The World Without Us

“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.