National Geographic : 2017 Nov
86 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 ele- phants, hippos, crocodiles, and wild dogs; lechwe and sitatungas and other wetland antelopes; wart- hogs and buffalo, lions and zebras, and birdlife of wondrous diversity and abundance—not to men- tion a tourism industry worth hundreds of mil- lions 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 be- neath 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. 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 south- east, 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 Ango- lan 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 hip- pos, 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 south- eastern Angola—in land use, water diversion, population density, and commerce—make this dark prospect a real possibility. That’s why the By David Quammen Photographs by Cory Richards n Society Grant Your National Geographic Society membership helped fund this project. 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.