Home ›› 16 Apr 2022 ›› Opinion
“Bit of a mix-up,” muttered a frustrated Steve Boyes, rustling through the grassy valley that his expedition was approaching its tenth day trekking. “I’ve spent six months looking at satellite imagery, trying to imagine what this place looks like. It’s nothing like what I expected.” Back in 2015, the National Geographic Explorer thought he knew what he’d find when his team of experts in the freshly-formed Okavango Wilderness Project set out from the remote Angolan highlands. In a quest to survey the waters that supply Botswana’s Okavango Delta, the team launched an expedition from the source lake of the Cuito River, which provides water to a large region of downstream southern Africa known as the Okavango Basin. The aim was to see how and where the water flowed. But for the expedition team, the problem was that it didn’t.
Two days after setting off in mokoros (traditional dugout canoes) groaning with equipment, the water dried up. The river that eventually spans five meters (16 feet) from bank to bank was barely more than a stream here—a trickle through a vast, grassy corridor cutting off the Cuito River from its source lake. Harnessed together like huskies pulling sleds, one day of hauling the 400-kilogram (900-pound) dugouts across the land turned into a week. No people, no roads, no rivers. But, realizing just how soft the land was underfoot, a sample of soil turned the expedition’s disaster into one of its most significant discoveries: The land was peat, a dark, boggy substance made from partially decaying vegetation, able to hold 10 times its weight in water. By absorbing rains from the Angolan highlands and slowly releasing them into the rivers of the Okavango Basin, this more than 1,600-square-kilometer (600-square-mile) sprawl of peat deposit has been keeping the entire region saturated year-round. Even if the rains stop, this measured retention means that the rivers farther downstream rarely do.
In their mission to survey how water flows from Angola into Botswana’s Okavango Delta, the expedition ended up discovering the answer to how such a hot, dry region stays hydrated—it has its own natural “water tower.” A system like this―a water tower and the populated downstream basin it supplies―usually only exists in the world’s high mountainous regions, much colder places that hold around half of the world’s freshwater locked up in snow and ice. These mountain water towers are like colossal storage tanks, with snowpack and glaciers acting as the tap. Snow falls, topping up great sheets of ice that drape the mountains, which slowly melt into a steady downstream flow that matters to people and wildlife who need a consistent water supply. The Okavango’s water tower works in the same way, only the mountain is the Bié Plateau, a sand bank elevation high enough to capture rains in the Angolan highlands, which run into a system of source lakes. The peat landscape then acts as the glacier, absorbing that water and releasing it slowly into the rivers in the Okavango Basin.
And just like the 1.6 billion people across the planet that rely on mountains, the people and wildlife across Angola, Namibia, and Botswana need their water tower intact. Not only does the Okavango Delta supply water for over a million people as well as countless species, it could also have a profound impact on climate.
Peat is incredibly carbon rich, formed by decaying vegetation that builds up over thousands of years, absorbing and sequestering carbon dioxide from the atmosphere as it goes. This ability to store carbon is why restoring and protecting the world’s peatlands is considered a vital “nature-based solution” by the UN for mitigating the effects of climate change. As you might imagine, though, if this carbon is released again, the planetary implications would be catastrophic. Peatlands cover around three percent of the Earth, but they hold twice as much carbon as all of the world’s trees. If only a third of these bogs burned, the carbon dioxide in our atmosphere would double.
Until recently, it was believed that most peat carbon repositories were relatively safe within temperate and polar regions of the world, but the peatlands discovered in Angola aren’t. They’re part of an increasingly warm and rapidly developing continent―and slash-and-burn land clearance brings fire ever closer to Angola’s carbon tinder box. This, along with other threats like population growth rate, unchecked commercial agriculture, deforestation, and climate change are all putting the ecosystem at risk.
nationalgeographic
