18 THE BOUNDING MAIN
《万物简史英文版》章节: 18 THE BOUNDING MAIN,宠文网网友提供全文无弹窗免费在线阅读。!
Water is everywhere. A potato is 80 percent water, a cow 74 percent, a bacterium 75percent. A tomato, at 95 percent, is little but water. Even humans are 65 percent water,making us more liquid than solid by a margin of almost two to one. Water is strange stuff. It isformless and transparent, and yet we long to be beside it. It has no taste and yet we love thetaste of it. We will travel great distances and pay small fortunes to see it in sunshine. Andeven though we know it is dangerous and drowns tens of thousands of people every year, wecan’t wait to frolic in it.
Because water is so ubiquitous we tend to overlook what an extraordinary substance it is.
Almost nothing about it can be used to make reliable predictions about the properties of otherliquids and vice versa. If you knew nothing of water and based your assumptions on thebehavior of compounds most chemically akin to it—hydrogen selenide or hydrogen sulphidenotably—you would expect it to boil at minus 135 degrees Fahrenheit and to be a gas at roomtemperature.
Most liquids when chilled contract by about 10 percent. Water does too, but only down to apoint. Once it is within whispering distance of freezing, it begins—perversely, beguilingly,extremely improbably—to expand. By the time it is solid, it is almost a tenth morevoluminous than it was before. Because it expands, ice floats on water—“an utterly bizarreproperty,” according to John Gribbin. If it lacked this splendid waywardness, ice would sink,and lakes and oceans would freeze from the bottom up. Without surface ice to hold heat in,the water’s warmth would radiate away, leaving it even chillier and creating yet more ice.
Soon even the oceans would freeze and almost certainly stay that way for a very long time,probably forever—hardly the conditions to nurture life. Thankfully for us, water seemsunaware of the rules of chemistry or laws of physics.
Everyone knows that water’s chemical formula is H2O, which means that it consists of onelargish oxygen atom with two smaller hydrogen atoms attached to it. The hydrogen atomscling fiercely to their oxygen host, but also make casual bonds with other water molecules.
The nature of a water molecule means that it engages in a kind of dance with other watermolecules, briefly pairing and then moving on, like the ever-changing partners in a quadrille,to use Robert Kunzig’s nice phrase. A glass of water may not appear terribly lively, but everymolecule in it is changing partners billions of times a second. That’s why water moleculesstick together to form bodies like puddles and lakes, but not so tightly that they can’t be easily separated as when, for instance, you dive into a pool of them. At any given moment only 15percent of them are actually touching.
In one sense the bond is very strong—it is why water molecules can flow uphill whensiphoned and why water droplets on a car hood show such a singular determination to beadwith their partners. It is also why water has surface tension. The molecules at the surface areattracted more powerfully to the like molecules beneath and beside them than to the airmolecules above. This creates a sort of membrane strong enough to support insects andskipping stones. It is what gives the sting to a belly flop.
I hardly need point out that we would be lost without it. Deprived of water, the human bodyrapidly falls apart. Within days, the lips vanish “as if amputated, the gums blacken, the nosewithers to half its length, and the skin so contracts around the eyes as to prevent blinking.”
Water is so vital to us that it is easy to overlook that all but the smallest fraction of the wateron Earth is poisonous to us—deadly poisonous—because of the salts within it.
We need salt to live, but only in very small amounts, and seawater contains way more—about seventy times more—salt than we can safely metabolize. A typical liter of seawater willcontain only about 2.5 teaspoons of common salt—the kind we sprinkle on food—but muchlarger amounts of other elements, compounds, and other dissolved solids, which arecollectively known as salts. The proportions of these salts and minerals in our tissues isuncannily similar to seawater—we sweat and cry seawater, as Margulis and Sagan have putit—but curiously we cannot tolerate them as an input. Take a lot of salt into your body andyour metabolism very quickly goes into crisis. From every cell, water molecules rush off likeso many volunteer firemen to try to dilute and carry off the sudden intake of salt. This leavesthe cells dangerously short of the water they need to carry out their normal functions. Theybecome, in a word, dehydrated. In extreme situations, dehydration will lead to seizures,unconsciousness, and brain damage. Meanwhile, the overworked blood cells carry the salt tothe kidneys, which eventually become overwhelmed and shut down. Without functioningkidneys you die. That is why we don’t drink seawater.
There are 320 million cubic miles of water on Earth and that is all we’re ever going to get.
The system is closed: practically speaking, nothing can be added or subtracted. The water youdrink has been around doing its job since the Earth was young. By 3.8 billion years ago, theoceans had (at least more or less) achieved their present volumes.
The water realm is known as the hydrosphere and it is overwhelmingly oceanic. Ninety-seven percent of all the water on Earth is in the seas, the greater part of it in the Pacific, whichcovers half the planet and is bigger than all the landmasses put together. Altogether thePacific holds just over half of all the ocean water (51.6 percent to be precise); the Atlantic has23.6 percent and the Indian Ocean 21.2 percent, leaving just 3.6 percent to be accounted forby all the other seas. The average depth of the ocean is 2.4 miles, with the Pacific on averageabout a thousand feet deeper than the Atlantic and Indian Oceans. Altogether 60 percent ofthe planet’s surface is ocean more than a mile deep. As Philip Ball notes, we would better callour planet not Earth but Water.
Of the 3 percent of Earth’s water that is fresh, most exists as ice sheets. Only the tiniestamount—0.036 percent—is found in lakes, rivers, and reservoirs, and an even smaller part—just 0.001 percent—exists in clouds or as vapor. Nearly 90 percent of the planet’s ice is inAntarctica, and most of the rest is in Greenland. Go to the South Pole and you will bestanding on nearly two miles of ice, at the North Pole just fifteen feet of it. Antarctica alone has six million cubic miles of ice—enough to raise the oceans by a height of two hundred feetif it all melted. But if all the water in the atmosphere fell as rain, evenly everywhere, theoceans would deepen by only an inch.
Sea level, incidentally, is an almost entirely notional concept. Seas are not level at all.
Tides, winds, the Coriolis force, and other effects alter water levels considerably from oneocean to another and within oceans as well. The Pacific is about a foot and a half higher alongits western edge—a consequence of the centrifugal force created by the Earth’s spin. Just aswhen you pull on a tub of water the water tends to flow toward the other end, as if reluctant tocome with you, so the eastward spin of Earth piles water up against the ocean’s westernmargins.
Considering the age-old importance of the seas to us, it is striking how long it took theworld to take a scientific interest in them. Until well into the nineteenth century most of whatwas known about the oceans was based on what washed ashore or came up in fishing nets,and nearly all that was written was based more on anecdote and supposition than on physicalevidence. In the 1830s, the British naturalist Edward Forbes surveyed ocean beds throughoutthe Atlantic and Mediterranean and declared that there was no life at all in the seas below2,000 feet. It seemed a reasonable assumption. There was no light at that depth, so no plantlife, and the pressures of water at such depths were known to be extreme. So it came assomething of a surprise when, in 1860, one of the first transatlantic telegraph cables washauled up for repairs from more than two miles down, and it was found to be thicklyencrusted with corals, clams, and other living detritus.
The first really organized investigation of the seas didn’t come until 1872, when a jointexpedition between the British Museum, the Royal Society, and the British government setforth from Portsmouth on a former warship called HMS Challenger. For three and a halfyears they sailed the world, sampling waters, netting fish, and hauling a dredge throughsediments. It was evidently dreary work. Out of a complement of 240 scientists and crew, onein four jumped ship and eight more died or went mad—“driven to distraction by the mind-numbing routine of years of dredging” in the words of the historian Samantha Weinberg. Butthey sailed across almost 70,000 nautical miles of sea, collected over 4,700 new species ofmarine organisms, gathered enough information to create a fifty-volume report (which tooknineteen years to put together), and gave the world the name of a new scientific discipline:
oceanography. They also discovered, by means of depth measurements, that there appeared tobe submerged mountains in the mid-Atlantic, prompting some excited observers to speculatethat they had found the lost continent of Atlantis.
Because the institutional world mostly ignored the seas, it fell to devoted—and veryoccasional—amateurs to tell us what was down there. Modern deep-water exploration beginswith Charles William Beebe and Otis Barton in 1930. Although they were equal partners, themore colorful Beebe has always received far more written attention. Born in 1877 into a well-to-do family in New York City, Beebe studied zoology at Columbia University, then took ajob as a birdkeeper at the New York Zoological Society. Tiring of that, he decided to adoptthe life of an adventurer and for the next quarter century traveled extensively through Asiaand South America with a succession of attractive female assistants whose jobs wereinventively described as “historian and technicist” or “assistant in fish problems.” Hesupported these endeavors with a succession of popular books with titles like Edge of theJungle and Jungle Days, though he also produced some respectable books on wildlife andornithology.
In the mid-1920s, on a trip to the Galápagos Islands, he discovered “the delights ofdangling,” as he described deep-sea diving. Soon afterward he teamed up with Barton, whocame from an even wealthier family, had also attended Columbia, and also longed foradventure. Although Beebe nearly always gets the credit, it was in fact Barton who designedthe first bathysphere (from the Greek word for “deep”) and funded the $12,000 cost of itsconstruction. It was a tiny and necessarily robust chamber, made of cast iron 1.5 inches thickand with two small portholes containing quartz blocks three inches thick. It held two men, butonly if they were prepared to become extremely well acquainted. Even by the standards of theage, the technology was unsophisticated. The sphere had no maneuverability—it simply hungon the end of a long cable—and only the most primitive breathing system: to neutralize theirown carbon dioxide they set out open cans of soda lime, and to absorb moisture they opened asmall tub of calcium chloride, over which they sometimes waved palm fronds to encouragechemical reactions.
But the nameless little bathysphere did the job it was intended to do. On the first dive, inJune 1930 in the Bahamas, Barton and Beebe set a world record by descending to 600 feet. By1934, they had pushed the record to 3,028 feet, where it would stay until after the war. Bartonwas confident the device was safe to a depth of 4,500 feet, though the strain on every bolt andrivet was audibly evident with each fathom they descended. At any depth, it was brave andrisky work. At 3,000 feet, their little porthole was subjected to nineteen tons of pressure persquare inch. Death at such a depth would have been instantaneous, as Beebe never failed toobserve in his many books, articles, and radio broadcasts. Their main concern, however, wasthat the shipboard winch, straining to hold on to a metal ball and two tons of steel cable,would snap and send the two men plunging to the seafloor. In such an event, nothing couldhave saved them.
The one thing their descents didn’t produce was a great deal of worthwhile science.
Although they encountered many creatures that had not been seen before, the limits ofvisibility and the fact that neither of the intrepid aquanauts was a trained oceanographer meantthey often weren’t able to describe their findings in the kind of detail that real scientistscraved. The sphere didn’t carry an external light, merely a 250-watt bulb they could hold upto the window, but the water below five hundred feet was practically impenetrable anyway,and they were peering into it through three inches of quartz, so anything they hoped to viewwould have to be nearly as interested in them as they were in it. About all they could report, inconsequence, was that there were a lot of strange things down there. On one dive in 1934,Beebe was startled to spy a giant serpent “more than twenty feet long and very wide.” Itpassed too swiftly to be more than a shadow. Whatever it was, nothing like it has been seenby anyone since. Because of such vagueness their reports were generally ignored byacademics.
After their record-breaking descent of 1934, Beebe lost interest in diving and moved on toother adventures, but Barton persevered. To his credit, Beebe always told anyone who askedthat Barton was the real brains behind the enterprise, but Barton seemed unable to step fromthe shadows. He, too, wrote thrilling accounts of their underwater adventures and even starredin a Hollywood movie called Titans of the Deep, featuring a bathysphere and many excitingand largely fictionalized encounters with aggressive giant squid and the like. He evenadvertised Camel cigarettes (“They don’t give me jittery nerves”). In 1948 he increased thedepth record by 50 percent, with a dive to 4,500 feet in the Pacific Ocean near California, butthe world seemed determined to overlook him. One newspaper reviewer of Titans of the Deepactually thought the star of the film was Beebe. Nowadays, Barton is lucky to get a mention.
At all events, he was about to be comprehensively eclipsed by a father-and-son team fromSwitzerland, Auguste and Jacques Piccard, who were designing a new type of probe called abathyscaphe (meaning “deep boat”). Christened Trieste, after the Italian city in which it wasbuilt, the new device maneuvered independently, though it did little more than just go up anddown. On one of its first dives, in early 1954, it descended to below 13,287 feet, nearly threetimes Barton’s record-breaking dive of six years earlier. But deep-sea dives required a greatdeal of costly support, and the Piccards were gradually going broke.
In 1958, they did a deal with the U.S. Navy, which gave the Navy ownership but left themin control. Now flush with funds, the Piccards rebuilt the vessel, giving it walls five inchesthick and shrinking the windows to just two inches in diameter—little more than peepholes.
But it was now strong enough to withstand truly enormous pressures, and in January 1960Jacques Piccard and Lieutenant Don Walsh of the U.S. Navy sank slowly to the bottom of theocean’s deepest canyon, the Mariana Trench, some 250 miles off Guam in the western Pacific(and discovered, not incidentally, by Harry Hess with his fathometer). It took just under fourhours to fall 35,820 feet, or almost seven miles. Although the pressure at that depth wasnearly 17,000 pounds per square inch, they noticed with surprise that they disturbed a bottom-dwelling flatfish just as they touched down. They had no facilities for taking photographs, sothere is no visual record of the event.
After just twenty minutes at the world’s deepest point, they returned to the surface. It wasthe only occasion on which human beings have gone so deep.
Forty years later, the question that naturally occurs is: Why has no one gone back since? Tobegin with, further dives were vigorously opposed by Vice Admiral Hyman G. Rickover, aman who had a lively temperament, forceful views, and, most pertinently, control of thedepartmental checkbook. He thought underwater exploration a waste of resources and pointedout that the Navy was not a research institute. The nation, moreover, was about to becomefully preoccupied with space travel and the quest to send a man to the Moon, which madedeep sea investigations seem unimportant and rather old-fashioned. But the decisiveconsideration was that the Trieste descent didn’t actually achieve much. As a Navy officialexplained years later: “We didn’t learn a hell of a lot from it, other than that we could do it.
Why do it again?” It was, in short, a long way to go to find a flatfish, and expensive too.
Repeating the exercise today, it has been estimated, would cost at least $100 million.
When underwater researchers realized that the Navy had no intention of pursuing apromised exploration program, there was a pained outcry. Partly to placate its critics, theNavy provided funding for a more advanced submersible, to be operated by the Woods HoleOceanographic Institution of Massachusetts. Called Alvin, in somewhat contracted honor ofthe oceanographer Allyn C. Vine, it would be a fully maneuverable minisubmarine, though itwouldn’t go anywhere near as deep as the Trieste. There was just one problem: the designerscouldn’t find anyone willing to build it. According to William J. Broad in The UniverseBelow: “No big company like General Dynamics, which made submarines for the Navy,wanted to take on a project disparaged by both the Bureau of Ships and Admiral Rickover, thegods of naval patronage.” Eventually, not to say improbably, Alvin was constructed byGeneral Mills, the food company, at a factory where it made the machines to producebreakfast cereals.
As for what else was down there, people really had very little idea. Well into the 1950s, thebest maps available to oceanographers were overwhelmingly based on a little detail fromscattered surveys going back to 1929 grafted onto, essentially an ocean of guesswork. The Navy had excellent charts with which to guide submarines through canyons and aroundguyots, but it didn’t wish such information to fall into Soviet hands, so it kept its knowledgeclassified. Academics therefore had to make do with sketchy and antiquated surveys or relyon hopeful surmise. Even today our knowledge of the ocean floors remains remarkably lowresolution. If you look at the Moon with a standard backyard telescope you will seesubstantial craters—Fracastorious, Blancanus, Zach, Planck, and many others familiar to anylunar scientist—that would be unknown if they were on our own ocean floors. We have bettermaps of Mars than we do of our own seabeds.
At the surface level, investigative techniques have also been a trifle ad hoc. In 1994, thirty-four thousand ice hockey gloves were swept overboard from a Korean cargo ship during astorm in the Pacific. The gloves washed up all over, from Vancouver to Vietnam, helpingoceanographers to trace currents more accurately than they ever had before.
Today Alvin is nearly forty years old, but it still remains America’s premier research vessel.
There are still no submersibles that can go anywhere near the depth of the Mariana Trenchand only five, including Alvin, that can reach the depths of the “abyssal plain”—the deepocean floor—that covers more than half the planet’s surface. A typical submersible costsabout $25,000 a day to operate, so they are hardly dropped into the water on a whim, still lessput to sea in the hope that they will randomly stumble on something of interest. It’s rather asif our firsthand experience of the surface world were based on the work of five guys exploringon garden tractors after dark. According to Robert Kunzig, humans may have scrutinized“perhaps a millionth or a billionth of the sea’s darkness. Maybe less. Maybe much less.”
But oceanographers are nothing if not industrious, and they have made several importantdiscoveries with their limited resources—including, in 1977, one of the most important andstartling biological discoveries of the twentieth century. In that year Alvin found teemingcolonies of large organisms living on and around deep-sea vents off the Galápagos Islands—tube worms over ten feet long, clams a foot wide, shrimps and mussels in profusion,wriggling spaghetti worms. They all owed their existence to vast colonies of bacteria thatwere deriving their energy and sustenance from hydrogen sulfides—compounds profoundlytoxic to surface creatures—that were pouring steadily from the vents. It was a worldindependent of sunlight, oxygen, or anything else normally associated with life. This was aliving system based not on photosynthesis but on chemosynthesis, an arrangement thatbiologists would have dismissed as preposterous had anyone been imaginative enough tosuggest it.
Huge amounts of heat and energy flow from these vents. Two dozen of them together willproduce as much energy as a large power station, and the range of temperatures around themis enormous. The temperature at the point of outflow can be as much as 760 degreesFahrenheit, while a few feet away the water may be only two or three degrees above freezing.
A type of worm called an alvinellid was found living right on the margins, with the watertemperature 140 degrees warmer at its head than at its tail. Before this it had been thought thatno complex organisms could survive in water warmer than about 130 degrees, and here wasone that was surviving warmer temperatures than that and extreme cold to boot. Thediscovery transformed our understanding of the requirements for life.
It also answered one of the great puzzles of oceanography—something that many of usdidn’t realize was a puzzle—namely, why the oceans don’t grow saltier with time. At the riskof stating the obvious, there is a lot of salt in the sea—enough to bury every bit of land on theplanet to a depth of about five hundred feet. Millions of gallons of fresh water evaporate from the ocean daily, leaving all their salts behind, so logically the seas ought to grow more saltywith the passing years, but they don’t. Something takes an amount of salt out of the waterequivalent to the amount being put in. For the longest time, no one could figure out whatcould be responsible for this.
Alvin’s discovery of the deep-sea vents provided the answer. Geophysicists realized that thevents were acting much like the filters in a fish tank. As water is taken down into the crust,salts are stripped from it, and eventually clean water is blown out again through the chimneystacks. The process is not swift—it can take up to ten million years to clean an ocean—but itis marvelously efficient as long as you are not in a hurry.
Perhaps nothing speaks more clearly of our psychological remoteness from the oceandepths than that the main expressed goal for oceanographers during International GeophysicalYear of 1957–58 was to study “the use of ocean depths for the dumping of radioactivewastes.” This wasn’t a secret assignment, you understand, but a proud public boast. In fact,though it wasn’t much publicized, by 1957–58 the dumping of radioactive wastes had alreadybeen going on, with a certain appalling vigor, for over a decade. Since 1946, the United Stateshad been ferrying fifty-five-gallon drums of radioactive gunk out to the Farallon Islands,some thirty miles off the California coast near San Francisco, where it simply threw themoverboard.
It was all quite extraordinarily sloppy. Most of the drums were exactly the sort you seerusting behind gas stations or standing outside factories, with no protective linings of anytype. When they failed to sink, which was usually, Navy gunners riddled them with bullets tolet water in (and, of course, plutonium, uranium, and strontium out). Before it was halted inthe 1990s, the United States had dumped many hundreds of thousands of drums into aboutfifty ocean sites—almost fifty thousand of them in the Farallons alone. But the U.S. was by nomeans alone. Among the other enthusiastic dumpers were Russia, China, Japan, New Zealand,and nearly all the nations of Europe.
And what effect might all this have had on life beneath the seas? Well, little, we hope, butwe actually have no idea. We are astoundingly, sumptuously, radiantly ignorant of lifebeneath the seas. Even the most substantial ocean creatures are often remarkably little knownto us—including the most mighty of them all, the great blue whale, a creature of suchleviathan proportions that (to quote David Attenborough) its “tongue weighs as much as anelephant, its heart is the size of a car and some of its blood vessels are so wide that you couldswim down them.” It is the most gargantuan beast that Earth has yet produced, bigger eventhan the most cumbrous dinosaurs. Yet the lives of blue whales are largely a mystery to us.
Much of the time we have no idea where they are—where they go to breed, for instance, orwhat routes they follow to get there. What little we know of them comes almost entirely fromeavesdropping on their songs, but even these are a mystery. Blue whales will sometimes breakoff a song, then pick it up again at the same spot six months later. Sometimes they strike upwith a new song, which no member can have heard before but which each already knows.
How they do this is not remotely understood. And these are animals that must routinely cometo the surface to breathe.
For animals that need never surface, obscurity can be even more tantalizing. Consider thefabled giant squid. Though nothing on the scale of the blue whale, it is a decidedly substantialanimal, with eyes the size of soccer balls and trailing tentacles that can reach lengths of sixty feet. It weighs nearly a ton and is Earth’s largest invertebrate. If you dumped one in a normalhousehold swimming pool, there wouldn’t be much room for anything else. Yet no scientist—no person as far as we know—has ever seen a giant squid alive. Zoologists have devotedcareers to trying to capture, or just glimpse, living giant squid and have always failed. Theyare known mostly from being washed up on beaches—particularly, for unknown reasons, thebeaches of the South Island of New Zealand. They must exist in large numbers because theyform a central part of the sperm whale’s diet, and sperm whales take a lot of feeding.
1According to one estimate, there could be as many as thirty million species of animalsliving in the sea, most still undiscovered. The first hint of how abundant life is in the deepseas didn’t come until as recently as the 1960s with the invention of the epibenthic sled, adredging device that captures organisms not just on and near the seafloor but also buried inthe sediments beneath. In a single one-hour trawl along the continental shelf, at a depth of justunder a mile, Woods Hole oceanographers Howard Sandler and Robert Hessler netted over25,000 creatures—worms, starfish, sea cucumbers, and the like—representing 365 species.
Even at a depth of three miles, they found some 3,700 creatures representing almost 200species of organism. But the dredge could only capture things that were too slow or stupid toget out of the way. In the late 1960s a marine biologist named John Isaacs got the idea tolower a camera with bait attached to it, and found still more, in particular dense swarms ofwrithing hagfish, a primitive eel-like creature, as well as darting shoals of grenadier fish.
Where a good food source is suddenly available—for instance, when a whale dies and sinks tothe bottom—as many as 390 species of marine creature have been found dining off it.
Interestingly, many of these creatures were found to have come from vents up to a thousandmiles distant. These included such types as mussels and clams, which are hardly known asgreat travelers. It is now thought that the larvae of certain organisms may drift through thewater until, by some unknown chemical means, they detect that they have arrived at a foodopportunity and fall onto it.
So why, if the seas are so vast, do we so easily overtax them? Well, to begin with, theworld’s seas are not uniformly bounteous. Altogether less than a tenth of the ocean isconsidered naturally productive. Most aquatic species like to be in shallow waters where thereis warmth and light and an abundance of organic matter to prime the food chain. Coral reefs,for instance, constitute well under 1 percent of the ocean’s space but are home to about 25percent of its fish.
Elsewhere, the oceans aren’t nearly so rich. Take Australia. With over 20,000 miles ofcoastline and almost nine million square miles of territorial waters, it has more sea lapping itsshores than any other country, yet, as Tim Flannery notes, it doesn’t even make it into the topfifty among fishing nations. Indeed, Australia is a large net importer of seafood. This isbecause much of Australia’s waters are, like much of Australia itself, essentially desert. (Anotable exception is the Great Barrier Reef off Queensland, which is sumptuously fecund.)Because the soil is poor, it produces little in the way of nutrient-rich runoff.
Even where life thrives, it is often extremely sensitive to disturbance. In the 1970s, fishermenfrom Australia and, to a lesser extent, New Zealand discovered shoals of a little-known fishliving at a depth of about half a mile on their continental shelves. They were known as orange1The indigestible parts of giant squid, in particular their beaks, accumulate in sperm whales stomachs into thesubstance known as ambergris, which is used as a fixative in perfumes. The next time you spray on Chanel No. 5(assuming you do), you may wish to reflect that you are dousing yourself in distillate of unseen sea monster.
roughy, they were delicious, and they existed in huge numbers. In no time at all, fishing fleetswere hauling in forty thousand metric tons of roughy a year. Then marine biologists madesome alarming discoveries. Roughy are extremely long lived and slow maturing. Some maybe 150 years old; any roughy you have eaten may well have been born when Victoria wasQueen. Roughy have adopted this exceedingly unhurried lifestyle because the waters they livein are so resource-poor. In such waters, some fish spawn just once in a lifetime. Clearly theseare populations that cannot stand a great deal of disturbance. Unfortunately, by the time thiswas realized the stocks had been severely depleted. Even with careful management it will bedecades before the populations recover, if they ever do.
Elsewhere, however, the misuse of the oceans has been more wanton than inadvertent.
Many fishermen “fin” sharks—that is, slice their fins off, then dump them back into the waterto die. In 1998, shark fins sold in the Far East for over $250 a pound. A bowl of shark finsoup retailed in Tokyo for $100. The World Wildlife Fund estimated in 1994 that the numberof sharks killed each year was between 40 million and 70 million.
As of 1995, some 37,000 industrial-sized fishing ships, plus about a million smaller boats,were between them taking twice as many fish from the sea as they had just twenty-five yearsearlier. Trawlers are sometimes now as big as cruise ships and haul behind them nets bigenough to hold a dozen jumbo jets. Some even use spotter planes to locate shoals of fish fromthe air.
It is estimated that about a quarter of every fishing net hauled up contains “by-catch”—fishthat can’t be landed because they are too small or of the wrong type or caught in the wrongseason. As one observer told the Economist: “We’re still in the Dark Ages. We just drop a netdown and see what comes up.” Perhaps as much as twenty-two million metric tons of suchunwanted fish are dumped back in the sea each year, mostly in the form of corpses. For everypound of shrimp harvested, about four pounds of fish and other marine creatures aredestroyed.
Large areas of the North Sea floor are dragged clean by beam trawlers as many as seventimes a year, a degree of disturbance that no ecosystem can withstand. At least two-thirds ofspecies in the North Sea, by many estimates, are being overfished. Across the Atlantic thingsare no better. Halibut once abounded in such numbers off New England that individual boatscould land twenty thousand pounds of it in a day. Now halibut is all but extinct off thenortheast coast of North America.
Nothing, however, compares with the fate of cod. In the late fifteenth century, the explorerJohn Cabot found cod in incredible numbers on the eastern banks of North America—shallowareas of water popular with bottom-feeding fish like cod. Some of these banks were vast.
Georges Banks off Massachusetts is bigger than the state it abuts. The Grand Banks offNewfoundland is bigger still and for centuries was always dense with cod. They were thoughtto be inexhaustible. Of course they were anything but.
By 1960, the number of spawning cod in the north Atlantic had fallen to an estimated 1.6million metric tons. By 1990 this had sunk to 22,000 metric tons. In commercial terms, thecod were extinct. “Fishermen,” wrote Mark Kurlansky in his fascinating history, Cod, “hadcaught them all.” The cod may have lost the western Atlantic forever. In 1992, cod fishingwas stopped altogether on the Grand Banks, but as of last autumn, according to a report inNature, stocks had not staged a comeback. Kurlansky notes that the fish of fish fillets and fish sticks was originally cod, but then was replaced by haddock, then by redfish, and lately byPacific pollock. These days, he notes drily, “fish” is “whatever is left.”
Much the same can be said of many other seafoods. In the New England fisheries offRhode Island, it was once routine to haul in lobsters weighing twenty pounds. Sometimes theyreached thirty pounds. Left unmolested, lobsters can live for decades—as much as seventyyears, it is thought—and they never stop growing. Nowadays few lobsters weigh more thantwo pounds on capture. “Biologists,” according to the New York Times, “estimate that 90percent of lobsters are caught within a year after they reach the legal minimum size at aboutage six.” Despite declining catches, New England fishermen continue to receive state andfederal tax incentives that encourage them—in some cases all but compel them—to acquirebigger boats and to harvest the seas more intensively. Today fishermen of Massachusetts arereduced to fishing the hideous hagfish, for which there is a slight market in the Far East, buteven their numbers are now falling.
We are remarkably ignorant of the dynamics that rule life in the sea. While marine life ispoorer than it ought to be in areas that have been overfished, in some naturally impoverishedwaters there is far more life than there ought to be. The southern oceans around Antarcticaproduce only about 3 percent of the world’s phytoplankton—far too little, it would seem, tosupport a complex ecosystem, and yet it does. Crab-eater seals are not a species of animal thatmost of us have heard of, but they may actually be the second most numerous large species ofanimal on Earth, after humans. As many as fifteen million of them may live on the pack icearound Antarctica. There are also perhaps two million Weddel seals, at least half a millionemperor penguins, and maybe as many as four million Adélie penguins. The food chain isthus hopelessly top heavy, but somehow it works. Remarkably no one knows how.
All this is a very roundabout way of making the point that we know very little about Earth’sbiggest system. But then, as we shall see in the pages remaining to u