The Okavango wilderness gives up its most vital secrets

When the rains sweep across southern Africa each year in October, rivers feeding the Okavango Delta flood their banks and wash over a roughly 11,000-square-mile area. This vast, swirling labyrinth of islands, marshes, and waterways in the Kalahari Desert links three countries—Botswana, Namibia, and Angola—supporting thousands of plant and animal species, along with the Indigenous communities who have depended on it for millennia.

Much about life within the Okavango has remained a mystery because of the sheer difficulty of navigating this ever-changing waterscape. Many areas are off-limits owing to local taboos and unexploded land mines left behind from Angola’s nearly 30-year civil war. Even the source of the delta’s rivers, reputedly in the remote highlands of Angola, eluded European explorers and mapmakers for centuries.

There are no glaciers there. No snowcapped peaks or ice caves. That absence presented a puzzle that’s only grown in ecological importance as temperatures across the continent have continued rising: How was it possible that the delta flowed freely year-round, even through the long dry season?

Over a decade ago, an international group of conservationists, government officials, and scientists came together to seek some answers. With support from the National Geographic Society, they founded what would become the Okavango Wilderness Project. Their goal was twofold: to understand and protect the true source of one of Africa’s largest freshwater ecosystems and to document the life it supports. Along the way, they improved their techniques by constantly innovating how they traveled and conducted research, creating an expansive tool kit that could inspire more breakthroughs.

For conservation biologist and National Geographic Explorer Steve Boyes, the team’s leader, one key was adopting the right mode of transport: Boyes had already been conducting bird surveys in the delta for years, so he knew to insist on flat-bottom canoes known as mokoros, the time-tested means by which local people navigate those shallow, reed-choked channels to fish and hunt wild game.

(Steve Boyes traces life to its source in the Angolan highlands.)

Though mokoros are traditionally hewed from tree trunks, the team’s standard fiberglass models allowed them to carry hundreds of pounds of food and scientific gear while skimming across the water. But during their first launch, on a lake in the Angolan highlands in May 2015, an unexpected challenge emerged. Almost immediately, they hit peat. “We realized, well, there’s no water for us to paddle on,” recalls Götz Neef, a research manager on the team. “We carried on basically pulling our mokoros for the first 10 to 15 days.”

It was the first of many hard lessons. By the time they dragged their boats off the water in Botswana after 121 days in the field, they’d covered 1,500 river miles and added a new item to their equipment list: several sled harnesses to help them haul their boats across the unpredictable terrain.

They also added a new fish species to the global inventory. The first net that the team dipped into the lake brought up a climbing perch with a striking checkerboard pattern, a nocturnal species that was unknown to modern science. (In 2021, scientists named it Microctenopoma steveboyesi in honor of the expedition leader.)

Since that first trip, the scientific investigators have returned to the Angolan highlands more than a dozen times, completing six other months-long megatransects of several thousand miles, along with more focused surveys and environmental and biological sampling efforts. With each expedition, they have not only refined their preparation and equipment but also updated their research methods.

Some water-quality measurements that once required a laboratory can now be made in real time in the field, while a 360-degree camera mounted on the bow of a mokoro captures panoramic images every 60 seconds to produce maps. The team still uses binoculars out in the field and nets to sample fish and aquatic insects, but they’ve also trialed more sensitive tools, such as 3D-printed spheres that are placed in water to collect genetic traces of organisms, mainly from their tissue and waste, offering a hint at what might lie below the surface. So far, they have identified more than 70 species in water and on land that are new to science, including a bizarre tarantula with what looks like a deflated horn on its back, and hundreds of potentially new species, among them an antelope that needs further research.

Everyone on the team has brought a different set of talents. For instance, boatmen from Botswana were accustomed to slapping their paddles against the water’s surface to scare hippos away. In Angola, that tactic only made the dangerous animals more aggressive. “They attacked us three times in two days,” says Kerllen Costa, the project’s Angola country director and a National Geographic Explorer, of one early trip. Finally, an Angolan team member spoke up, explaining that local hippos responded better to silence. From that point on, the attacks stopped. The team won’t even say the word “hippo” out loud now, Costa explains, in accordance with local customs.

As the baseline snapshot of the region’s biodiversity has come into focus, the project has started tracking how the system is changing under climate pressure and human use. Fish have grown scarce in some areas due to overharvesting, and team members have been working to create protected reserves to help rebuild their populations.

The team’s measurements have uncovered other long-term concerns as well. When the vegetation turns to a crisp in the longer dry seasons, herders move their cattle right up to the riverbanks to reach fresh greenery. Over the years, the Kavango River in Namibia, which feeds the delta, has grown murky from erosion and the destruction of the papyrus beds.

Once the water moves downstream, however, it passes through almost 40 miles of papyrus that acts as a natural filter, purifying it before it fans out across the heart of the delta. “How much can these papyrus beds take before they break down or stop working?” Neef asks. It’s a question the researchers are still trying to figure out, though they have come to realize that the future of the delta will ultimately be decided far upstream.

As for the central mystery that brought them to the highlands in the first place, Boyes recalls discovering an important clue during their initial expedition. On satellite images, the team had spotted depressions in the high valleys that appeared to be little more than grassy patches of land, perhaps seasonal wetlands. Once they arrived in person, the team members realized they had found a mosaic of previously undescribed peatlands—giant subterranean sponges of ancient plant matter—that swell each rainy season and then slowly release their water into these scattered depressions and on to the lowlands.

In Scotland, such peat bogs would be unremarkable, but no one expected such an extensive network in a mountain valley in Africa. A few years later, in April 2017, Boyes brought along scuba gear to explore life underwater in these eerie blue-and-green source lakes. “It’s like diving in a lake on a moon of Saturn,” he says. “It’s not on this Earth.”

But it would take time for researchers to truly understand the magnitude of the peatland discovery. In 2019, Boyes came across a study that described mountains as “the water towers of the world” because of all the water stored in their ice and snow. He liked that description but was dumbfounded to see that a global map of those towers left Africa entirely blank. It represented a yawning gap in our understanding of the continent’s watersheds.

Three years later, the team invited Mauro Lourenço, then a Ph.D. student at the University of the Witwatersrand in Johannesburg, South Africa, to take a core sample of the marshland. Driving a six-foot steel soil sampler into the ground, Lourenço was startled to find that it didn’t go deep enough. The entire column was pure peat. When he returned with a longer tool, he discovered that the peat extended more than 12 feet down in some areas. Lourenço now estimates that the highlands capture over 100 trillion gallons of water, the equivalent of 170 million Olympic-size swimming pools.

With the help of remote sensing, field sampling, and repeated expeditions, Lourenço and his colleagues have mapped out the boundaries of what they have dubbed the Angolan Highlands Water Tower, which is sustained by peat, not ice. They believe this could be the first of many such systems that exist across the continent.

The Angolan water tower recently became the country’s first ever Wetland of International Importance under a global treaty known as the Ramsar Convention on Wetlands, which will help encourage more formal protection and management. Its official name, in the local language of Luchazi, is now Lisima Lya Mwono, or “Source of Life.”

Today the team’s mission has evolved from discovering more about that source to gathering information that may inform important ways it can be preserved. At the same time, Boyes and other team members are already exploring new territory. They’re working with partners to apply the research techniques they developed in the Okavango throughout Africa to identify and study more water towers supporting the continent’s great river basins.