The World Without Us - Alan Weisman (2007)

Part III

Chapter 12. The Fate of Ancient and Modern Wonders of the World


ETWEEN GLOBAL WARMING and ocean-conveyor cooling, if whichever dominates is partly muted by the other, as some models propose, Europe’s meticulous mechanized farmlands would, without humans, fill with brome and fescue grass, lupine, plumed thistle, flowering rapeseed, and wild mustard. Within a few decades oak shoots would sprout from the acidic former fields of wheat, rye, and barley. Boars, hedgehogs, lynx, bison, and beaver would spread, with wolves moving up from Romania and, if Europe is cooler, reindeer coming down from Norway.

The British Isles would be somewhat biologically marooned, as rising seas batter the already-receding chalk cliffs of Dover and widen the 21-mile gap that separates England from France. Dwarf elephants and hippopotamuses once may have swum almost double that distance to reach Cyprus, so presumably something might try. Caribou, buoyed by their insulating hollow hair, cross northern Canadian lakes, so their reindeer siblings might just make it to England.

Should some impetuous animal attempt the journey via Chunnel— the English Channel Tunnel, Le Tunnel sous la Manche—after human traffic ceases, it might actually make it. Even without maintenance, the Chunnel wouldn’t quickly flood like many of the world’s subways, because it was dug within a single geologic layer, a bed of chalk marl with minimal filtration.

Whether an animal would actually try is another matter. All three Chunnel tubes—one each for westbound and eastbound trains, and a parallel central corridor to service them—are swaddled in concrete. For 35 miles there would be no food or water—just pitch darkness. Still, it’s not impossible that some continental species might recolonize Britain that way: The capacity of organisms to ensconce themselves in the world’s most inhospitable places—from lichens on Antarctic glaciers to sea worms in 176°F sea vents—may symbolize the meaning of life itself. Surely, as small, curious creatures like voles or the inevitable Norway rats slither down the Chunnel, some brash young wolf will follow their scent.

The Chunnel is a true wonder of our times, and, at a cost of $21 billion, also the most expensive construction project ever conceived until China began damming several rivers at once. Protected by its buried bed of marl, it has one of the best chances of any human artifact to last millions of years, until continental drift finally pulls it apart or scrunches it like an accordion.

While still intact, however, it may not remain functional. Its two terminals are just a few miles from their respective coasts. There’s little chance that the Folkestone, England, entrance, nearly 200 feet above current sea level, could be breached: the chalk cliffs that separate it from the English Channel would have to erode significantly. Far more likely is that ascending waters could enter the Coquelles, France, terminal, only about 16 feet above sea level on the Calais plain. If so, the Chunnel would not completely flood: the marl stratum it follows makes a mid-channel dip and then rises, so water would seek the lowest levels, leaving part of the chambers clear.

Clear, but useless, even to daring migrating creatures. But when $21 billion was spent to create one of engineering’s greatest wonders, no one imagined that the oceans might rise up against us.

Nor did the proud builders of the ancient world, which had seven wonders, dream that in a span far shorter than eternity only one of them— Egypt’s Khufu pyramid—would remain. Like old-growth forest whose lofty treetops eventually collapse, Khufu has shrunk some 30 feet over the past 4,500 years. At first, that was no gradual loss—its marble shell was cannibalized during the Middle Ages by conquering Arabs to build Cairo. The exposed limestone is now dissolving like any other hill, and in a million more years should not look very pyramidal at all.

The other six were of even more mortal stuff: a huge wooden idol of Zeus plated in ivory and gold, which fell apart during an attempt to move it; a hanging garden, of which no trace remains among the ruins of its Babylonian palace 30 miles south of Baghdad; a colossal bronze statue on Rhodes that collapsed under its own weight in an earthquake and was later sold for scrap; and three marble structures—a Greek temple that crumbled in a fire, a Persian mausoleum razed by Crusaders, and a lighthouse marking Alexandria’s harbor, which was felled by earthquake as well.

What made them qualify as wonders was sometimes stirring beauty, as in the case of the Temple of Artemis in Greece, but more often it was simply massive scale. Human creation writ very large often overwhelms us into submission. Less ancient, but most imposing of all, is a construction project that spanned 2,000 years, three ruling dynasties, and 4,000 miles, resulting in a rampart so monumental that it achieved the status not just of landmark, but landform. The Great Wall of China is so staggering that it was widely, although erroneously, believed visible from outer space, serving notice even to would-be attackers from other worlds that this property was defended.

Yet, like any other ripple in the Earth’s crust, the Great Wall is not immortal, and far less so than most geologic versions. A pastiche of rammed earth, stones, fired brick, timbers, and even glutinous rice used as mortar paste, without human maintenance it is defenseless against tree roots and water—and the highly acidic rain produced by an industrializing Chinese society isn’t helping. Yet without that society, it will steadily melt away until just the stones remain.

Walling the Earth from the Yellow Sea all the way across Inner Mongolia is impressive, but for grand public works, few have matched a modern wonder whose construction began in 1903, the same year that New York inaugurated its subway. It was no less than the human race defying plate tectonics by tearing apart two continents that floated together 3 million years earlier. Nothing like the Panama Canal had ever been attempted before, and little has come close to it since.

Although the Suez Canal had already severed Africa from Asia three decades earlier, that was a comparatively simple, sea-level surgical stroke across an empty, disease-free sand desert with no hills. The French company that dug it went next to the 56-mile-wide isthmus between the Americas, smugly intending to do the same. Disastrously, they underestimated dense jungle steeped in malaria and yellow fever, rivers fed by prodigious rainfall, and a continental divide whose lowest pass was still 270 feet above the sea. Before they were one-third of the way through, they suffered not only a bankruptcy that rocked France, but also the deaths of 22,000 workers.

Nine years later, in 1898, a highly ambitious Assistant Secretary of the Navy named Theodore Roosevelt found a pretext, based on an explosion (probably due to a faulty boiler) that sank a U.S. ship in Havana Harbor, to oust Spain from the Caribbean. The Spanish-American War was intended to liberate both Cuba and Puerto Rico, but, to the great surprise of Puerto Ricans, the United States annexed their island. To Roosevelt, it was perfectly positioned as a coaling station for the still-nonexistent canal that would eliminate the need for ships sailing between the Atlantic and the Pacific to travel down the length of South America and up again.

Roosevelt chose Panama over Nicaragua, whose eponymous navigable lake, which would have saved considerable digging, lay among active volcanoes. At the time, the isthmus was part of Colombia, although Panamanians had tried three times to bolt from distant Bogota’s fitful rule. When Colombia objected to the U.S. offer of just $10 million for sovereignty over a 6-mile-wide zone bordering the proposed canal, President Roosevelt sent a gunboat to help Panamanian rebels finally succeed. A day later, he betrayed them by recognizing as Panama’s first ambassador to the United States a French engineer from France’s defunct canal-digging company, who, at considerable personal profit, immediately affirmed a treaty agreeing to U.S. terms.

That sealed the United States’ reputation in Latin America as piratical gringo imperialists, and produced—11 years and 5,000 more deaths later—the most stunning engineering feat yet in human history. More than a century has passed and it is still among the greatest of all time. Besides reconfiguring continental landmasses and communication between two oceans, the Panama Canal also significantly shifted the economic center of the world to the United States.

Something that substantial and literally earth-moving seems destined to last for the ages. But in a world without us, how long would it take nature to rejoin what man split asunder in Panama?

“THE PANAMA CANAL,” says Abdiel pérez, “is like a wound that humans inflicted on the Earth—one that nature is trying to heal.”

As superintendent of the locks on the Canal’s Atlantic side, Pérez— along with 5 percent of all planetary commerce—depends on a handful of hydrologists and engineers charged with keeping that wound open. A square-jawed, soft-voiced electrical and mechanical engineer, Pérez began here in the 1980s as an apprentice machinist while studying at the University of Panama. Daily, he feels humbled to be entrusted with one of the most revolutionary pieces of machinery on Earth.

“Portland cement was a novelty. This is where it was tried out. Reinforced concrete wasn’t invented yet. All the walls of the locks are oversized like a pyramid. Their only reinforcement is gravity.”

He stands alongside what is essentially a huge concrete box, into which an orange Chinese freighter bound for the East Coast of the United States, stacked seven stories high with containers, has just been guided. The lock is 110 feet wide. The ship, as long as three football fields, has exactly two feet of clearance on each side as two electric railway engines, called mules, tug it through the glove-tight locks.

“Electricity was also new. New York had barely installed the first generating plant. But the Canal builders decided to use electricity, not steam engines.”

Once the ship is inside, water is piped into the lock to raise it 28 feet, which takes ten minutes. On the lock’s opposite end awaits Lake Gatun, for a half-century the biggest artificial lake in the world. Creating it drowned an entire mahogany forest, but prevented a repeat of the French debacle, which resulted from the fatal decision to try digging another sea-level canal like Suez. Besides entailing removal of a large chunk of the continental divide, there was also the matter of the Río Chagres, a rain-gorged river that, as it plunged from jungle highlands to the sea, smacked into the middle of the canal’s route. During Panama’s eight-month rainy season, the Chagres carried enough silt to plug a narrow man-made channel in mere days, if not hours.

The Americans’ solution was to build an aquatic staircase fashioned by three locks on either end, rising in watery steps to a lake formed by the dammed Chagres in the middle—a liquid bridge over which boats could float across the hills that the French failed to cut through. The locks use 52,000 gallons of water to lift every ship that passes through—freshwater fed by gravity from the trapped river, which drains to the sea as each vessel exits. Although gravity is always available, the electricity that opens and closes the doors of each lock depends on human operators who maintain hydroelectric generators that also tap the Chagres.

There are also auxiliary steam power and a diesel plant, but, says Pérez, “without people, the electricity wouldn’t last a day. Someone in control must decide where the power’s coming from, whether to open or close turbines, et cetera. With no human in the system, it doesn’t work.”

What particularly wouldn’t work are the 7-foot-thick hollow, floating steel doors, 80 feet high and 65 feet wide. Each lock has a double set as backup, pivoting on plastic bearings that, during the 1980s, replaced the original brass hinges that corroded every few decades. What if power were cut, and the doors opened and stayed that way?

“Then it’s all over. The highest lock is 137 feet above sea level. Even if they were left closed, once their seals went, so would the water.” The seals are steel plates overlapping each door’s leading edge, which need replacing every 15 to 20 years. Pérez glances up as the shadow of a frigate bird speeds past, then resumes watching the double doors close behind the departing Chinese freighter.

“The whole lake could empty through the locks.”

Gatun Lake sprawls over what was once the course of the Río Chagres as it emptied into the Caribbean. Reaching it from the Pacific side required cutting through the 12 miles of terrestrial spine that bisects Panama lengthwise at La Culebra, the lowest saddle in the continental divide. Slicing through that much soil, iron oxide, clay, and basalt would have been daunting anywhere, but even after the French disaster, no one really understood how truly unstable the waterlogged Panamanian earth was.

The Culebra Cut initially was to be 300 feet wide. As one gigantic mudslide after another undid months of digging, sometimes burying boxcars and steam shovels as it refilled the trench, engineers had to keep widening the slope. In the end, the mountain range that runs from Alaska to Tierra del Fuego was separated in Panama by a man-made valley, its gap about six times as broad as its floor. To dig it required the labor of 6,000 men every day for seven years. The 100 million-plus cubic yards of dirt they moved, if compacted together, would form an asteroid one-third of a mile across. More than a century since its completion, work on Culebra Cut has never entirely ceased. With silt constantly accumulating, and frequent small landslides, each day dredging rigs with suction pumps and shovels work up one side of the canal as ships come down the other.

In the green mountains 20 miles northeast of the Culebra Cut, two Panama Canal hydrologists, Modesto Echevers and Johnny Cuevas, stand on a concrete abutment above Lake Alajuela, created by yet another dam, one that had to be built upriver on the Chagres in 1935. The Chagres watershed is one of the rainiest places on Earth, and during the Canal’s first two decades, several floods slammed into it. Boat traffic halted for hours while floodgates were opened, lest the pounding of the river cave in its banks. The flood of 1923, which carried entire uprooted mahogany trunks, created a surge on Lake Gatun powerful enough to tip over ships.

Madden Dam, the wall of concrete that holds back the river to form Lake Alajuela, also sends electricity and drinking water to Panama City. But to keep its reservoir from leaking out the sides, engineers had to fill 14 dips in the terrain with earth to create its rim. Down below, massive Lake Gatun is also surrounded by earthen saddle dams. Some are so overgrown with rain forest that an untrained eye can’t see that they are artificial— which is why Echevers and Cuevas must come up here every day: to try to stay ahead of nature.

“Everything grows so fast,” explains Echevers, a burly man in a blue rain jacket. “When I started doing this, I came here looking for Dam Number 10, and I couldn’t find it. Nature had eaten it.”

Cuevas nods, eyes closed, recalling many battles with roots that can tear an earthen dam apart. The other enemy is the trapped water itself. During a rainstorm, these men are often here all night, fighting to maintain a balance between holding the Chagres at bay and releasing enough water through the concrete wall’s four floodgates to assure that nothing bursts.

Map of Panama Canal.


But if one day there were no people around to do that?

Echevers shudders at the thought, because he’s seen how the Chagres reacts to rain: “Like a zoo animal that has never accepted its cage. The water loses control. If it was allowed to rise, it would top the dam.”

He stops to watch a pickup truck roll across the raised roadway that runs along the top of the dam. “If no one were here to open the floodgates, the lake would fill up with branches, tree trunks, and garbage, and at some point all that stuff would hit the dam and take the road with it.”

Cuevas, his quiet colleague, has been mentally calculating. “The head of the river would be huge when it goes over the top. Like a waterfall, it would erode away the river bottom in front of the dam. One really big flood could collapse the dam.”

Even if that never happened, they agree, eventually the spillway gates would rust away. “At that point,” says Echevers, “a 20-foot head of water would break free. Drastically.”

They look down at the lake where, 20 feet below, an eight-foot alligator floats motionless in the dam’s shadow, then streaks through the teal blue water as an unlucky terrapin surfaces. Madden Dam’s concrete wedge looks too solid to go anywhere. Yet one rainy day, it will likely flop over.

“Even if it survives,” says Echevers, “with no one here the Chagres will fill the lake with sediment. At that point, the dam won’t matter.”

In a chain-link compound where Panama City now spills into the former Canal Zone, Port Captain Bill Huff sits in jeans and a golf shirt before a wall of maps and monitors, guiding evening traffic through the Canal. A U.S. citizen born and raised here—his grandfather, a Canal Zone shipping agent, arrived in the 1920s—he moved to Florida after sovereignty over the Canal passed from the United States to Panama as the clock ticked off the first second of the new millennium. But his 30 years of experience were still in demand, and, now in the employ of Panama, he returns every few months to take a shift.

He switches a screen to a view of Lake Gatun’s dam, a low mound of earth 100 feet wide. Its submerged base is 20 times thicker. To the casual observer, there’s not much to see. But someone has to be looking all the time.

“There are springs underneath the dam. A couple of small ones have pierced through. If water runs clear, no problem. Clear water means it’s coming up through the bedrock.” Huff pushes back in his chair and rubs the dark beard circling his chin. “But if water starts bringing dirt with it, then the dam is doomed. In just a matter of hours.”

It’s hard to imagine. Gatun Dam has a 1,200-foot-thick, theoretically impermeable central core of rock and gravel cemented with liquid clays that are known as fines, sluiced up from the dredged channel below and tamped between two buried rock walls.

“The fines hold the gravel and everything together. They’re what starts coming out first. Then the gravel follows, and the dam loses its adhesion.”

He opens a long drawer in an old pine desk and pulls out a map tube. Unrolling a yellowed, laminated chart of the isthmus, he points to Gatun Dam, just six miles from the Caribbean. On the ground, it’s an impressive mile-and-a-half long, but on the map it’s clearly just a narrow gap compared to the tremendous expanse of water dammed behind it.

The hydrologists Cuevas and Echevers are right, he says. “If not during the first rainy season, within just a few years it would be the end of Madden Dam. That lake would all come pouring down into Gatun Lake.”

Gatun Lake would then start spilling over the locks on both sides, toward the Atlantic and the Pacific. For a while a casual observer might not notice much, “except maybe unkept grass.” The Canal’s prim landscaping, still maintained to American military standards, would start to turn lush. But before any palms or figs moved in, a flood would take over.

“Big surges of water would sluice around the locks and scour bypasses into the dirt. Once one of the lock walls started to tumble, that would be the end. All of Gatun Lake could spill.” He pauses. “That is, if it hadn’t already emptied into the Caribbean. After 20 years with no maintenance, I don’t see earthen dams left. Especially Gatun.”

At that point, the liberated Chagres River, which drove many French and American engineers crazy and thousands of laborers to their death, would seek its old channel to the sea. With the dams gone, the lakes empty, and the river again headed east, the Pacific side of the Panama Canal would dry up, and the Americas would be reunited.

The last time that happened, 3 million years ago, one of the greatest biological interchanges in Earth’s history commenced as North and South American land species began to travel the Central American isthmus, which now joined them.

Until then, the two landmasses had been separated since the supercontinent of Pangea began to break up about 200 million years earlier. During that time, the two separate Americas had embarked on enormously different evolutionary experiments. Like Australia, South America developed a menagerie of marsupial mammals, ranging from sloths to even a lion that carried its young in a pouch. In North America, a more efficient, ultimately triumphant placental path emerged.

This most recent man-made separation has existed for little more than a century—not enough time for any meaningful species evolution, and a canal barely wide enough for two ships to pass each other has hardly been much of a barrier. Still, speculates Bill Huff, until roots work their way into the cracks in the huge, empty concrete boxes that once held ocean-going vessels and finally shatter them, for a few centuries they will be rain-catch holes prowled by panthers and jaguars, as regenerating tapir, white-tailed deer, and anteaters come to drink.

Even longer than those boxes, for a while a big man-made, V-shaped gouge would remain, marking the place where humans undertook, in the words of Theodore Roosevelt after he went to Panama in 1906 to see for himself, “the greatest engineering feat of the ages. The effect of their work,” he added, “will be felt while our civilization lasts.”

If we disappeared, the words of this larger-than-life American president, who founded a national park system and institutionalized North American imperialism, would prove prophetic. Yet long after the walls of the Culebra Cut cave in, one last larger-than-life monument to Roosevelt’s grand vision for the Americas will remain.

IN 1923, SCULPTOR Gutzon Borglum was commissioned to immortalize the greatest American presidents in portraits every bit as imposing as that long-vanished wonder, the Colossus of Rhodes. His canvas was an entire South Dakota mountainside. Along with George Washington, father of the country; Thomas Jefferson, drafter of its Declaration of Independence and Bill of Rights; and Abraham Lincoln, the emancipator and reuniter, Borglum insisted on portraying Theodore Roosevelt, who joined the seas.

The site he selected for what qualifies as the United States’ national magnum opus, Mount Rushmore, is a 5,725-foot uplift composed of fine-grained Precambrian granite. When Borglum died in 1941 of a brain hemorrhage, he’d barely begun work on the presidential torsos. But the faces were all indelibly carved in stone; he lived to see the visage of his personal hero, Teddy Roosevelt, officially dedicated in 1939.

He’d even rendered Roosevelt’s trademark pince-nez in rock—a rock formed 1.5 billion years ago, among the most resistant on the continent. According to geologists, Mount Rushmore’s granite erodes only one inch every 10,000 years. At that rate, barring asteroid collision or a particularly violent earthquake in this seismically stable center of the continent, at least vestiges of Roosevelt’s 60-foot likeness, memorializing his Canal, will be around for the next 7.2 million years.

In less time than that, Pan prior became us. Should some equally ingenious, confounding, lyrical, and conflicted species appear on Earth again in our aftermath, they may still find T.R.’s fierce, shrewd gaze fixed intently upon them.