Africa After Us

In an Africa without humans, as elephants push above the equator through Samburo and then beyond the Sahel, they may find a Sahara Desert in northward retreat, as desertification’s advance troops — goats — become lunch for lions.

Or, they may collide with it, as temperatures rising on a wave of a human legacy, elevated atmospheric carbon, quicken its march. That the Sahara has lately advanced so rapidly and alarmingly — in places, two to three miles per year — owes to unfortunate timing.

Only 6,000 years ago, what is now the world’s largest nonpolar desert was green savanna. Crocodiles and hippos wallowed in plentiful Sahara streams. Then Earth’s orbit underwent one of its periodic readjustments. Our tilted axis straightened not even half a degree, but enough to nudge rain clouds around.

That alone was not sufficient to turn grasslands to sand dunes. But the coincidence of human progress tipped what was becoming an arid shrub land over a climatic edge. During two previous millennia, in North Africa, Homo sapiens had gone from hunting with spears to growing Middle Eastern grains and raising livestock.

They mounted their belongings, and themselves, on newly tamed descendants of an American ungulate that luckily emigrated before its cousins back home perished in a mega faunal holocaust: The camel.

Camels eat grass — grass needs water. So did their masters’ crops, whose bounty begat a population boom of humans. More humans needed more herds, pasture, fields and more water — all at just the wrong time. No one could have known that the rains had shifted.

So people and their flocks ranged farther and grazed harder, assuming that the weather would return to what it had been, and that everything would grow back the way it was.

It didn’t. The more they consumed, the less moisture transpired sky ward and the less it rained. The result was the hot Sahara we see today. Only it used to be smaller.

Over this past century, the numbers of Africa’s humans and their animals have been rising, and now temperatures are, too. This leaves the precarious sub-Saharan tier of Sahel countries at the brink of sliding into the sand.

Farther south, equatorial Africans have herded animals for several thousand years and hunted them even longer, yet between wildlife and humans there was actually mutual benefit. As pastoralists such as Kenya’s Maasai shepherded cattle among pastures and water holes, their spears ready to discourage lions, wildebeest tagged along to take advantage of the predator protection.

They, in turn, were followed by their zebra companions. The nomads economized by eating meat sparingly, learning to live on their flocks’ milk and blood, which they drew by carefully tapping and staunching their cattle’s jugular veins. Only when drought reduced fodder for their herds did they fall back on hunting or trade with bushmen tribes that still lived off game.

This balance among humans, flora and fauna first began to shift when humans became prey themselves — or rather, commodities. Like our kin the chimpanzees, we’d always murdered one another over territory and mates. But with the rise of slavery, we were reduced to something new: An export crop.

The mark that slavery left on Africa can be seen today in southeastern Kenya, in brushy country known as Tsavo, an eerie landscape of lava-flows, flat-topped tortilis acacias, myrrh and baobab trees.

Because Tsavo’s tsetse flies discouraged cattle herding, it remained a hunting ground for Waata bushmen. Their game included elephant, giraffe, cape buffalo, assorted gazelles, klipspringer and another striped antelope: The kudu, its horns corkscrewing for an amazing six feet.

The destination for black slaves in East Africa was not America, but Arabia. Until the mid-19th century, Mombasa, on Kenya’s coast, was the shipping port for human flesh, the end of a long line for Arab slavers who captured their merchandise at gunpoint in central African villages.

Editor’s Note: Copyright 2007 St. Martin’s Press. Reprinted with the permission of the publisher.