NEW YORK (NYT NEWS SERVICE).- Before the first Dutch colonists sailed through the Narrows into New York Harbor, Manhattan was still what the Lenape, who had already lived here for centuries, called Mannahatta. Times Square was a forest with a beaver pond. The Jacob K. Javits Federal Building, at Foley Square, was the site of an ancient mound of oyster middens.

Eric W. Sanderson is a senior conservation ecologist for the Wildlife Conservation Society, based at the Bronx Zoo. In 2009 he published “Mannahatta: A Natural History of New York City.” The book geolocated old maps onto the modern city to reimagine a cornucopia of hills, beaches, fields and ponds.

This is the latest in a series of (edited, condensed) virtual walks with architects and others. I spoke with Sanderson by phone. Our “stroll” explored lower Manhattan. We “met” where the Staten Island Ferry docks at Whitehall Terminal.

Except that we imagined it was the September afternoon in 1609 when Henry Hudson arrived, and we were standing near the shore, gazing at the water.

Michael Kimmelman: Aside from Hudson’s ship, what do we see?

Sanderson: Whales and porpoises. One of the earliest sketches we have of Manhattan shows a whale in the Hudson River. The charter of Trinity Church includes a provision specifically saying dead whales found on beaches in the province of New York are property of the church, which could use them to make oil and whale bone. So whales were clearly a meaningful part of the local economy and ecosystem.

Kimmelman: What was the ecosystem?

Sanderson: Ecosystems, actually. Manhattan is something like 1% the size of Yellowstone. Yellowstone is 2.2 million acres and it has 66 ecosystems. Mannahatta had 55.

It’s an interesting thought exercise to imagine what might have happened had the United States been colonized from the West instead of from the East. We might have decided to make Manhattan a national park. We would be coming to New York for an entirely different sort of wildlife.

Kimmelman: The Dutch and English, of course, saw the island as a commercial paradise.

Sanderson: It had vast forests of timber. There were otter, beavers, mink, oysters, brook trout, bears. We have historical records of a black bear being shot in the vicinity of Maiden Lane during the 1630s. We know wolves lived on Manhattan until the 1720s.

The Dutch left behind these almost overwrought descriptions of how beautiful and abundant the landscape was — how, sailing here, they could smell the flowers all the way out into the ocean.

Kimmelman: And they saw?

Sanderson: Sailing into the harbor they saw what the Lenape called Pagganck, or Nut Island. Today we call it Governors Island. Back then, it was covered with walnut trees, hickory, chestnuts. And from the ocean they could already see Todt Hill on Aquehonga Manacknong, which was the Algonquin name for Staten Island.

That’s really hard to say. Forgive me. I’m not a linguist.

Kimmelman: No problem.

Sanderson: Todt Hill is the highest point on the entire Atlantic coastal plain between Cape Cod and Florida.

Kimmelman: Todt means dead.

Sanderson: The hill was barren. It was barren because that spot on Staten Island is an old bit of scraped-up sea floor, made of serpentine rock, which has high levels of magnesium but not much calcium, meaning it’s not so good for trees.

Kimmelman: Was all of Staten Island scraped up from the sea floor?

Sanderson: Oh no. The west side of Staten Island belonged to what is the Palisades rock formation. And the east side — the area that flooded during Hurricane Sandy — is on the coastal plain, which was mostly salt marsh.

Kimmelman: So the island is a geological patchwork.

Sanderson: From hugely different ages, too. The rocks, which underlie much of Brooklyn and Queens, not to mention most of New England, are about 540 million years old. The Palisades derive from volcanic basalts formed during the Triassic and Jurassic eras, the time of the dinosaurs.

Kimmelman: Meaning 250 to 150 million years ago.

Sanderson: Right. And if we drilled down where we’re standing now, we would find Manhattan schist, which is even older — pre-Cambrian.

Kimmelman: Eric, we’re hurtling toward the Big Bang. Could you briefly explain how Mannahatta got to 1609? Before colonists brought disease and drove the Lenape from their land?

Sanderson: It’s a long history, obviously. The center of the North American continent is called the North American Craton, which includes some of the oldest rocks on Earth. New York City was on the edge of the craton — imagine Japan with respect to Asia. It was part of a series of islands we call Avalonia.

Over time Avalonia slammed into the craton, geologically speaking. The east side of the East River is pretty much the edge of the old continent. Most of Queens and Brooklyn are what used to be Avalonia.

Kimmelman: Translation for older New Yorkers: Katz’s deli on Houston Street was the craton, Junior’s on Flatbush Avenue was Avalonia.

Sanderson: More or less. Then there’s an extensive glacial history — at least seven glaciation events over the last 620,000 years. The glacial event that matters most peaked about 21,000 years ago. It was called the Wisconsin glaciation. The glacier stopped in Brooklyn and Queens, giving us what are now Brooklyn Heights and the hills of Bay Ridge, Prospect Heights, Crown Heights.

Kimmelman: If the Wisconsin glaciation buried Manhattan, how much ice would we have been standing under here?

Sanderson: How tall are these skyscrapers?

Kimmelman: Well, 1 State Street Plaza, facing the ferry terminal, is 42 stories, about 450 feet high.

Sanderson: The ice was more than three times that thick.

Kimmelman: So we’re talking the Empire State Building.

Sanderson: Then as the climate changed, the glacier retreated and a whole series of giant glacial lakes formed. We would have been at the bottom of Lake Albany, which extended all the way up to New York’s state capital. About 13,500 years ago the lakes gave way in a cascade that brought billions and billions of cubic feet of water roaring down from upstate, breaking through the dam that had separated Lake Albany from the coastal plain and forming the Verrazzano Narrows.

Kimmelman: And that’s when we got the harbor and the topography we now know?

Sanderson: There were lots of steps in between. But by about 5,000 years ago, we had the oak and hickory forests that Henry Hudson would have seen when he arrived. He would have seen another island, too, Kioshk, as the Lenape called it — we call it Ellis Island, which was called Gibbet Island during the 1700s because the English hanged pirates and criminals there.

It became known as one of the oyster islands because geological events had turned the harbor into an ideal home for oysters and a superhighway for the sort of fish that swim from saltwater upstream to breed in freshwater, like shad or sturgeon. We know from historical records that people caught hundreds and hundreds of fish in a few hours just casting their nets off Ellis Island during the 18th and 19th centuries — before the harbor became polluted and dams were built that closed off streams upriver where the fish had gone to breed.

Kimmelman: You mean, until we screwed everything up.

Sanderson: No. No. Well, yes. The point of the last 22 years of my life is not to make people feel bad or to say that we should just wipe out the city and restore it all back to forest. I love New York. Every species has its way of being. Our human way of being is that we talk to each other; we can share ideas about the past so that together we can plan a future that includes nature.

Kimmelman: You’re not from New York.

Sanderson: No, I grew up in the Bay Area. A biology teacher in high school led trips along the John Muir Trail in the Sierra Nevada, from Yosemite to Mount Whitney — 211 miles, 22 days. When I came to New York City, I was reminded of what I loved about the trail — all these layers of complexity, these tall peaks and deep valleys, abundant life in a dramatic landscape. Just a different kind of life.

I moved here in 1998, and one day I went to the Strand bookstore and was flipping through books on New York and saw “Manhattan in Maps” by Paul Cohen and Robert Augustyn, two map dealers. They had taken a photograph of the British Headquarters Map.

Kimmelman: Which British cartographers drew up in the early 1780s.

Sanderson: I realized that if I could geolocate that map and fit it to Manhattan today, I could figure out what was here centuries ago.

Kimmelman: Which is sort of what we’re doing. By the way, where we are standing, was this the shoreline in 1609, or is it landfill?

Sanderson: We’re around the rocky edge of the shore. What’s now Pearl Street marks the approximate shoreline on the East River side. The Dutch and the English wanted to expand the island into the rivers, not move uptown, so they sold water lots to people who were then under contract to fill the lots in. They would knock down hills and use that soil or take garbage from the dump. What’s now the land between Water Street and the FDR Drive is all landfill, like much of the west side, which in 1609 was a white sand beach all the way up to 42nd Street.

Kimmelman: Let’s start walking?

Sanderson: If we were to head uptown, Broad Street takes us to the steps of Federal Hall, across from what’s now the New York Stock Exchange on Wall Street. Broad Street used to be a valley with a salt marsh. Wall Street marks the edge of the forest. It’s called Wall Street because the Dutch built a defensive wall out of wood. The forest was hickory, chestnut, oak, sycamore. Sycamores are also called buttonwoods because they’re good for making buttons. The Buttonwood Agreement, which legalized the trading of securities, was supposedly signed under a sycamore outside what’s now the Stock Exchange.

From there north, around where Nassau Street reaches Fulton Street, there were tulip trees, 100 or 150 feet high.

Kimmelman: The skyscrapers of the 1600s.

Sanderson: With soft, very straight trunks, which is why the Lenape dug giant canoes out of them. Then, where Broadway approaches what’s now City Hall Park, the forest probably opened up onto fields, where we think the Lenape may have tended corn, beans and squash — Three Sisters gardens, they’re called. The land was relatively flat with the right soils. And it was south of what was called the Collect Pond. We think a community of Lenape probably lived just north of City Hall Park on an inlet of the pond where the New York State Supreme Court building is now.

Kimmelman: How big a community?

Sanderson: Maybe 15 people. Maybe 100. No one knows for sure. You have to imagine this was a community that, before the Dutch and English came, would have pretty much spent their entire lives with each other, encountering maybe the occasional trader from northern Manhattan or Brooklyn, or farther afield, like New Jersey.

Kimmelman: In your book it’s clear that the history of Manhattan is in many ways the story of the Collect Pond. Where was it?

Sanderson: Well, where the Javits building is today was roughly the west edge of the pond; that was a hill named Kalck Hoek by the Dutch because of the mounds of oyster shells the Lenape had left on it. Kalck means “chalk” or “lime,” from the shells. To the north of the Collect Pond, Bayard’s Mount was the tallest hill around, from the top of which you could see to the Verrazzano Narrows.

Imagine the Collect Pond sitting within this amphitheater of hills, protected from the winter winds. The water was fresh, very deep — maybe 80 feet deep — fed by springs. An outlet stream flowed north from the pond to the Hudson River, along what’s now Canal Street. Another stream, Wolfert’s Brook, flowed southeast to the East River, along Pearl Street, past 1 Police Plaza.

Kimmelman: Continuing the old-school restaurant theme: south of Chinatown’s Nom Wah Tea Parlor and the Great NY Noodletown.

Sanderson: Right. The Collect Pond was the freshwater source for early New York. In the American period, commercial businesses started to settle along the shore of the pond, and by the late 18th century it was becoming polluted. As the city grew, tanneries, which were essential but stank and used toxic chemicals, kept getting pushed farther north because no one wanted to live near a tannery. They ended up at the pond, dumping their waste in it.

Kimmelman: The city poisoned its own water supply.

Sanderson: It’s an interesting parable about unintended consequences. When the pond became a cesspool, the city decided to fill it in by leveling Kalck Hoek and Bayard’s Mount. But the landfill was so badly done that the buildings they built on it sank into the mire. That’s when the neighborhood became notorious as Five Points, which Charles Dickens described as the worst slum he had ever seen. And he knew his slums. The city finally cleared the area and created the neighborhood we more or less now know, with the courthouses and municipal buildings.

Kimmelman: For want of a nail, in other words?

Sanderson: The ripple effects were even more dramatic. Because the city polluted its own water supply, lower Manhattan needed to find another water source, which led Aaron Burr to form the Manhattan Company. The company charter included a provision that allowed Burr to use most of the assets for something besides water. So he formed a bank, which today is JPMorgan Chase.

Kimmelman: Which was Burr’s real ambition. He, I think, argued for the water company after the city suffered an outbreak of yellow fever. Then the company built a system so poor it provoked a series of cholera epidemics.

Sanderson: Which in turn led to the construction of the Croton Aqueduct, a remarkable engineering feat to bring water by gravity 41 miles south to reservoirs in the city, which in turn had its own ripple effects on the rest of the island. Why do we have the flat Great Lawn in Central Park? Because that was originally the site of a receiving reservoir called Lake Manahatta. Why is the Public Library at 42nd Street and Fifth Avenue? Because it replaced another massive reservoir on Murray Hill.

Kimmelman: Edgar Allan Poe described the views from the top of the 42nd Street reservoir, where he said he could see “the whole city to the Battery, and a large portion of the harbor.” Then, of course, we got the library building by Carrère & Hastings.

Sanderson: All traceable to the Collect Pond. I have this friendly bet with an urban geographer whose theory of cities is that they only change through crises — like the one we’re experiencing right now. There’s certainly the historical case for that.

But, knowing our history, we also have the capacity to make better decisions, to do the right thing.

Kimmelman: That doesn’t mean we will.

Sanderson: We can hope.

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