This story appears in the November 2017 issue of National Geographic magazine.



Seen from space, high above Africa, the Okavango Delta resembles a gigantic starburst blossom pressed onto the landscape of northern Botswana, its stem angling southeastward from the Namibian border, its petals of silvery water splayed out for a hundred miles across the Kalahari Basin. It is one of the planet’s great wetlands, a vast splash of life-nurturing channels and lagoons and seasonal ponds amid a severely dry region of the continent.

This delta doesn’t open to the sea. Contained entirely within the basin, it comes to a halt along a southeastern perimeter and disappears into the deep Kalahari sands. It can be thought of as the world’s largest oasis, a wet refuge supporting elephants, hippos, crocodiles, and wild dogs; lechwe and sitatungas and other wetland antelopes; warthogs and buffalo, lions and zebras, and birdlife of wondrous diversity and abundance—not to mention a tourism industry worth hundreds of millions of dollars annually. But from high in space, you won’t see the hippos on their day beds. You won’t see the wild dogs hunkered in shade beneath thorn scrub or the glad expressions on the faces of visitors and local entrepreneurs. Another thing you won’t see is the source of all that water.

View Images National Geographic’s Okavango Wilderness Project is an effort to survey, and ultimately help protect, the delta’s headwaters. It began in 2015 with an expedition on Angola’s Cuito River, so narrow here, near its source, that the team’s loaded boats had to be dragged for eight days.

The water comes almost entirely from Angola, Botswana’s complicated neighbor, two countries away. It begins in the moist highlands of Angola’s rainy center and flows toward the country’s southeast, quickly in one major drainage, the Cubango, and more slowly in another, the Cuito, where it pools into source lakes; percolates slowly through grassy floodplains, peat deposits, and underlying sand; and seeps into tributaries. The Cuito and Cubango Rivers converge at the southern Angolan border, forming a bigger river, the Okavango, which flows across the Caprivi Strip, a narrow band of Namibia, and into Botswana. On average, 2.5 trillion gallons of water a year flows in.

Take away that liquid gift, rendered by Angola to Botswana each year, and the Okavango Delta would cease to exist. It would become something else, and that something would not include hippos, sitatungas, or African fish eagles. If southern Africa were a vast golf course, Okavango with the faucets closed would be one of its sand traps.

Changes now occurring or foreseeable in southeastern Angola—in land use, water diversion, population density, and commerce—make this dark prospect a real possibility. That’s why the Cuito and Cubango Rivers, two remote waterways, have quietly attained high interest in certain circles. That’s why an international group of scientists, government officials, resource planners, and hardy young explorers, brought together by a fervent South African conservation biologist named Steve Boyes, with support from the National Geographic Society, has embarked on a grand effort of exploration, data gathering, and conservation advocacy called the Okavango Wilderness Project. These collaborators recognize that the well-being and future of the Okavango Delta is at stake—and that the well-being and future of southeastern Angola, a hard landscape, a poor cousin to glorious Okavango, is at stake too.

View Images Hippos, abundant in the delta and in the rivers that feed it, graze by night on land and rest by day in water. Males fight over territory, females protect their young—and their long, self-sharpening canine teeth can be lethal to intruders.

“We’re on borrowed time,” Boyes told me, as we sat at a campsite along the Cubango River earlier this year after a long day of paddling our mokoros (Okavango-style canoes) downstream. Having grown up in Johannesburg, with a passion for nature, Boyes worked for years at various jobs—a bartender at wineries, a naturalist and guide, a camp manager in the Okavango Delta. Along the way he finished a doctorate. By 2007 he had become acutely aware of the water-source issue and tried to raise the alert among people of Botswana but mostly met fatalism.

“They were just not interested,” he said, recalling a typical reaction: Yeah, Angola is such a terrible, bad place, and it’s such a shame the river may die. That goaded him to action. He began looking north, toward the headwaters. “We are going to do this,” he vowed. “We’re going to try and understand what this system is about.” In fact he hoped not just to understand it but to help preserve it.

Angola in 2017 may seem an unlikely site for visionary conservation efforts, yet it could also offer unusual opportunities. It is ravaged by war but now at peace. From the early 1960s until the start of the new millennium, Angola was high on the list of nations you would not want to visit—unless you were a mercenary soldier or a diamond buyer. Once a Portuguese colony, it got its independence in 1975 after a bloody war of liberation, then was wracked by civil war for 27 years, a proxy battleground for the superpowers, pustulated with land mines, a scene of great suffering and strife.

View Images Project leader Steve Boyes (right) takes a break with National Geographic filmmaker Neil Gelinas. Among all the challenges Boyes has faced in more than 10 years of field science aimed at safeguarding the Okavango—diplomacy, capsized boats, land mines— an attack of sweat bees is just one more thing.

But things have changed drastically since 2002, when the rebel party, UNITA, suffered a crushing defeat, after which oil in great quantities began flowing for export and business boomed. “The most important thing we have to tell the world is that Angola is now a stable country,” the minister of the environment, Maria de Fátima Monteiro Jardim, told me recently at a gathering in Luanda, the capital. “We are committed to preserving nature,” she said. What that commitment will mean to reality on the ground is a crucial unknown.

The Boyes team has the blessing of Angolan officialdom, along with international support, to pursue an extraordinarily ambitious study of the Cuito and Cubango Rivers, exploring every mile of them and some of their tributaries, surveying their wildlife, sampling water quality, noting human presence and impacts along the banks, creating a vast and publicly accessible body of data, and trying to comprehend just how the clean waters of southeastern Angola vivify the Okavango Delta in Botswana.

Lifeline to a Desert Delta The waters of the Okavango River Basin flow from Angola’s highlands through the arid Caprivi Strip of Namibia and into the meandering streams of the rare inland delta of Botswana, providing sustenance to unique ecosystems and about a million people along the way. But as pressure to develop once war-torn and remote regions of Angola grows, so does the risk to the sustainability of this oasis. Okavango Expeditions National Geographic–funded scientists have so far completed eight survey expeditions over 4,000 miles by foot, canoe, helicopter, and bicycle, using drones, water sensors, camera traps, and local expertise. The goals: to study endemic species, conduct the first systematic source-to-delta surveys, and inform conservation strategies. A Dynamic Water System Water may be abundant upstream—three times as much rain falls in the highlands as in the delta—but variations in rainfall significantly affect water levels downstream. The dynamic system that’s created nourishes one of the greatest concentrations of wildlife in Africa. mosaic LANDSCAPE The delta swells to life when floodwaters arrive from Angola. Plants and animals—from islands built by termites to meandering channels engineered by hippos, elephants, and buffalo—also regenerate and shape the delta. DEPENDENT DELTA Upstream rivers deliver some 2.5 trillion gallons of water every year. Gentle slopes, grassy floodplains, and absorbent sands slow the Cuito’s journey, while the faster-flowing Cubango has a steeper and rockier descent. Lifeline to a Desert Delta The waters of the Okavango River Basin flow from Angola’s highlands through the arid Caprivi Strip of Namibia and into the meandering streams of the rare inland delta of Botswana, providing sustenance to unique ecosystems and about a million people along the way. But as pressure to develop once war-torn and remote regions of Angola grows, so does the risk to the sustainability of this oasis. Okavango Expeditions National Geographic–funded scientists have so far completed eight survey expeditions over 4,000 miles by foot, canoe, helicopter, and bicycle, using drones, water sensors, camera traps, and local expertise. The goals: to study endemic species, conduct the first systematic source-to-delta surveys, and inform conservation strategies. Cubango Transect The 2017 expedition starts where the faster-flowing Cubango is only a trickle. Source to Sand Megatransect The team begins the 2015 expedition at the highland source of the slow-flowing Cuito. Land mines have killed thousands and injured as many as 80,000 people since 1961—but also have kept headwater habitats relatively untouched. Some 100,000 tourists a year visit safari lodges and camps in the delta area, making tourism one of Botswana’s top industries. Okavango Basin Popa Falls Okavango Basin Okavango Delta Team finishes Cubango transect in June 2017. Sand dunes Highland Source The rainy, forested highlands of Angola provide the surface water that feeds the Cuito and Cubango Rivers and, eventually, the delta below. The heaviest rains fall from October to April and take months to reach the delta’s seasonal swamps. A Vulnerable Wetland With crystal clear water filtered by sandy soils, the wetland is among the world’s most productive and pristine. International, national, and local conservation efforts help keep the delta healthy—as long as water keeps flowing in from Angola. To Lake Ngami A hippo capsizes the team’s canoe–called a mokoro–and pierces its hull. The expedition, once completed, takes six months and covers 1,500 miles, from the highlands to the sands beyond the delta. Team spots its first elephant in Angola. Team arrives at the Andara rapids and islands, sacred burial sites for chiefs of the Hambukushu people. Team continues journey to Makgadikgadi Salt Pans, 159 miles away. NGM MAPS.Sources: John mendelsohn, Research and Information Services of Namibia; NASA; USGS; University of maryland; Okavango Research Institute GIS Lab, University of Botswana; okavango wilderness project; PioTR WOLSKI, University of Cape Town; the Halo Trust; EIS NAmibia; martin gamache, art of the mappable

These survey expeditions, eight so far, have been arduous as well as thorough. The first began on May 21, 2015, when Boyes and his team, traveling with an escort of Land Rovers from HALO Trust, the international demining organization, and a big Russian cargo truck, arrived at the source lake of the Cuito River. They had brought several tons of gear and seven mokoros in which to ferry themselves and their stuff downstream. After paddling the length of the lake on their first day, they discovered that the Cuito at its outlet is a tiny stream, waist-deep but only a yard or so wide, and impossible for navigation by 20-foot-long mokoros. So they dragged the loaded boats downstream, slogging through high grasses alongside the little band of water, pulling like human oxen, and taking data as they went. These mokoros were fiberglass-and-wood models, not dugouts of ebony or some other tree like the Okavango originals, but were still very weighty when fully loaded. They dragged them each day for more than a week before the Cuito became navigable. Then they climbed aboard, with paddles and poles, but faced a new sort of challenge: crocodiles and hippos.

The Cuito along its upper reaches is essentially a wilderness river—clear water, banks lined with reeds, no villages, few signs of humans. On the morning of July 11, 2015, along a broad curve, something plunged through the reeds and into the water just ahead. Boyes, steersman in the lead boat, hollered “Croc,” a relatively routine alert. He ruddered toward the mid-river channel, giving the animal space along the bank.

Suddenly a great bulge of water rose beside Boyes’s boat as a distraught hippo surfaced—probably a young male, Boyes thinks. Turns out the right evasive line for a crocodile is the wrong one for a hippo. Hippos own the deep water. And like crocs, they may kill hundreds of people each year. “It was a big mistake,” Boyes told me later. “Completely our fault. We went right over the animal, defending itself.”

View Images Field observations and a few preserved specimens are emblematic of the diversity of amphibians and reptiles in the rivers flowing into the delta. Through 2016 the expedition surveys had identified 64 reptile and 35 amphibian species in the wider region, including water snakes, lizards, toads, and the darker, yellow-flecked Angolan river frog, which is unique to the country. Photograph by Pete Muller

View Images At dawn in the Angolan highlands, expedition members Götz Neef (left) and Chris Boyes inspect fishnets. So far the team has identified 23 potentially new species Photograph by James Kydd

The hippo drove its lower canine teeth (maybe a foot and a half long, and sharp) through the bottom of the boat. The upper jaw didn’t quite catch the gunwale, so instead of biting the mokoro in half, the hippo just capsized the thing, sending Boyes and his bow paddler, Giles Trevethick, into the water. They clambered onto the hull, and a crew member quickly fired a bear-banger flare, meant to disrupt the attack. Boyes’s younger brother Chris, his expedition chief, in a boat just behind, shouted “Swim!” Boyes and Trevethick got to shore, safe but shaken. Within two hours the boat was patched—using their fiberglass-repair kit—and the expedition was back on the water.

What’s telling from this episode, besides the fast recovery, is how it exemplifies the Okavango Wilderness Project’s harvest of data. From the observations gathered that hour, by electronic device and human eyeball, recorded instantly into an elaborate data-vacuuming system, we know that the Cuito River thereabouts has a strong current, a sandy bottom, and not much aquatic vegetation but harbors smallmouth bream, among other fish. We know that Trevethick made note of a pied kingfisher, then a malachite kingfisher, then a blacksmith lapwing, perched on shoreline limbs. We know the longitude and latitude at which the mishap occurred, to at least 12 decimal points of GPS accuracy. We know that Steve Boyes’s pulse rate (as registered by his Suunto watch, also patched to the system) rose abruptly from 81 beats a minute to 208 beats a minute at 10:57 a.m. And we can assume that 208 is the normal heart rate for a healthy young man trying to outswim the watery gallop of a hippopotamus.

View Images Abhi Mandela, a conservation technologist responsible for uploading expedition data and managing aerial surveys, forces his mokoro through tangled branches on the upper Cubango River. Photograph by Pete Muller

Okavango Expedition A journey into the delta reveals the incredible biodiversity and newly discovered species that could be lost.

When I joined Boyes’s team on the Cubango River, almost two years later, their data-gathering regimen had advanced to include more categories of information. One morning I watched a young Namibian named Götz Neef assess his overnight catch in a fish trap: A largemouth bream, an electric elephantfish of the sort called a Churchill, a squeaker catfish, and more—weird creatures to me, subtle data points of biogeography to anyone who knows African fish. Such sampling and collections, analyzed by ichthyologists allied with the project, will help reveal how the fish fauna of the Cubango differ from that of the Cuito and how both may contain unique species or subspecies, distinct from anything else in the region.

Along the Cuito, for instance, the researchers found what may be a new species of Clariallabes, an eel-like form of air-breathing catfish that seems adapted for wriggling through the saturated peat bogs. Other specialists, based in Angola, South Africa, and England, have also assisted the project with field collections—of amphibians, reptiles, insects, small mammals, plants—and continue the work of identification and analysis. Frogs and dragonflies, with their aquatic immature stages, are sensitive to pollution and can be especially telling as indicators of water quality. One group of peculiar rodents, known as vlei rats in the Afrikaans slang (suggesting that they inhabit transient ponds, or vleis) and notable for the smallness of their territories, seems to have diversified into more than one related species in the highlands.

“Angola is the missing link,” a small-mammal biologist named Peter Taylor, one of the project’s experts, told me, “for understanding the pattern of radiation of these beasts.” Boyes’s goal is to assemble such facts into a mosaic portrait of this two-river system, in its biological and hydrological particulars, to support protecting it for its own sake and the sake of the Okavango Delta.

A Dynamic Water System Water may be abundant upstream—three times as much rain falls in the highlands as in the delta—but variations in rainfall significantly affect water levels downstream. The dynamic system that’s created nourishes one of the greatest concentrations of wildlife in Africa. DEPENDENT DELTA Upstream rivers deliver some 2.5 trillion gallons of water every year. Gentle slopes, grassy floodplains, and absorbent sands slow the Cuito’s journey, while the faster-flowing Cubango has a steeper and rockier descent. mosaic LANDSCAPE The delta swells to life when floodwaters arrive from Angola. Plants and animals—from islands built by termites to meandering channels engineered by hippos, elephants, and buffalo—also regenerate and shape the delta. NGM MAPS.SOURCES: John mendelsohn, Research and Information Services of Namibia; NASA; PioTR WOLSKI, University of Cape Town

Neef, besides trapping fish, also saw to the gathering of water-quality data from two delicate sensors as we paddled downstream. And he saw to the continuous photography—one 360-degree camera on a tripod, plus two DSLRs angled out from the bow of his mokoro, snapping frames at five-minute intervals. In the evenings at camp, as darkness fell, Neef deployed a bat detector, a little yellow box that captured high-frequency blurts of chiropterans, used later to identify the species. Other expedition members recorded data about birds, reptiles, human activity. Boyes himself was the principal ornithologist on the rivers, calling out sightings—giant kingfisher, hammerkop, white-fronted bee-eater, lilac-breasted roller—which a young Angolan biologist, Kerllen Costa, entered with GPS tagging into a tablet. Costa’s sister, Adjany, is an ichthyologist and a National Geographic emerging explorer; also assistant director of the project, she serves as liaison to Angolan officials when she isn’t aboard one of the expedition’s mokoros. Boyes’s team also includes field crew members from Zimbabwe, South Africa, Namibia, the U.S., and of course, Botswana, homeland of his most skilled mokoro boatmen, recruited from the Okavango Delta itself.

Captain of my mokoro was Tumeletso Setlabosha, known to everyone as Water, a small but powerful Wayeyi man who grew up in the central delta. His mother gave him the aqueous nickname because his birth occurred in a pool of water, when she was traveling through the lagoons. Asked his age, Water said he was 54 on land, but “when I’m paddling, I’m 25.” He tolerated me in the bow of his boat for a week, as I gawked and scribbled notes and did my best with the paddle.

View Images The hooves and dung of buffalo churn and fertilize solid ground. In the changeable Okavango, life shapes landscape and vice versa. Picture by Beverly Joubert, NATIONAL GEOGRAPHIC CREATIVE

Human presence along the upper Cubango is sparse, even though the end of the war has allowed people to return to their villages in these southern hinterlands once controlled by the UNITA rebels. Paddling between reed-lined banks, we saw the occasional beached mokoro, the lonely fishing camp, the cow here, the goat there, a few women washing clothes or making moonshine (kashipembe) from jackal berries or other wild fruit in a simple still—and then, farther downstream, more people, more boats, more livestock, corn crops, a soccer field, a few motorbikes. At night, beyond the trill of crickets, we heard the roar of trucks, and the clatter of their springs taking washboard at full speed, on a bad but important dirt track paralleling the river. That road leads to a border crossing with Namibia, through which supplies can roll in and Angolan timber can roll out. Apart from timber and illegal bush meat and water, the Cubango Valley has little to offer the wider world. No one, it seems, has yet found diamonds or gold or oil in this corner of Angola. Clean water: That is the oil and the gold.

One day about noon we beached on the left bank above a small rapid, and because a fully loaded mokoro is too fragile and clumsy for white-water daring, we scouted the line. As we walked, Boyes spotted a hippo snare of stout wire, camouflaged with reed stems and placed along a haul-out path used by the animals. There is nothing more piteous than the howl of a hippo in a snare, he said, and clipped through the wire with his utility tool. Boyes has deep sympathy for the needs of people along the Cubango, and he recognizes that their progress toward better lives must be part of any arrangement for protecting the two rivers, the water flow, the biological riches of southeastern Angola, and the Okavango Delta. But hippo flesh for meat and hippo teeth to be sold as ivory are contraband commodities that the Cubango can’t sustainably surrender.

Another day, we came off the water early to avoid camping near a village called Savate, a place known for the land mines still lurking around its perimeter. We beached upstream, at a dirt landing where it was cow pies, not mines, we had to avoid. Children watched us unload tons of gear—tents and tables and boxes of food, duffels, folding stools, fancy electronics. Women came with piles of washing to this, their regular laundry spot, and had to work around our flotilla of canoes. A tethered donkey grazed nearby. A donkey was wealth. After sunset, by the time our hearty dinner of beans and rice came off the campfire, smelling good, the children had disappeared. I wondered what impression of us they took.

Seen from a Cessna, 500 feet above northern Botswana, the Okavango Delta resembles a paisley carpet of ovals and streaks and patches, gentle rises and swales, a rich pattern textured largely in shades of green and brown. The lagoon waters appear almost black from overhead; the channels and oxbows gleam silver when reflecting a low afternoon sun. At the center of small islands, ringed by trees, lies the whiteness of precipitated salt. Aloft in your little plane, and moving slowly, you get a sense of the dynamic heterogeneity below, of how water has nudged and carved and shaped land over time, opening new channels, closing old ones, rising and falling by season, filling pans, then leaving them to dry, encircling islands, respecting subtle ridges, changing its imperatives and benefices from year to year, and thereby shaping an extraordinary ecosystem hospitable to fish and crocodiles and long-legged birds and mammals that don’t mind having wet feet. That’s how I saw the delta, after my time in Angola, thanks to John “Tico” McNutt, a veteran American conservation biologist.

View Images A blaze sweeps the Cuito floodplain near one of the team’s campsites. Fire is a natural part of grassland and forest cycles, but human-set burns to drive game to hunters exacerbate erosion and siltation. Other upstream threats to the Okavango’s lifeblood include fertilizer and pesticide pollution, river diversion for agriculture, and hydroelectric dams. Photograph by James Kydd

View Images Water from the Okavango River is used to irrigate fields as it flows through Namibia’s narrow Caprivi Strip toward Botswana. Namibia plans to expand agricultural production along the Okavango.

McNutt, a friend of a friend, met me at the small airport in Maun serving Okavango tourism and flew us to the research camp from which he has worked for nearly three decades, studying the endangered African wild dog. With his breadth of curiosity and involvement, he probably understands the ecological and political dynamics of the delta as well as anyone. Besides showing me dog packs on the ground, he gave me four days of eye-in-the-sky perspective and commentary—even while flying the plane and listening for his collared dogs on the VHF telemetry receiver.

On the left, that’s Chief’s Island. On the right, the old Mogogelo floodplain, which once carried water almost all the way to his camp. We gazed down at large herds of lechwe, some reedbuck and impalas, termite mounds rising cream-colored at the center of small islands, hippo tracks like claw marks across the floodplain grasses, elephants casting long shadows in late afternoon. “There’s no vultures,” he remarked. “They should be roosting in these palm groves—should be vultures all over.” But vultures are hated by poachers for giving away the positions of fresh elephant carcasses and are killed by poisoning the left-behind meat. The Okavango, even with the taps open, has its problems.

We flew north across low plains of reeds and papyrus, islands large and small, serpentine channels, until McNutt said: “Somewhere right here would be the fault line, where everything starts to distribute. From the panhandle.”

View Images In her home in Luanda, Lola, her baby, and her cousin Caesar discuss the legacy of decades of war and their hopes for Angola’s future.

The panhandle is a wide stretch of slow-moving water, contained by ridges that rise above swampy lowlands, beginning just south of the Namibia border and flowing southeast to that line McNutt mentioned, known to geologists as the Gumare Fault. Beyond the fault line lies a sunken, flat trough, partly filled with sediments but still nearly the lowest zone in the Kalahari Basin, across which the Okavango waters spread broadly into their flower-blossom shape. The blossom petals come to a dead stop, though, at another pair of diagonal faults, marking the southeastern boundary of the delta. Meeting those natural dams, what remains of the surface water slides westward into a linear lake, Lake Ngami, or sinks away into the sands. South of all this: salt pans and desert.

Amid the complexities of water delivery and biological enrichment, from the headwaters to the delta, from Angola through the Caprivi Strip to Botswana, several factors are especially fateful. The delta itself receives rainfall but not much, and mostly during the summer months of December through March. Angola’s central highlands receive far more, a great wet bounty, roughly 50 inches annually, which saturates the peat deposits and sands of the upper Cuito floodplains and then slowly, after delay, flows down the Cuito and its tributaries. Those rains feed the Cubango too, but the Cubango River catchment lies on steeper, rockier substrate, so the seasonal rainwater comes gushing down fast.

The result of these asynchronies is that the Okavango Delta gets three separate pulses of water annually, giving it a longer and more varied supply of moisture than most freshwater wetlands enjoy. Freshwater coming in pulses, spread across the year, distributed in an ever changing pattern of channels and pans and lagoons, nurturing vegetation of many types, fertilized by the dung of elephants and hippos and impalas—all this is a good recipe for biological fecundity.

View Images Subsistence fishing has long been important to villagers in the Cuito and Cubango watersheds. With better nets, they now get larger hauls and more fish to smoke and carry by motorbike or dugout canoe to area markets. Boyes and others worry that the harvests may not be sustainable.

View Images The Makgadikgadi Pans are flat, salty remnants of an ancient lake, rich with life, that covered much of northern Botswana until faulting diverted the source rivers. Khoisan bushmen now lead tourists here, offering a vision of majestic desolation—and what the Okavango Delta might be without its water.

The biggest challenge faced by the Okavango Wilderness Project is not just to understand this complex system—that’s hard enough—but to persuade Angolan officialdom, and the Angolan people, to preserve the Cuito and Cubango Rivers roughly as they are, flowing free and clean, without much pollution or diversion, through landscapes mostly undamaged by timber harvest, charcoalmaking, forest burning for hunting drives, commercial extraction of bush meat, agricultural schemes demanding high inputs of fertilizer, mining, or other destructive uses. It’s an urgent task and not an easy one.

Some optimists propose that landscapes along the Cuito and Cubango could become international tourism destinations themselves, sites of high-end lodges drawing visitors to see restored populations of magnificent wildlife, such as the Angolan giant sable, that were mostly lost during the decades of war. Maybe such attractions could be included in a regional circuit, they suggest, along with more famous camps in the Okavango. Another hope is that the Botswana government and its tourism industry might recognize the jeopardy of their wonderland—recognize that without the Cuito and the Cubango, there is no Okavango Delta—and act with foresight, offering a compact of payments to Angola for continued delivery of the water. Call it ransom or call it a “water bond” (as Steve Boyes does), it seems rational. Rationality and foresight might be improbable expectations when it comes to intergovernmental relations over resource issues, but the Okavango Delta itself is an improbable phenomenon deserving exceptional concern, imagination, and effort.

Meanwhile the changes in Angola, as Boyes told me, are happening fast. “If we started this work in three years’ time, there’d be nothing left to protect.” The future is coming like a river that flows through other people’s lives.

Contributing writer David Quammen’s new book, on the molecular “tree of life,” will be published by Simon & Schuster in 2018. Cory Richards has photographed nine stories for the magazine. His previous article, “Myanmar’s Toughest Climb,” ran in September 2015.

Society Grant Your National Geographic Society membership helped fund this project.