“It's like a land mine going off below you. You just go flying,” says wildlife biologist Steve Boyes. He and his research assistant had just been thrown from their dugout canoe by an angry hippopotamus. Both of them landed on top of the animal, in the water, then quickly scrambled atop the hull of the overturned boat. “And we're looking at each other, and he's thinking the same as me, ‘just get your legs out of the water,’ imagining clamping jaws.” Both men managed to swim to the bank unscathed, but the two giant tusk holes pierced through the bottom of their canoe left a sobering reminder of what could have happened.

When the incident occurred, the 36-year-old National Geographic emerging explorer and his team were one month into a four-month, 1,578-mile expedition down the Cuito and Okavango Rivers. Along the way, they would collect baseline data, with the eventual goal of turning the river itself and the adjacent forests and floodplains into Africa’s largest wildlife reserve in an unprecedented international conservation effort that would ensure the preservation of the entire Okavango catchment.

The largely unexplored Cuito is one of the two main rivers that flow into the Okavango River and feed the Okavango Delta, which Boyes describes as “the beating heart of our planet.” The pristine, 10,000-square-mile wetland basin sprawls across the borders of Botswana, Namibia, and Angola. It shelters the largest remaining population of elephants, as well as populations of some of the world’s most endangered mammals, such as cheetah, white rhino, black rhino, African wild dog, and lion. It’s also home to large populations of hippo, buffalo, red lechwe, zebra, leopard, hyena, and crocodile. After Boyes first visited the delta in 2000, he decided to move there full-time, begin work on his Ph.D., and dedicate his life to fight for its protection.

In 2010, the South African Boyes enlisted the help of French cameraman Jerome Hillaire and two native Ba’Yei or “River Bushmen,” and made the first documented journey across the Okavango Delta. That first trip spurred an annual tradition, and, each subsequent year, Boyes has led a 15- to 18-day expedition across a different 200-plus-mile section of the delta to gather data with an ever increasing team of scientists, photographers, and Ba’Yei guides. In 2014, due in part to Boyes’s research and advocacy, UNESCO declared the Okavango Delta a World Heritage site, which protects the land indefinitely from agriculture and extractive industry.

But, so long as the rivers that feed the delta remain unprotected, the Okavango Delta itself is at risk. For 35 years, war in Angola made the Cuito River essentially inaccessible. Now, more than a decade after the end of the war, the river faces threats of proposed dams and slash-and-burn agriculture. This past May, with the support of a National Geographic Expeditions Council grant, Boyes launched his expedition down the Cuito, his largest yet. The team of 31, including several multidisciplinary emerging explorers, set out to travel from source to delta. Throughout the four-month journey, the team broadcasted, in real time, everything from their individual heart rates to their location, land surveys, photographs, and data on water quality and animal species.

The trip got out to a tough start. After a nine-hour drive through forests and across three minefields leftover from the war, the team reached the remote lake at the source of Cuito only to find that the river, that far upstream, lacked a channel large enough for their 19-foot, flat-bottomed makoro canoes to pass through. The team spent the first nine days harnessed to their makoros, each of which weighed over a thousand pounds, dragging the seven boats over dry land. Some days, they made only a mile of progress. The team had budgeted 19 days for the first 375 miles of their journey. It took them 48 days.

Despite the setbacks early on, Boyes and his team made it to the delta on September 18, 2015. They succeeded in collecting the data they had wanted and, in addition, discovered eight new species of fish and two possible new mammal species. In 2016, Boyes will return to the Cuito for six shorter expeditions to conduct more targeted biodiversity surveys and to continue to work to protect the Okavango Delta. With support from a National Geographic Expeditions Council grant, his story will appear in the November 2016 edition of National Geographic magazine.

“This is one of those last chances to save a wild river, the last chance to save the elephants, the last chance to save the last wetland wilderness in Africa—or in the world,” says Boyes.

—Jen Altschul

THE INTERVIEW

Adventure: Do you know why that hippo decided to flip your boat?

Steve Boyes: It was totally right in what it did. When a hippo rushes out from a shallow area in the reeds, you go straight at where it came in, and allow him to go to the deep water. I thought it was a crocodile, and I basically followed him to the deep water. He would have assumed that we were hunting him or—I don't think he could figure out why the hell we were trying to get straight on top of him. These animals in wilderness areas who don't interact with people that much are really not out to get you. In fact, they're trying to respectfully get away from you. It was our fault.

A: Why is it important to broadcast the data in real time?

SB: We literally only have two years. So, gathering all of this scientific data and hiding it at a university to publish it would be counterproductive. That is the world we live in now. We can't be conservationists and hide away with any kind of data, because action has to happen now. If you can be, you must be live. You must literally provide this information in real time. That's how urgent it is.

A: Does tourism pose a threat to the Okavango?

SB: Tourism is not a threat, it's the solution. The Angolans are in a developing country. They've just seen the oil price cut in half. They're looking now at diversifying their economy, and tourism could bring in a lot of dollars. There is the potential to establish the largest wildlife reserve in Africa, and it will have to have tourism development as the economic driver for that region. It's our only chance. That's the only way we can add value to that landscape.

A: You call the Cuito River one of the least known places on Earth. Why do people know so little about it?

SB: People, over all time, have not lived there, because it's very difficult. It's a nutrient-deficient environment. Animals struggle to live there. The people that have come in there only arrived in about the 1970s. Before that, it was hunter-gatherers of very low densities ... The people that we met had never seen anyone from the outside world.

A: What makes the Okavango special?

SB: There's a connection to eternity. It's wilderness. It's a wild place that is the representation of millions of years of natural selection and evolution and balance within that system ... It is that perfect ... It is the wildest place in Africa remaining now.