Before New York

When Henry Hudson first looked on Manhattan in 1609, what did he see?

Of all the visitors to New York City in recent years, one of the most surprising was a beaver named José. No one knows exactly where he came from. Speculation is he swam down the Bronx River from suburban Westchester County to the north. He just showed up one wintry morning in 2007 on a riverbank in the Bronx Zoo, where he gnawed down a few willow trees and built a lodge.

"If you'd asked me at the time what the chances were that there was a beaver in the Bronx, I'd have said zero," said Eric Sanderson, an ecologist at the Wildlife Conservation Society (WCS), headquartered at the Bronx Zoo. "There hasn't been a beaver in New York City in more than 200 years."

During the early 17th century, when the city was the Dutch village of New Amsterdam, beavers were widely hunted for their pelts, then fashionable in Europe. The fur trade grew into such a lucrative business that a pair of beavers earned a place on the city's official seal, where they remain today. The real animals vanished.

That's why Sanderson was skeptical when Stephen Sautner, a fellow employee at WCS, told him he'd seen evidence of a beaver during a walk along the river. It's probably just a muskrat, Sanderson thought. Muskrats are more tolerant of stressful city life. But when Sautner and he climbed around a chain-link fence separating the river from one of the zoo's parking lots, they found José's lodge right where Sautner had said it was. When they returned a couple of weeks later, they ran into José himself.

"It was just getting dark," Sanderson said. "We were standing on the riverbank shooting the breeze, when all of a sudden we saw the beaver. He swam right up to us, then he started doing circles in the river. We backed up a little, and he did that beaver alarm call with his tail, slap, slap against the water. So we decided we'd better take off."

The beaver's return to the Big Apple was hailed as a victory by conservationists and volunteers who'd spent more than three decades restoring the health of the Bronx River, once a dumping ground for abandoned cars and trash. José was named in honor of José E. Serrano, the congressman from the Bronx who'd pushed through more than $15 million in federal funds over the years to support the river cleanup.

For Sanderson, José's story meant something more. For almost a decade he has led a project at WCS to envision as precisely as possible what the island of Manhattan might have looked like before the city took root. The Mannahatta Project, as it's called (after the Lenape people's name for "island of many hills"), is an effort to turn back the clock to the afternoon of September 12, 1609, just before Henry Hudson and his crew sailed into New York Harbor and spotted the island. If people today could picture what a natural wonder Hudson had looked upon, Sanderson figured, maybe they'd fight harder to preserve other wild places. "I wanted people to fall in love with New York's original landscape," he said. "I wanted to show how great nature can be when it's working, with all its parts, in a place that people normally don't think of as having any nature at all."

Long before its hills were bulldozed and its wetlands paved over, Manhattan was an extraor­­­dinary wilderness of towering chestnut, oak, and hickory trees, of salt marshes and grasslands with turkey, elk, and black bear—"as pleasant a land as one can tread upon," Hudson reported. Sandy beaches ran along stretches of both coasts on the narrow, 13-mile-long island, where the Lenape feasted on clams and oysters. More than 66 miles of streams flowed through Manhattan, and most of them sheltered a beaver or two—making José's appearance, in Sanderson's eyes, a rare glimpse of the way things used to be.

"You might find it difficult to imagine today, but 400 years ago there was a red maple swamp right here in Times Square," he said one day not long ago, as he waited for the light to cross Seventh Avenue. Dressed in black jeans and a Windbreaker, he didn't look much different from the tourists beside him on the curb. But unlike them, in his mind he was following a trail along a swampy creek that disappeared beneath the entrance to the Marriott Marquis Hotel at the corner of Broadway and West 46th Street. "Just over there was a beaver pond," he said, as a bus rumbled by. "It would have been a good place for deer, wood ducks, and all the other animals associated with streams. Brook trout probably, as well as eels, pickerel, and sunfish. It would have been much quieter, of course, although today's not so bad."

Sanderson conceived the Mannahatta Project one evening in 1999, after buying a coffee-table book of historical maps of the city. A recent transplant to New York from northern California, he was curious about how the city had evolved. "The landscape in Manhattan is so transformed, it makes you wonder what was here before," he said. "There are views in this city where you cannot see, except for a person or maybe a dog, another living thing. Not a tree or a plant. How did a place become like that?"

One map in particular caught his eye: a beautifully colored print from 1782 or 1783 that showed the hills, streams, and swamps as well as roads, orchards, and farms on the entire island—something no other contemporary map had done. More than ten feet long and three feet wide, the map had been created by British military cartographers during the eight-year occupation of New York during the American Revolution. Later called the "British Headquarters Map," it showed the island's topography in unusual detail because British officers needed that information to plan their defense of Manhattan. To Sanderson the map presented a unique opportunity to strip away the city's skyscrapers and asphalt and look at least partway back to the island's original landscape.

What would happen, he wondered, if he laid a street grid of today's city over this 18th-century rendering? Would anything line up? To find out, Sanderson enlisted family and friends, starting with his wife, Han-Yu Hung, and their young son, Everett, to join him on weekend expeditions to visit places on the map that still existed. Trinity Church in Lower Manhat­tan, for one, was founded in the late 17th century. A typical grave marker in the church cemetery reads, "Here Lyeth the Body of John Abrell Who Departed this Life Jan the 10th 1762 Aged 40 Years." Since the cemetery can be located on both the "British Headquarters Map" and today's street grid, Sanderson was able to push a virtual pin, so to speak, through both maps by taking a GPS reading at the site and attaching it to a digitized version of the older map. After repeating this process at 200 or so places, sticking in pin after pin, he and his team succeeded in matching the "British Head­quarters Map" to today's city grid with an accuracy of half an uptown block, or roughly 130 feet. For Sanderson this added a whole new dimension to the modern city's landscape. He could now stand at any spot in Manhattan and picture, more or less, what had been there in 1782.

Take the gentle rise of Fifth Avenue as you walk past the New York Public Library. "There's a reason you can stand on the sidewalk here and see the tops of people's heads a few blocks away," Sanderson said. "This was near the top of Murray Hill, where the Murray family had a farm and orchard in 1782. During the battle for New York, the British landed at Kips Bay on the East River and marched up here, cutting off half of Washington's army, which was trapped in Lower Manhattan. There's a legend that Mrs. Murray offered tea to the British officers. So they stopped here at the farm, and while they were having tea, Washington's troops slipped past them on the Bloomingdale Road, which is now Broadway, and escaped."

As fascinating as the "British Headquarters Map" was, Sanderson didn't want to stop his time machine at 1782. He wanted to go all the way back to 1609. So he and his colleagues stripped from the map all the features that had been added by settlers and soldiers—such as roads, farms, and fortifications—until they'd reduced their digitized version of the map to the basic building blocks of the physical landscape: shorelines, hills, cliffs, land cover, streams, and ponds. As a landscape ecologist, Sanderson was used to taking apart wild places conceptually to understand how they work, separating a rain forest in Gabon, say, into geological, hydrological, ecological, and cultural layers. Now he and his colleagues set out to build a landscape from the bottom up, starting with the terrain and filling it with all the plants and animals that were likely to have lived there.

They began by listing the various ecosystems they could safely assume existed on the island, such as old-growth forests, wetlands, or plains, based on soil types, rainfall, and so on. Because it was located at the intersection of geographic regions, Manhattan probably had not only spruce trees from the northern forests but also magnolias from the southern forests, migratory birds from nearby flyways, and even tropical fish from the Gulf Stream during summer. In all, they identified 55 different ecological communities. "It was an incredibly diverse place," Sanderson said. "If the island had stayed the way it was back then, it could have become a national park like Yosemite or Yellowstone."

Once they identified the island's ecosystems, they could fill in the wildlife. But which animals lived where? To be as precise as possible, Sanderson's group took their research a step further. For each species they identified essential habitat requirements. A bog turtle, for example, needed a wet meadow, insects, and a sunny place to warm itself, while a bobcat needed rabbits and a den site in which to raise its young. "We just kept asking ourselves, What does this need? What does this need? What does this need?" Sanderson said. Then they compiled a list for each species. As they built their database, they discovered a dense network of relationships among species, habitats, and ecosystems on the island, not unlike the complex social networks that people create. Sanderson called this network a Muir web, after American naturalist John Muir, who once noted that "when we try to pick out anything by itself we find that it is bound fast by a thousand invisible cords that cannot be broken, to everything in the universe." Sanderson and his team, in a sense, were trying to make those thousands of cords visible.

Consider a beaver that lived at Times Square in 1609. If you grabbed him by the scruff of his neck and lifted him out of the web, you'd find lines connecting him to a slowly meandering stream, to the aspen trees he ate, and to the mud and twigs he used to build a lodge. Not only that, you'd also find lines to the bobcats, bears, and wolves that depended on him as prey and to the frogs, fish, and aquatic plants that lived in the pond he helped to create. "The beaver, it turns out, is a landscape architect, just like people," Sanderson said. "You need him to flood the forest, which kills the trees that attract the woodpeckers that knock out cavities that wood ducks use for shelter." Lifting a beaver out of the web disrupts scores of other residents, which demonstrates how important it can be to think about an ecosystem as a network.

By the time Sanderson and his team had finished compiling their database, they'd put together one of the most detailed scientific recon­structions of a landscape ever attempted, identifying 1,300 or so species and at least 8,000 relationships linking them to one another and their habitats. This was somewhat ironic, San­derson admitted, since it described a place that didn't exist anymore. But the same methods that created a portrait of Mannahatta could be applied to wild places today, such as the Greater Yellowstone region, the Congo forest, or the eastern steppes of Mongolia. If scientists have a model of how a landscape and species interact, they can better predict the impact of climate change, hunting, or other disruptive factors.

For the Mannahatta Project, the next step was to turn all of these data into realistic 3-D scenes, like the one you see at the top of page 122. Sanderson's goal, from the start, had been to show what any spot in today's city—say, the taxi stand on Seventh Avenue in front of Madison Square Garden—looked like 400 years ago. (It was a marsh at the edge of a forest.) To make that happen, Markley Boyer, a visualization specialist, used 3-D modeling software to populate each digitally created scene, block by block, with the right mix of oaks, hickories, streams, ponds, and marshes according to the Muir web database. "We're basically using the same kind of 3-D software they use in Hollywood to create digital armies marching across a plain," Boyer said, "only we're generating tens of thousands of trees in appropriate proportions for each forest type." Visitors to can give the time machine a try by entering any address in Manhattan to see what that block looked like way back when.

As New Yorkers this month mark the 400th anniversary of Hudson's visit, Sanderson hopes his project, which has grown to include more than 50 historians, archaeologists, geographers, botanists, zoologists, illustrators, and conservationists from the WCS and other institutions, will stimulate a new curiosity about what existed on Manhattan before the explorer arrived. "I'd like every New Yorker to know that they live in a place that had this fabulous ecology," he said. "That New York isn't just a place of fabulous art, music, culture, and communications, but also a place of amazing natural potential--even if you have to look a little harder here."

Peter Miller is a senior editor. Robert Clark's photographs of Angkor appeared in the July issue. This is the first time that work by Markley Boyer or Philip Straub has been published in the magazine.