species is playing a part in a great Darwinian epic directed by the reef.

The incredible species diversity is what makes coral-reef ecosystems so interesting to ecologists. The complicated interrelationships among species--like that among parrotfish, algae, and corals--are challenging to figure out. Complex ecosystems like this one can be surprisingly resilient when they are intact, but after they have been altered by man, they heal slowly, if at all.

Take, for example, the strange case of the long-spined sea urchin, Diadema antillarum . This sea urchin is about four inches long and resembles a black pincushion abristle with long, sharp needles. It lives in crevices in coral reefs and grazes on algae and occasionally live corals.

In 1983, the long-spined sea urchins of the Caribbean began to die. The mysterious disease, whose source was never pinpointed, spread rapidly, eventually killing over 90 percent of the population. In many spots, mortality was 100 percent. Within weeks, foliose algae growing on and around the reefs increased by 50 percent. After several years, many corals were overgrown and dying. None of this was a surprise to ecologists; the feeding habits of these sea urchins were well known.

What was surprising was the small effect that the die-off had on healthy reefs, such as Bonaire's. As with other islands in the region, Bonaire's urchins succumbed to the disease. Its corals, however, survived with little damage. The reason was the reefs' robust populations of parrotfish and other herbivorous fish, which enjoyed boom times in the absence of the competing urchins. The islands that suffered the most were those where fishermen had overharvested algae-grazing fish.

This kind of complexity has made scientists understandably cautious about tampering with the natural processes of coral reefs. Mark Hixon, a zoologist at Oregon State University, summed up this attitude in Life and Death of Coral Reefs : "Reef systems may be too complicated to allow us to predict explicit outcomes of human activities ... [so] managers should cast a skeptical and cautious eye on proposals to strongly alter the abundance of any coral reef inhabitant."

Snorkeling toward home in the crystal-clear water above the reef, it is easy to agree with Dr. Hixon about the complicated nature of these ecosystems. Some form of life covers every surface of the reef below me. Most prominent are the corals: the ubiquitous fields of elkhorn and staghorn; great mountains of star coral and little gobbets of golf-ball coral; tube, bush, and scroll corals; and others I can't identify. Though the swarms of brightly colored fish are the main attraction for divers, the corals are the base on which this ecosystem rests. It is the corals that build the reefs, and it is the reefs that supply the crannies and nooks where fish hide. The reefs also provide the solid structure on which algae grow, and they protect all of their inhabitants, including the coral polyps themselves, from predators and the swirling currents of the open sea.

In fact, reefs are an ideal environment for many organisms. So useful are they that the earliest known life on our planet formed reefs.

* * *

Stromatolites are stubby columns of finely layered limestone fifteen or so inches tall. They bear an uncanny resemblance to a stack of very thin pancakes. Geologists have long been aware of stromatolites but disagreed about their origin. Some thought they were fossilized structures created by living creatures; others thought they were merely unusual rock formations. The question was an important one because some stromatolites are ancient. In Australia, scientists have discovered stromatolites that are 3.5 billion years old, which means they were formed only a few hundred million years after the earth's crust solidified. If living organisms created them, then they would be the earliest form of life known.

The nature of fossilized stromatolites wasn't determined until the early 1960s, when a geology graduate student named Brian Logan discovered living stromatolites in the shallow waters of Shark Bay off the coast of Australia. Although modern stromatolites had been investigated as early as 1933, those at Shark Bay were remarkable because they bore an unmistakable resemblance to fossilized stromatolites. The new evidence swayed most scientists, who now generally accept that fossilized stromatolites were created by living organisms.

Living stromatolites (and presumably ancient ones) are composed of thin layers of algal mats. The top layer is a sticky surface of photosynthetic cyanobacteria once called blue-green algae and known colloquially as pond scum. As sediment builds up on the gummy uppermost layer, the algae migrate upward, toward the life-giving sun, leaving an oxygen-depleted zone in which anaerobic microbes thrive. Over centuries, this process produces a finely layered stromatolite.

Stromatolites are found throughout the fossil record, but they became less abundant half a billion years ago, and living stromatolites are rare. The reason for their decline was the rise of multicellular invertebrates such as snails, which grazed on cyanobacteria. These grazers reduced the abundance of stromatolite-forming bacteria. However, for three billion years, cyanobacteria ruled the earth. Their most important legacy is the oxygen in our atmosphere, without which we could not exist. But they left us something else, too. As we shall see, the light-seeking urge that enabled the cyanobacteria to create the ancient stromatolites lives on in today's reef-building corals.

* * *

I am sitting on a deck behind the Foghts' house, perhaps ten feet above the Caribbean. The water beneath me is as clear as the gin in my glass. Trunkfish and parrotfish dart across patches of white sand to peck at the algae that grow on the rocks and corals, then vanish into hidey-holes in the reef. The muted waves whip up miniature whirlwinds of sand that swirl across the sea floor like dust devils across a desert. Comparing a coral reef to a desert is not as farfetched as it seems. In one surprising way, this richly biodiverse ecosystem resembles a desert.

One of the great attractions of tropical seas is their combination of clarity and color. The turquoise waters of the shallows change abruptly to the royal blue of deep water on the far side of the reef. The blue is a reflection of the sky, and the shallows appear turquoise because of the white-sand bottom. But the sky is blue everywhere on earth, so why are temperate and polar seas often green and turbid, instead of blue and clear? The answer is that cool waters teem with tiny green plants called phytoplankton, which are far less abundant in warm, tropical waters. Phytoplankton is food for microscopic animals called zooplankton. Together, these tiny organisms (along with some sediments) create the cloudy, discolored seas to the north and provide food for everything from barnacles to blue whales.

This dearth of plankton is what makes coral reefs resemble deserts; reefs are low in food, just as deserts are low in moisture--and both are requirements for life. But plants and animals abound on reefs, in contrast to the sparseness of life in a desert. How this cornucopia of life thrives in the low-nutrient tropical waters that bathe the coral reefs was a mystery until recently. It was solved when scientists began to understand more about the creatures that create this ecosystem: the corals.

Coral polyps appear to be simple creatures with simple lifestyles. Their bodies consist mainly of tentacles to capture food, a mouth to devour it, and a digestive tract to process it. During the day, polyps usually hunker down in the limestone cups they build to protect themselves. At night, they extend sticky tentacles to capture any zooplankton that float by. But scientists calculated that polyps could obtain only a small fraction of the food they need to survive from the nutrient-poor waters where they live. Like the engineers who proved bumblebees couldn't fly, biologists proved that corals couldn't exist.

Of course, corals do exist, and no one was more aware of that than the scientists who studied them. The logjam was broken in the 1920s when members of a British expedition to the Great Barrier Reef showed that chlorophyll-containing algae lived in the bodies of coral polyps. Some scientists suspected the algae were providing food for the polyps.

Today, we know their suspicions were correct. Like true plants, the symbiotic algae (known as zooxanthellae) that reside in the bodies of coral polyps convert sunlight and carbon dioxide into oxygen, water, and sugars by photosynthesis. And corals, like all animals, require oxygen, water, and sugars to live. Also like other animals, they produce carbon dioxide and ammonia (which is mostly nitrogen) as waste products. The result is a wonderfully efficient system of recycling. The algae supply the polyps with oxygen, water, and sugars; the polyps supply the algae carbon dioxide and a safe haven where they can soak up sunlight. And the ammonia given off by the polyps helps keep the algae healthy in exactly the same way that nitrogen fertilizer helps lawns to flourish. It is, all in all, a very neat arrangement.

The coral polyps of a reef are merely a veneer of life less than an inch thick, supported by a calcium carbonate skeleton. As it turns out, the algae embedded in the coral also enhance calcification, thus playing an important role in the formation of the reef itself. An acre of coral, abetted by the ubiquitous algae in the polyps, can produce forty tons of limestone in a year. Over time, this productivity can create impressive structures. Some Pacific reefs are over four thousand feet thick, and Australia's Great Barrier Reef is nearly thirteen hundred miles long.

Like the blue-green algae that created the ancient stromatolites, the simple, single-cell algae found in the bodies of coral polyps played a key role in forming modern reefs, the most massive structures created by any organism. Algae don't rule the world as they once did, but on the reefs, they still do the heavy lifting.

* * *

On our last day in Bonaire, I join Jim and Martha for a long snorkel down the reef that protects Klein Bonaire, the small island that lies a mile east of Kralendijk. The sea is calm, the sun bright and hot. I jump off the boat, clear my mask, and drift into a coralline world. The reef starts practically on the shore, then drops off steeply to a hundred feet. Orange elephant-ear and purple tube sponges decorate the jumble of corals that covers the wall. Martha, an excellent naturalist, points out leaf coral, wire coral, and mountainous star coral. A hawksbill turtle passes only a few yards in front of my mask, swimming effortlessly with leopard-spotted flippers. Martha follows him into deeper water.

Despite my vow to be more businesslike today, to concentrate on the corals--which I keep reminding myself are the heart of this ecosystem--the fish distract me. And a shark I spot lazing along beneath me is especially distracting. I am determined to identify it. From my bathing suit, I pull out the plastic "Fish-at-a-Glance" card I carry with me. The card has drawings of the common fish of the Netherlands Antilles, from butterfly fish to wrasses. But no sharks. My guess is the artist didn't want to advertise that sharks swim among the Caribbean's tourist-attracting reefs.

The shark is about three or four feet long, a gray torpedo that would be menacing if it paid any attention to me. But it doesn't. This indifference to humans is characteristic of the sharks I've encountered while snorkeling. Only once, in the Bahamas, have I ever seen one act threateningly. A nine-foot nurse shark suddenly appeared behind my wife, Diane, and closed the gap until it was only a few feet from her flippers. I began splashing toward her and yelling underwater. The shark sped away without Diane's ever seeing it, and after she surfaced, she accused me of making the whole thing up.

So even though sharks don't overly concern me, I do believe in keeping an eye on them. And it is only when this one lounges away from the reef, still unidentified, and fades away into the blue smoke of deep water that I focus on the myriad other fish that surround me. Bright, colorful shapes flit around the reef, and as usual, I forget my vow to pay attention to the corals.

A cloud of silvery palometas materializes over the reef and engulfs me. For years, I scoured Florida's sun-blasted flats, trying in vain to catch the palometa's larger cousin, the permit. The permits apparently passed on their low opinion of my fishing prowess to these palometas, because they show absolutely no fear. They swim unconcernedly within inches of my mask before vanishing as suddenly as they appeared.

The current carries me over the heart of the reef. Soon, two French angelfish, perhaps the most spectacular reef species in the Caribbean, join me. They float along a few feet below me and slightly to my left, giving me a perfect view. They are discus shaped, maybe a foot long. One of them seems almost as interested in me as I am in it, tilting itself in the water to watch me with an eerie, yellow-ringed eye. Every scale on its midsection is blue with a yellow edge. The whole fish resembles a dark cloth sprinkled with gold dust. And like an Escher drawing, the colors seem to metamorphose, changing from blue to yellow and blue, then back to blue.

When we reach deeper water, the angelfish scoot back to safety. A trio of barracudas hangs motionless in the blue stillness beyond. I turn and swim toward the reef.

Shimmering schools of black-and-yellow sergeant majors swim leisurely over the dark reef. I spot butterfly fish, filefish, and trunkfish; damselfish, triggerfish, and parrotfish; and several species of blue-and-yellow-streaked grunts. And while I haven't seen any today, I've often spotted moray eels and groupers on this part of the reef.

In fact, the sheer number of species found on coral reefs is the most striking thing about this ecosystem. Efficient recycling can explain the reefs' high biomass, but it does not explain the great diversity of life. It is a problem that has long engaged ecologists. And though theories abound, none is widely accepted. According to E. O. Wilson, the Harvard biologist, "The cause of tropical preeminence [in biodiversity] poses one of the great theoretical problems of evolutionary biology."

Fortunately, we can try to understand and protect this ecosystem without solving the problem. It is clear that, in one way or another, virtually every organism found here depends on the reef. The corals provide shelter and food for a variety of invertebrates and fish, from sea stars to sea urchins, from butterfly fish to damselfish. More importantly, the reef provides a cultch to which sponges, sea fans, and many species of algae can attach themselves. These in turn provide food for everything from snails to parrotfish. The jumble of corals that makes up a reef also provides niches and crevices that harbor creatures as large as moray eels and as small as bacteria and filamentous algae. Clearly, the first step in protecting a reef ecosystem is to protect the corals.

Just before I reach the boat, I dive to get a closer look at a large, brown lump of boulder coral that rests on the sea floor among star corals and assorted gorgonians. Its surface is covered with thousands of small blisters, each of which is a coral polyp with its tentacles retracted. Come nightfall, when the zooplankton begin to rise, the blisters will open and tiny tentacles will unfurl and grab anything that comes within reach.

Some divers never get close enough to a coral head to see the tiny creatures that created it. To them, reefs appear monolithic, stable, and not in much need of protection. But appearances are deceiving. In truth, this ecosystem is balanced on a knife edge, and even small changes in the environment can produce disastrous effects.

Consider, for example, water temperature. Corals are found in waters with temperatures of sixty-four to ninety-seven degrees Fahrenheit, but they thrive only in seas where the mean temperature is between seventy-four and seventy-eight degrees, which is why reefs exist only in tropical waters. Unusually high or low temperatures can damage corals and sometimes kill them.

Corals are also sensitive to light, storms, predator irruptions, dynamite, anchors, cyanide, water salinity, sediments, and, most importantly, sea levels. Corals can survive only a few hours out of the water, so declining sea levels can turn a flourishing coral reef into a lifeless lump of limestone. The hills in the 13,500-acre Washington-Slagbaai National Park in the northeast corner of Bonaire are fossilized limestone terraces formed by living corals when sea levels were higher.

Rising sea levels usually--but not always--treat corals more kindly. Reef-building corals, like the boulder coral I inspected, are colonies composed of hundreds or thousands of polyps, each of which can divide by a process known as budding and produce another polyp. Each polyp creates and occupies its own calcium carbonate cup, called a corallite. However, part of the polyp protrudes above the lip of the cup and connects to its neighbors, creating a mat of living tissue that coats the surface of the coral colony. The mat is invisible because it is transparent, and it is covered with a thin film of mucus, which makes it sticky to the touch.

As the polyps, assisted by their resident algae, continue to secrete calcium carbonate, the coral skeleton grows upward and outward. To keep up, the polyps must periodically lay down a new base plate and move toward the surface. This is a painfully slow process. Still, it is fast enough to allow a reef to keep up with normal rises in sea level. But if the sea rises too rapidly, the reef can "drown." This occurs when the photosynthetic algae in the coral polyps get too little sunlight. The algae then become less productive and eventually die.

This is the beginning of the end of the reef. Although some deepwater corals survive without zooxanthellae, reef-building corals do not thrive without friendly algae to feed them and help them build their protective skeletons.

A rapid increase in sea levels would drive a stake through the heart of the world's reefs.

* * *

Kalli De Meyer is the tanned, youthful-looking manager of Bonaire Marine Park. She is a native of foggy London but seems quite at home on this sun-drenched island. Kalli has degrees in marine biology and oceanography and a clipped, businesslike British accent. She is aware that she runs one of North America's most successful sanctuaries, and she sometimes gives talks to representatives of other countries about how to establish and maintain marine parks.

Kalli knows she has inherited a dream sanctuary, an intact ecosystem that was protected before any significant damage was done to it. Because its rules were (and are) strict and rigorously enforced, the park has suffered little degradation in the years since it was established. The dynamite and cyanide fishing that has devastated many Pacific reefs has never been a problem here. And since the park funds itself by charging each diver a ten-dollar yearly admission fee, it is in no danger of becoming what Kalli calls a "paper park," a sanctuary that exists in name only, as is sometimes the case in the Caribbean.

"Education, research, and enforcement are what marine park management is all about," says Kalli. "No one comes to Bonaire to trash a reef. If damage is caused, it is most often through simple ignorance of the fragility of reef environments. And trying to run a marine park without research and monitoring is like trying to drive blindfolded." The third element--enforcement--should "kick in with the small percentage of users with whom education fails to make any impact."

Despite Kalli's efforts, the park faces threats. One is its ever-increasing popularity. When it was established in 1979, fewer than five thousand scuba divers used the park; by 1994, the number was up to twenty-five thousand and still growing. The park is, Kalli says, "approaching what we believe to be the carrying capacity of the reefs in terms of diver visitation." To combat this problem, she is trying to convince the local government to diversify Bonaire's tourist base.

Regardless of the outcome of her lobbying, the park faces other threats over which Kalli has little control. Sediment created by soil erosion from coastal-zone development can smother corals every bit as effectively as overgrown algae. Many marine biologists believe that this is the biggest problem facing reefs in the rapidly developing South Pacific--bigger even than dynamite and cyanide fishing. So far, though, sedimentation hasn't been a problem on Bonaire's reefs.

But even Bonaire could not escape coral bleaching, a widespread phenomenon that hit Caribbean and Pacific reefs in the 1980s and 1990s. Bleaching occurs when corals expel their zooxanthellae in response to an increase in water temperature or some other stress. Without their internal algae, the transparent corals appear white, the color of their limestone skeletons. And prolonged bleaching will eventually kill corals.

The tongue of warm water called El Niño has recently caused substantial bleaching of the Great Barrier Reef. Kalli says that when water temperatures on Bonaire's reefs exceed 85.1 degrees Fahrenheit, bleaching occurs. This has happened twice at the park, once in 1990 and again in 1995. However, few corals died, and I saw no aftereffects from bleaching when I was there in 1994 and 1997. No one knows for sure why Bonaire Marine Park escaped the devastating coral mortality that followed bleaching elsewhere in the Caribbean, but the immaculate condition of its reefs probably didn't hurt.

Perhaps the biggest problem the park faces is one that looms over every coral reef in the world: global warming. Since the Industrial Revolution, carbon dioxide in the atmosphere has increased from 280 to 360 parts per million. Carbon dioxide traps the sun's heat, and the Environmental Protection Agency reports that the earth's mean surface temperature rose about one degree Fahrenheit in the last century. In addition to causing bleaching, high water temperatures melt glaciers and other ice in the polar regions, which raises sea levels--four to ten inches in the last century alone.

In the coming century, sea levels are expected to rise even faster. Among the doomsday and the don't-worry numbers that swirl about this issue, the best estimate is probably the middle-of-the-road figure used by the EPA. It predicts that sea levels will rise thirteen inches in the next hundred years. The question that concerns the managers of the world's tropical marine parks is, Can reef-building corals keep up with this increase?

Some corals will have no problem. Staghorn coral, one of the major components of Bonaire's reefs, can grow up to 10 inches a year, fast enough to keep up with rising seas in all but the most catastrophic scenarios. But star coral, which is also important in Caribbean reefs, grows more slowly, only about 0.2 to 0.4 inch per year. Even so, that's 20 or more inches per century, a growth rate that should enable it to keep pace with rising sea levels.

Of course, all of this is guesswork. Nobody really knows how fast sea levels will rise, and nobody knows for sure how the reefs will react. And though a few scientists predict disaster, I'm betting on the reefs--and on Kalli De Meyer and the rest of us.

Sea levels have waxed and waned thousands of times since the first stromatolitic reefs rose in Precambrian waters, and stromatolites are still around today. The precursors of today's corals began building limestone reefs 500 million years ago. Since then, sea levels have fluctuated hundreds of feet, and reefs of one sort or another still exist. With that kind of record, it's possible to get complacent about the future of coral reefs.

Such complacency, however, would be misplaced. The fossil record shows that coral reefs have vanished from the earth several times, only to reappear a few million years later. Nobody knows what caused the demise of the reefs, but climate changes probably played a role. Which brings us back to Kalli De Meyer--and to the rest of us.

So far, Bonaire Marine Park's efforts to preserve the reefs--eliminating anchoring, stopping spearfishing and coral collecting, and instituting a don't-touch-the-reef policy--have been wildly successful, as has Kalli's emphasis on education, research, and enforcement. The remaining threats--sedimentation due to soil runoff, pollution, warming waters, and rising sea levels--are largely outside the park's control. And that's where the rest of us come in.

We must convince politicians to properly manage coastal-zone development; we must insist on adequate sewage treatment systems, and be willing to pay for them; and we must reduce the amount of carbon dioxide we spew into the air.

Sanctuaries are islands of hope surrounded by the rest of us. And ultimately, it is we who are responsible for their survival.