AN ARK OF TOADS

Nectophrynoides asperginis

On a blazing hot afternoon, Kim Howell sat in his office at the University of Dar es Salaam, crammed with the detritus of forty years of biological research, and plucked a small glass jar from dozens of bottles balanced on a shelf.

"This is it," he said. "It really doesn't look like much."

Floating in the faintly amber liquid was a tiny frog. Brownish skin, pointy nose, it belied nothing significant in appearance. Howell, a kindly white-haired giant with Coke- bottle glasses, had other jars that looked more interesting — floating bats and snakes, each one the subject of his wide-ranging biological curiosity. But perhaps none was so precious as the tiny frog, a species listed on the Convention on International Trade in Endangered Species (CITES) most-restricted list, Appendix I, reserved for rare and critically threatened species of the world, such as rhinoceroses and tigers. He was the first person in the world to discover the tiny amphibian and gave the species its name, Nectophrynoides asperginis, inspired by the Latin aspergo, meaning "spray."

It certainly wasn't the first species Howell discovered. "I found new species of spider, tapeworm, I've had stuff named after me," he said. Among them are a shrew and a subspecies of bird. "What else?" he wonders aloud, trying to reach back through the decades. "A lizard. I think the bird is called a yellow streaked green bull. And then the lizard is called Lygodactylus kimhowelli." What is it like to discover a new species? I asked. "It is exciting when you see something that's new. You don't want to say you're the first person to have seen it before, but nobody has ever described it or photographed it or bothered to say, 'Yes, this one is probably new.'" Nonetheless, he pointed out, the novelty can wear off. "It's fairly normal for a biologist who's working with smaller animals to find new species. If you are an insect person you can find hundreds. Or mites or ticks. If you work on elephants and buffalo the chances are much smaller of course."

Howell's office at the University of Dar es Salaam feels like a universe away from Pittsfield, Massachusetts, where he was born and raised. His ticket out of the small industrial town was an acceptance letter to Cornell University, where he paid for his degree in vertebrate zoology by working in the school's Laboratory of Natural Sound, preserving archival recordings of birdcalls collected in Africa during the early twentieth century. After four years, Howell wanted nothing more than to go to Africa himself, though the Vietnam War also played a role. As a conscientious objector, he needed an alternative service approved by the American government. In 1969 he chose a "wild card option in the middle of nowhere Zambia" where he taught science at a remote elementary school. At the end of that first year, he traveled north to Tanzania where he worked at a school for children of South Africa's apartheid refugees before deciding to stay for good. Howell has lived in Tanzania ever since, raising a daughter with his wife and teaching at the university.

In the early 1990s, Howell was looking through a local newspaper and took note of an unusual ad for employment. Placed by an agency called Norconsult, a Norwegian engineering firm, the ad was soliciting environmental consultants. "There was this hydropower project that was going to be done, and they were looking for someone to look at birds," said Howell. "The location was so far away, I'd never been there. I didn't even know where it was." Howell decided to write to the company but didn't hear anything back for nearly two years. Then, seemingly out of the blue, a man walked into Howell's office and asked if he was interested in doing some studies related to a hydropower dam in the Udzungwa Mountains, one of the southernmost areas of the Eastern Arc Mountains. "I said, 'Sure.' How often do you go someplace no one's ever been to before and get paid for it?" recalled Howell.

In those days the journey from Dar es Salaam to the Udzungwa Mountains took a full day on a dirt road that roughly paralleled the rail lines of the Tanzanian-Zambian railroad, an early development project by the Chinese in Africa laid down in 1968. Villagers in the region use the train tracks as a footpath through the banana trees, sugarcane fields, and lush floodplains of the Kilombero Valley. The Eastern Arc Mountains are made up of basement rock from the Precambrian eon, some of it dating back 3.2 billion years. Around 30 million years ago, the crust fissured, cracked, and faulted, and pushed the rock into the form of a crescent-shaped mountain range cambering through East Africa. The uplift separated the Arcs from the main Guineo-Congolian forest of west and central Africa, birthing a kind of archipelago of primeval forest that was kept stable by consistent temperatures and high rainfall from the nearby Indian Ocean.

The mountain range is sometimes called Africa's "Galapagos Islands" because there are thirteen mountain "islands," each with their own unique variations of species and habitat but part of the same original geological event and climate. Each of these islands became a laboratory of natural selection by virtue of its isolation, giving rise to unique trajectories of species and an endemism unrivaled in the world. Biologists today have recorded ninety-six vertebrates and over 800 endemic plant species (including thirty-one species of African violet alone) in the Arcs. The stability of the climate may also have reduced the rate of extinction, which scientists determine by the number of genetically ancient species they find present in the forests. DNA analysis of some forest birds in the Eastern Arcs shows lineages stretching back to the early Miocene epoch some 20 million years ago. Much of the fauna reveals a greater connection to Madagascar than continental Africa, with other birds showing commonality with subspecies originating in Southeast Asia — back when a single continent called Pangaea covered the globe.

Deep in the Udzungwa Mountains, a river of water cut through the forest and over a steep gorge, creating a plunging waterfall. From top to bottom, the gorge is roughly two miles long and drops nearly 3,000 feet. Unlike nearly every other river and stream in Tanzania, what became known as the Kihansi River didn't shrink during the dry season. Twelve months of the year, the waterfall inside the gorge was so powerful that the cascades could be seen from miles away against the thick verdant rainforest — majestic...