The Flight of the Iguana (20 page)

Meanwhile, as hordes of starfish turned up in those far-flung places and new pockets of infestation appeared on the Great Barrier Reef, Green Island was left alone. The journal
Science
announced that “recovery is reported to have already begun; the island was free of starfish in 1968, and new colonies of four coral genera had become established.”

See there, said the optimists. These fluctuations of
A. planci
population are merely a natural phenomenon, kept within bounds by the internal checks and balances of the reef community. One shouldn't get too excited, they said. Most of all, one shouldn't intervene in these natural cycles, on the ever-precarious basis of good intentions and incomplete knowledge. An ecosystem as complex as a coral reef, and as stable, can bloody well take care of itself.

Or so went the hopeful assertion.

But it wasn't that simple. In 1979
A. planci
came back to Green Island.

Robert Endean, an Australian biologist who has been a leading authority on crown-of-thorns starfish for the past two decades, dived the Green Island reef that year and found that sixty percent of the coral had been killed—recently. He estimated the current
A. planci
population at 350,000. Since then, says Endean, things have gotten still worse. This time
A. planci
is not only killing the plate-coral and the branching-coral species. It is also killing the great massive brain-coral colonies, some of which are hundreds of years old.

•   •   •

There is a rough pattern to all those centers of starfish infestation that erupted across the Pacific during the 1960s and '70s. The pattern is that
A. planci
appears in great numbers, generally, where
Homo sapiens
has also appeared in great numbers. The earliest outbreaks of the starfish plague have been focused mainly on reefs near those coasts and islands with considerable modern human settlement. This is the circumstantial evidence that points an accusing finger at humankind.

What could the etiology be? What human actions could conceivably bring on a cataclysmic proliferation of starfish?

The most logical guess is that we humans might somehow have released
A. planci
from the pressure normally exerted upon it by predators. Those missing predators might have fed on the eggs of the starfish, or on the free-swimming larval forms, or even perhaps (improbable as it seems) on the imposing adults, two feet across and armed with poison spines. Possibly there was a constellation of predators who fed variously on all three stages, thus keeping
A. planci
trimmed down to a sparse population, a mere half dozen for every square mile of reef. Possibly. But no one knows.

How might humanity have eliminated the predators? With industrial
pollution? With insecticides, running off in erosional waters from the land? By dredging and blasting operations in crucial zones of coral? All of these notions have been mentioned in the scientific debate, and none of them seems very likely. But no one knows.

Robert Endean, speaking by phone from his office in Brisbane, offers an alternative view. He suspects that the critical stage at which
A. planci
suffers predation (or in the more recent situation, the stage at which it
should
suffer predation but doesn't) is neither as eggs nor as larvae nor as full-grown adults. Instead, Endean posits that the post-larval juveniles might be the preyed-upon form. At this stage the animal has reached its adult shape but not its adult size. It is a miniature starfish, just an inch or a few inches across, a convenient morsel for a fish or a large snail, and the long potent spines have not yet developed. In the juvenile stage, Endean says,
A. planci
could be quite vulnerable to a whole constellation of predators, species such as are native to coral reefs in an undisturbed state. Among those predators would be the giant triton,
Charonia tritonis,
a snail-like gastropod that grows twenty inches long and has been seen feeding on crown-of-thorns starfish. Also included might be such fishes as the hump-headed wrasse, the spotted toado, several types of triggerfish, groupers, coral trout, and a number of other reef-dwelling species. Taken together, the pressure of predation by these animals upon
A. planci
in its juvenile and small-adult stages might be just adequate to keep the starfish at low population levels. Taken away, those animals by their absence might explain the
A. planci
plague.

And, according to Dr. Endean, precisely those animals
have
been taken away by human activities in places like Green Island. Beginning back in the 1950s, the giant triton has been collected by the tens of thousands for its beautiful shell, which was sold to tourists as a souvenir. The various predatory reef fish have been drastically reduced by spear-fishing divers and commercial fishermen.
Some of those predators were probably specific, focusing on
A. planci
to the exclusion of other prey. Some were no doubt generalists, eating juvenile
A. planci
among other things. One result of their combined disappearance, suggests Endean, is a population explosion among starfish.

•   •   •

But what about simplicity versus complexity? What about stability versus fragility?

A tropical rainforest is undeniably complex, and presumably therefore quite stable. But stability is a relative value—relative to the magnitude of the disturbance inflicted. No ecosystem is invulnerable. And no ecosystem is immune to disturbances of the magnitude that humankind often inflicts. If you remove the canopy trees from a large area of the richest Amazon jungle, chances are that you
will
destroy the ecosystem there, for a very long time indeed, if not permanently. Likewise if you take a heavy enough toll—a subtle toll, maybe, but a critical one—on the complex community of a coral reef.

An ecologist named Ramón Margalef has written: “A strong exploitation of very mature ecosystems, like tropical forests or coral reefs, may produce a total collapse of a rich organization. In such stable biotopes, nature is not prepared for a step backward. Man has to be very careful in dealing with systems of high maturity.”

Certainly the Great Barrier Reef is one of our planet's most mature ecosystems. And if it dies, under a crown of thorns, there may be no prospect of resurrection.

One Family's Quest Through the Strata of Time

In an inconspicuous brick building on the outskirts of the village of Holzmaden, in southern Germany, is a large female animal caught in the act of giving birth. The moment is frozen precisely, rather poignantly, as though by the snap of a shutter. The image is stark, nearly flat, black and white. This isn't a photograph. It is a natural bas-relief executed in marine mud and bone and the awesome pressures of time and accreting rock—in other words, a fossil. Almost 200 million years old but preserved in all delicate filigree, like a maple leaf pressed lovingly in a book by the hand of a child who has long since grown old and wizened, this particular fossil is different from any other you are ever likely to see. The anatomy is unusual. The specimen is whole, intact, and breathtakingly vivid. The tableau contains a double share of silent drama, since in this case the moment of birth was also, evidently, the moment of death. Altogether it may be one of the world's most eloquent fossils. The animal is called
Stenopterygius crassicostatus.
The inconspicuous building is called Museum Hauff.

This maternal beast is an ichthyosaur, a marine reptile from the age of the dinosaurs. She was not herself a dinosaur; she was something else, something other, something more than a little
oxymoronic: a fish-like reptile that breathed air but lived all her life in the sea, shaped by evolution to the same body form and the same ecological role as a dolphin, all those millions of years before dolphinhood was reinvented by the mammals. She died at sea and was buried in sea-bottom mud, very gently, with her one newborn beside her and five embryos still in her abdomen. The cause of death can't be known. Possibly it was childbirth itself. Finally in the year we call 1948 she was pried up from a shale quarry, right there at Holzmaden, and teased out of her slab by the painstaking efforts of two men, both of them named Bernhard Hauff. They were father and son, founder and first heir of a quiet dynasty that has supplied the twentieth century with ichthyosaurs.

“These ichthyosaurs were animals that evoluted very specially for water life,” says Rolf Bernhard Hauff, grandson in the same line and now director of the museum and its renowned fossil-preparation workshop. The young Herr Hauff is handsome and genial, no archetype of dour fossiliferous stodginess as one might expect but a contemporary man, dressed this morning in jeans and a scarlet sweatshirt. He is conducting a tour in English for a group of American teenagers, high school kids from a nearby Air Force base, and struggling amiably toward a compromise with the attention span of his audience, the scientific complexity of his subject, and the language. His English is good but imperfect and the word he wants is
evolved.

These ichthyosaurs had indeed evolved very specially for life in the ancient seas. The fossil is the proof. It tells of an animal twelve feet in length, weighing perhaps half a ton, with a strikingly large eye socket that suggests a creature dependent on keen sight, and a long toothy beak suited for preying upon small fish and squid. It tells of streamlining, and the transformation of legs to flippers, and a powerful shark-like tail, and more.

Herr Hauff points to the rib cage of this great gravid
Stenopterygius,
hung in its gray slab on one museum wall. Five miniature
skulls, five little bodies, show clearly between the ribs. “And inside we see very small ichthyosaurs. And these ichthyosaurs, we know then, they bring forth very small babies. They give live birth. Not like an alligator or a turtle, eh?, that lays eggs on a beach. And so we know that the ichthyosaurs were
very
well adapted to life in the sea.” A live-bearing sea reptile was one that
never
needed to go ashore, because its newborn could swim up to the surface for air, whereas an egg laid on the sea bottom would, literally, drown—this being an important point scientifically, if not one to draw gasps from school kids. Herr Hauff keeps his tour brisk and palatable, moving quickly across matters of evidence—captured in these extraordinary fossils—that have given the Hauff collection, and the Hauff workshop, a revered place in paleontology for the past ninety years.

He is good with this crowd of distracted, hormonal adolescents. He smiles, he looks them in the eyes, he makes jokes and quizzes them Socratically. He knows that they might hear half of what he tells them, and retain a twentieth overnight—or maybe they will retain a tenth, if he gets them involved. Maybe in a few years one or two of them will remember that once, on an escape from the classroom, they visited an astounding, tiny museum in some little town of south Germany. Herr Hauff cares about that possibility. He avowedly views his own efforts, his family's ancestral mission, as directed not just toward science but also toward the public. Ichthyosaurs, he seems to believe, are a miracle that belongs to everyone.

He leans over a smaller specimen in a tabletop case. “This is the backbone. And this black line is not painted here,” he says. Flattened almost to two dimensions on its bed of gray shale, the skeleton is surrounded by a smooth coal-dark silhouette: the full outline of a body, left behind by chemical transformation of the animal's skin. That outline is a rarity, an artifact as improbable as the face in Veronica's veil, with scientific significance that a modest man like Rolf Hauff could scarcely exaggerate. It establishes
that ichthyosaurs had almost precisely the same shape as dolphins, with a dorsal fin and a tall upper horn on the caudal fin that do not show up in the skeleton. “We find this only with very careful preparation. Soft-body parts preserved so good, we find only here in all the world. This takes
very
careful preparation. Almost a year to prepare one specimen.”

The tradition of fine craftsmanship in the Hauff workshop is only part of what has made these fossils so useful to science, and so beautiful. The other part involves geological accident. This area of southern Germany in which Holzmaden lies—just forty kilometers east of Stuttgart, at the base of a hilly upthrust known as the Swabian Alb—once lay at the bottom of a shallow sea. During the Jurassic period of Earth history, roughly between 190 and 136 million years ago, that inland sea covered a large portion of what is now western Europe. In the Holzmaden area, which was some distance off the coast, fine-grain muddy sediments were laid down upon the sea bottom, compressing and hardening finally into rock, and in the process entombing dead marine animals wherever the bodies fell. The sea bottom here was especially stable, undisturbed by currents, poor in oxygen, so that carcasses settling into the mud were often preserved free of dismemberment or rot. Laced richly with organic material (not just ichthyosaur bodies but various marine reptiles, fish, mollusks, and an abundance of other invertebrates), the hardening layers of mud eventually became strata of oil shale. Those dark carboniferous strata are known by geologists as the Black Jurassic. The sea retreated, the Swabian Alb was uplifted by pressures along the Earth's crust, and erosion gradually stripped away other strata formed after the shale. Millions of years later, Rolf Hauff's great-grandfather came to Holzmaden as an industrial chemist, with the notion of exploiting that oil shale. But his son, the founding grandfather of the fossil operation, was more interested in the shale as a mausoleum of vanished reptiles than for its sheer bitumen content.