Behind that gray urban facade begins one of the world’s largest, poorest slums. Nairobi is only as old as the railroad that needed a depot between Mombasa and Victoria. One of the youngest cities on Earth, it will likely be among the first to go, because even new construction here quickly begins to crumble.

City of contrasts

On its opposite end, Nairobi National Park is unfenced. The Cessna passes its unmarked boundary, crossing into a gray plain dotted with morning-glory trees.

Nairobi is one of the youngest cities on Earth and it will likely be among the first to go, because even new construction here quickly begins to crumble.

Through here, the park’s migrating wildebeest, zebra and rhinos follow seasonal rains along a corridor lately pinched by maize fields, flower farms, eucalyptus plantations and sprawling new fenced estates with private wells and conspicuous large houses. Together, these may turn Kenya’s oldest national park into yet another wildlife island.

The corridor isn’t protected. With real estate outside of roiling Nairobi becoming increasingly attractive, the best option, in the opinion of the Cessna’s pilot, David Western, is for the government to pay owners to let animals cross their property. He’s helped with negotiations, but he’s not hopeful. Everyone fears elephants squashing their gardens, or worse.

Wildlife specialist

Counting elephants is David Western’s project today — something he has done continually for nearly three decades. Raised in Tanzania, son of a British big-game hunter, as a boy he often hiked alongside his gun-toting father for days without seeing another human.

The first animal he shot was his last. The look in the dying warthog’s eyes cooled any further passion to hunt. After an elephant fatally gored his father, his mother took her children to the comparative safety of London. David stayed through university studies in zoology, then returned to Africa.

Changing lifestyles

An hour southeast of Nairobi, Kilimanjaro appears, its shrinking snowcap dripping butterscotch under the rising sun. Just before it, verdant swamps burst from a brown alkaline basin, fed by springs from the volcano’s rainy slopes.

With real estate outside of roiling Nairobi becoming increasingly attractive, the best option is for the government to pay owners to let animals cross their property.

This is Amboseli, one of Africa’s smallest, richest parks — an obligatory pilgrimage for tourists hoping to photograph elephants silhouetted against Kilimanjaro.

That used to be a dry-season event, when wildlife would pack into Amboseli’s marshland oasis to survive on cattails and sedges. Now they’re always here. “Elephants aren’t supposed to be sedentary,” Western mutters as he passes over dozens of females and calves wading not far from a pod of mucking hippos.

From high above, the plain surrounding the park seems infected by giant spores. These are bomas: Rings of mud-and-dung huts belonging to Maasai pastoralists, some occupied, some abandoned and melting back into the earth.

The Maasai

A defensive ring of stacked, thorny acacia branches encircles each. The bright green patch in every compound’s center is where the nomadic Maasai keep cattle safe from predators at night before moving their herds and families to the next pasture.

As Maasai move out, elephants move in. Since people first brought cattle down from northern Africa after the Sahara dried, a choreography has evolved featuring elephants and livestock. After cattle chew savanna grasses down, woody shrubs invade.

Helping each other

Soon they’re tall enough for elephants to munch, using their

Amboseli is one of Africa’s smallest, richest parks — and an obligatory pilgrimage for tourists hoping to photograph elephants silhouetted against Kilimanjaro.

tusks to strip and eat bark, knocking trees over to reach their tender canopies, clearing the way for grass to return.

As a graduate student, David Western sat atop an Amboseli hill, counting cows led to graze by Maasai herders as elephants plodded in the opposite direction to browse.

The census he began here of cattle, elephants and people has never stopped during his subsequent careers as Amboseli park director, head of the Kenya Wildlife Service — and founder of the nonprofit African Conservation Centre, which works to preserve wild habitats by accommodating, not banning, humans who have traditionally shared them.

Maasai lifestyle

Dropping to 300 feet, he begins flying wide, clockwise circles, banked at a 30° angle. He tallies a ring of dung-plastered huts — one hut per wife. Some wealthy Maasai have as many as 10 wives. He calculates the approximate number of inhabitants, and notes 77 cattle on his vegetation map.

What looked from above like blood drops on a green plain turns out to be the Maasai herders themselves. Tall, lithe, dark men in traditional red plaid shoulder cloaks — traditional, at least, since the 19th century, when Scottish missionaries distributed tartan blankets that Maasai herdsmen found both warm and light enough to carry as they followed their herds for weeks.

Migrating people

“The pastoralists,” Western shouts

Since people first brought cattle down from northern Africa, a choreography has evolved featuring elephants and livestock. After cattle chew grasses down, woody shrubs invade. Soon they’re tall enough for elephants to munch, clearing the way for grass to return.

over the engine noise, “have become a surrogate migratory species. They behave much like wildebeest.” Like the wildebeest, Maasai herd their cows into short-grass savannas during wet seasons and bring them back to water holes when the rains stop.

Over a year, Amboseli’s Maasai live in an average of eight settlements. Such human movement, Western is convinced, has literally landscaped Kenya and Tanzania to the benefit of wildlife.

“They graze their cattle and leave behind woodland for elephants. In time, elephants create grassland agaiti. You get a patchy mosaic of grass, woods and shrublands. That’s the whole reason for the savanna’s diversity. If you only had woodlands or grasslands, you would only support wood land species or grassland species.”

Problem of poaching

During the 1970s and 1980s, elephants learned the hard way to stay where they were safe.

Unwittingly, they lumbered into a global collision between deepening African poverty, which in Kenya was yoked to the planet’s highest birthrate — and the boom that spawned the so-called Asian economic tigers — which unleashed a craving in the Far East for luxuries. These included ivory and the desire for it outstripped even the lust that once financed centuries of slavery.

High-priced ivory

As the price — $20 per kilo — rose by a factor of 10, ivory poachers turned places like Tsavo into a trash heap of

The fever tree acacias that once lined Amboseli’s swamps are now gone. It is a man-made replica of extreme drought, such as Africa knew during ice ages, when habitats shriveled and creatures crammed into oases.

tuskless carcasses. By the 1980s, more than half of Africa’s 1.3 million elephants were dead. Only 19,000 were left in Kenya, packed into sanctuaries such as Amboseli.

International ivory bans and shoot-to-kill orders for poachers calmed but never eradicated the carnage, especially the slaughter of elephants outside parks on the pretext of defending crops or people.

The fever tree acacias that once lined Amboseli’s swamps are now gone, downed by overcrowded pachyderms. As parks become treeless plains, desert creatures like gazelles and oryx replace browsers like giraffes, kudus and bushbuck. It is a man-made replica of extreme drought, such as Africa knew during ice ages, when habitats shriveled and creatures crammed into oases.

Destruction through urbanization

Africa’s megafauna made it through those bottlenecks, but David Western fears what may happen to them in this one — stranded on island refuges in a sea of settlements, subdivisions, exhausted pastures and factory farms.

For thousands of years, migratory humans were their escorts across Africa: Nomads and their herds taking what they needed and moving on, leaving nature even richer in their wake.

But now such human migration is coming to a close. Homo sedentarian has flipped that scenario. Food now migrates to us, along with luxury goods and other consumables that never existed through most of human history.