In a clearing in rural Somalia, a jihadi commander sat in a white plastic chair, stroking a dik-dik, an antelope the size of a cat. His men escorted two British journalists into the clearing and sat them under an acacia tree. The commander, who had offered safe passage and a rare interview, released the dik-dik, which scuttled off into the bush.

Dik-diks are hard to catch but easy to shoot, and for this reason one of the journalists, Jonathan Ledgard, who was the East Africa correspondent for The Economist, later described the battle against these jihadis, known as the Shabaab, as “the dik-dik war.” The commander began a lecture on the supremacy and fairness of Islamic law, jabbing his finger at the sky. But Ledgard barely noticed; he was looking at the array of mobile phones that the commander had laid out in front of him. It was 2009; the digital world was becoming enmeshed with the physical world, accessible in a place where the environment could hardly sustain human life. “You could receive money through a wire transfer, but you could not keep your child alive,” Ledgard later wrote. He realized that nothing the man had to say—nothing that anyone had to say about the conflict—was as essential to understanding the transformation under way in the region as the fact that the phones had perfect reception.

For fifteen years, Ledgard had been reporting on war and disaster in Latin America, the Balkans, Afghanistan, Central Asia, and Africa, while writing novels to settle his mind. He carried two notebooks—red for his reporting notes, blue for thoughts and observations to use in fiction. With each journalistic assignment he grew more interested in the contents of the blue notebooks, and less sure that reporting on the world’s horrors did anything to change them. “I had been looking at the world as if it were cracks in a pavement,” Ledgard told me. “But it’s not about the individual cracks, it’s about the patterns and the networks,” the scale of which eluded the dispatch format.

The world was undergoing an accelerating convergence of technological and environmental trends—you could feel it in Nairobi, Kenya, where Ledgard lived. A little more than a century earlier, the city hadn’t existed; now it had a population of millions, doubling in size every generation, and was home to perhaps the largest urban slum in Africa. “The biggest risk for Africa is the unmet expectations of its youth,” Ledgard wrote, years later. At least fifty per cent of the continent was less than twenty years old. It was the best-educated generation in African history, digitally connected to the rest of the planet, yet the World Bank estimated that seventy-five per cent of sub-Saharan youths would be unable to find a salaried job in the coming years. “They will be easily knocked flat by mishaps or illnesses,” Ledgard continued, and would be prone to recruitment into insurgencies and terrorist groups. It was no coincidence, he thought, that the jihad was most active in the areas already being ravaged by oil extraction and climate change.

New technologies were lifting a nascent class of entrepreneurs and activists, but also enabling predatory regimes to crush them. “Africa rising” was the phrase often heard at conferences in Geneva and New York; “Africa wavering” was Ledgard’s view. Decades of humanitarian aid had not slowed the proliferation of refugee camps, or the surge of migrations across the desert and the sea. Meanwhile, the pace of human development was destroying the natural world faster than scientists could catalogue its systems, much less understand how they fit together. “You don’t have to be a C.I.A. analyst to realize that it doesn’t add up,” he said.

Ledgard saw a brief window for radical changes in sustainability and governance—a couple of decades, perhaps. After that, it seemed clear that no previous conflict or migration would compare to the hell to come. Feedback loops would be set in motion that would transform the earth into an irradiated planet. Already, humans are expected to force more than a million species into extinction, and, by 2050, to fill the oceans with a greater mass of plastic than there is of fish. In interviews, Ledgard started pressing politicians, consultants, businessmen—anyone with power—to devise strategies for a more equitable, sustainable future. “But I just wasn’t getting any answers,” he told me.

The most exciting thinking about the near future was taking place on the fringes of the tech sector, among people who worked on networks and artificial intelligence. “There is no room for techno-utopianism in our bare-fisted future,” Ledgard wrote. But if there were a way to counter the scale and pace of human depredations, he thought, it would come out of the laboratories and companies whose creations were enabling it.

In 2012, Ledgard quit his job, moved to Switzerland, and began a fellowship at the École Polytechnique Fédérale de Lausanne, one of Europe’s best research institutes. “It was very important to me to be in an almost autistically scientific environment,” he said—not “hanging around with political scientists or economists or anthropologists and having the usual conversations, learning nothing.” He pinned photographs of a Nokia 1100 and a Kalashnikov next to his desk, as reminders of why he was there.

For the first two years, Ledgard sat through hundreds of lectures by theoretical physicists, computer scientists, mathematicians, and engineers, and forced himself to read abstracts of scientific and philosophical papers on subjects that he could barely grasp. “My brain started moving in these completely different and much richer directions,” he said, sparking “a series of progressive realizations that the world that I thought I understood is not at all the world as it is.”

In time, Ledgard refashioned himself as both an evangelist of radical thinking and a prophet of specific doom. He won’t tell you that the world is ending; he’ll just present the charts that show you how. “The only possible thing to do is to go in an imaginative direction,” he told me. “Imagination at scale is our only recourse.” This approach has led him into collaborations with an array of famous partners—the British architect Norman Foster, the Danish-Icelandic artist Olafur Eliasson—on projects that range from practical and humanitarian to fanciful and abstract. The world, according to Ledgard and his collaborators, might stand a chance if cargo drones delivered goods in the roadless areas of East Africa; if sentient robots were curious about the natural world; if people could immerse themselves in the sights and sounds of the deepest parts of the ocean; if plants and animals could pay people for the cost of their preservation. “I’m not sure if this is a real project or I’m trying to write a novel in the natural world,” Ledgard told me, referring to the last of these ideas.

Ledgard knows how fantastical his projects can sound. “You have to acknowledge that the probability of success is vanishingly small,” he said. “But if just one of these ideas came off in the next twenty years, in some form, and in a really significant way—and it improved the lives of poor people, or helped save other life-forms from extinction—then that would be really worth your time.” He added, “My main point is to move the conversation in a more imaginative direction.”

Outside a Czech village, Ledgard searched for wild boar, which he is studying for an immersive art exhibit. Photograph by Rafal Milach / Magnum for The New Yorker

“You get visionaries, you get dreamers, but Jonathan is also a realist, and intensely practical,” Norman Foster told me. “Perhaps that’s why there has been so much common ground between us. In the end, architecture is projecting imagination to realize a tangible project.” Each of Ledgard’s projects appears to be animated by a single question: What if human greed could be harnessed as a kind of natural resource, and redirected to mitigate its own effects?