The World Without Us

If not, and if no humans return to till the soil or husband the animals, forests will take over. Rangelands that receive good rainfall will welcome new grazers—or old ones, as some new incarnation of Proboscidae and sloths replenish the Earth. Other places, however, less blessed, will have parched into new Saharas. The American Southwest, for instance: waist-high in grasses until 1880, when their cattle population of a half-million suddenly sextupled, New Mexico and Arizona now face unprecedented drought, with much of their water-retaining capacity lost. They may have to wait.

Still, the Sahara itself was once covered with rivers and ponds. With patience—though not, unfortunately, human patience—it will be again.

PART III

CHAPTER 12 The Fate of Ancient and Modern Wonders of the World

BETWEEN 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.