How to Build a Forgotten Landscape from the Ground Up

The science behind the Welikia Hear Welikia pronounced (and Mannahatta) Project is landscape ecology. Landscape ecology is the study of how different ecosystems (e.g. forests, wetlands, streams, etc.) combine together to create habitat for plants and animals. The Wildlife Conservation Society uses landscape ecology to understand how to conserve wildlife and wild places, especially as many of the changes people make to the landscape (e.g. building roads, clearing land for agriculture, constructing cities) affect wildlife species. Our goal in the Welikia Project Hear Welikia pronounced is to build a digital version of New York City’s original ecological landscape, layer by layer, literally “from the ground up,” starting with geology, soils, topography, then streams, springs, ponds, wetlands, etc., eventually working up to species of plants and animals (including people.)

Data from Many Sources

To make this happen, we collected data from many sources. We started with historical maps which described the original features of city. To those we added information from soil surveys, tree rings, descriptions of plant life and animal life, historical accounts, even field surveys from today. For Mannahatta, we “georeferenced” all this information to a single base map, 1782 British Headquarters map from The National Archives in the United Kingdom, and created a geographic information system (GIS) database, in this case, the most complete description of a landscape ever attempted.  For the other boroughs, we will need to use a combination of maps from the 18th and 19th centuries to carefully reconstruct the forgotten landscape.
To recreate Mannahatta, we used GIS software to layer spatial datasets, starting with abiotic layeres like bedrock and soil type and working upward to topography, streams, and eventually species and ecological community types.

To recreate Mannahatta, we used GIS software to layer spatial datasets (i.e. maps), to derive maps of topography, streams, and eventually species and ecological community types, the original ecology of Mannahatta.

Starting from Scratch

The process of layering and analyzing spatial data is not, in and of itself, new. Many different fields use geographic information to answer questions in business, government and science.  The challenge in recreating Mannahatta, or Welikia writ large, is that none of the data layers existed prior to our work. No one alive today knows where the streams flowed in 1609 or where the bears lived or where the oak-hickory forest grew, and the native Lenape people who would have known these things left no maps behind. In other words, we had to start “from scratch.”

Our starting point to reconstruct Mannahatta was geolocating the 18th century British Headquarters Map to the modern street grid of New York.  We found over 200 control points where we could locate features on the map (e.g. streams, hills, ponds) to their current locations.  The final rectification was accomplished with an error of approximately 40 meters, or about half an uptown block in midtown.  Georeferencing the British Headquarters Map with this level of accuracy means that all data layers derived from it will also be that spatially accurate, allowing us to estimate the distribution of ecological features block by block across the city.  The result is a testament to the workmanship of the British military cartographers who created the map.

For the rest of the city, it won’t be so easy, because we won’t have only one map to work with.  Rather we will need to work even harder to synthesize information from many different sources into one composite base map to work with.  Fortunately though because development of the rest of the city (Brooklyn partly excepted) proceeded later in time than Manhattan, we can use maps through most of the 19th century to detect old streams, hills and shorelines that have since been erased by development.

The Digital Elevation Model, or DEM, of 1609 Mannahatta was a vital achievement in the process of recreating Mannahatta. It took 5 years of map research, fieldwork, and GIS analysis to complete. © WCS

The result of five years of historical map research, fieldwork, and GIS analysis, the Digital Elevation Model, or DEM, of 1609 was a vital step in the process of recreating Mannahatta. ©WCS

The Physical Landscape

The complex topography of the “Island of Many Hills” created the basis for over 55 different ecological communities for plants and animals and is an important factor behind Mannahatta’s original biodiversity.

The non-living, physical environment (the soils, waters, hills, and climate) can be thought of as the stage on which the ecological play is acted. Our next objective was to reconstruct these factors; an interesting exercise in itself, especially as these physical factors have been so transformed in the intervening centuries. Mannahatta once had 570+ hills, more than 60 miles of streams, over 20 ponds, and over 300 springs. The rest of the city had many more.  Sandy beaches stretched from the tip of Manhattan to past 42nd Street on the Hudson River shore. And beyond the shore was the vibrant, dynamic tidal estuary, with complex currents, sedimentary pattterns, and the influence of the Hudson River. Together these physical factors made for a stage as interesting as anything on Broadway today.

This image illustrates the differences in the island's elevation between 1609 and today. Grays and blacks indicate increases in elevation, mainly waterways that have been filled in, while browns indicate decreases in elevation, such as leveling hills for construction.©WCS

The Biological Landscape: Ecological Neighborhoods

Over the physical landscape, we mapped the biological landscape of ecological communities. Ecological communities are regularly occurring collections of plants and animals, like forests or wetlands; they can be thought of as “ecological neighborhoods.” Where Manhattan has the Upper West Side and Tribeca today, Mannahatta once had “coastal oak-pine forest” and “red maple swamps.” We used a system of ecological communities for New York State developed by the New York State Natural Heritage Program. Why an ecological community occurs where it does is a matter of the physical conditions of the site plus the interaction of disturbance processes like fire, windthrows, freezing, and habitat change caused by people or other animals (e.g. beavers). Taken together, we estimate the Mannahatta once had 55 different ecological community types. This wealth of different communities in such a narrow space in large part explains the extraordinary biodiversity of the island.  We expect that similar patterns enabled the biodiversity characteristic of the other boroughs as well, with important differences in the different parts of the city.

Mannahatta had 55 different ecological communities, including terrestrial communities (like forests and grasslands), wetland and stream communities, and estuarine communites in the surrounding waters.

Mannahatta had 55 different ecological communities, including terrestrial communities (like forests and grasslands), wetland, pond and stream communities, and estuarine communities in the surrounding waters.©WCS

Mannahatta’s Abundant Wildlife

If the physical landscape sets the stage, and the ecological communities are the setting in which the play is acted, the ecological actors are the species. Through a long process of compiling historical and modern sources and consulting with scientists from many disciplines, we developed a species list for Manhattan. We can not be certain of exactly what species were once on the island, so we describe different species by their probability of occurance: likely, probable, possible and remotely possible. In total, our research leads us to conclude that just over 1000 species of plants and vertebrate animals (24 species of mammals, 233 birds, 32 reptiles and amphibians, 85 fish, and 627 species of plants, and unknown numbers of fungi, lichens, mosses, insects, shellfish and other invertebrates) once occurred on Mannahatta. These likely wildlife included wolves, black bears, mountain lions, beavers, passenger pigeons, heath hens, timber rattlesnakes, tree frogs, bog turtles and over 30 species of orchids and 70 species of trees.
We expect but don’t know yet that the biological abundance of Welikia Bronx, Queens, Brooklyn and Staten Island will be greater than Manhattan’s.  We use similar techniques as for Mannahatta, but tailor them to these other four boroughs, producing borough specific species lists for the entire city.
The beaver, an ecological architect and disturber. Julie Larsen Maher ©WCS

Mannahatta was home to a large population of beavers. These "ecosystem architects" build dams to create beaver ponds -- a unique ecological feature that would not otherwise exist. This particular beaver is named Jose; he re-colonized New York City in 2008 after a near 200 year absence of his kind from the city. Photo by Julie Larsen Maher ©WCS.

The Lenape – The Original New Yorkers

The abundance of wildlife, the island’s location near the estuarine waters, and the hilly topography made “Welikia” Hear Welikia pronounced a great home for the Native American Lenape people, who lived on the island when Hudson arrived.  The Lenape and their ancestors lived in this area for thousands years before European contact, obtaining all the food, water and materials they needed from the surrounding forests, wetlands and waters.  In Northeast Algonquin culture, the Lenape were considered the “Ancient Ones;” they told legends of North America as “Turtle Island;” and their folklore suggests a close connection to the land and appreciation of their role, one among many, given the plentiful other species which shared the landscape with them.

We studied the effect of the Lenape on the landscape through computer models, based on the reconstructions described above.  We used a wildfire model created by the U.S. Forest Service to estimate the effect of Native American fire on the landscape, showing that through repeated burning as little as once every 10 years, places like the Harlem Plains could be transformed from forest to grasslands.  We also created a geographic model of shifting horticulture and estimated how much crops like corn, beans and squash (the traditional “three sisters” garden) contributed to their diet.  Today after a long diaspora, Lenape people live in Oklahoma, Kansas, Wisconsin, New Jersey and Ontario, Canada.

Chief Tishcohan, the late Delaware chief. Courtesy of The Historical Society of Pennsylvania Collection, Atwater Kent Museum of Philadelphia.

The 1735 portrait of Lenape Chief Tishcohan by Gustavus Hesselius. Courtesy of The Historical Society of Pennsylvania Collection, Atwater Kent Museum of Philadelphia.

Muir Webs

Once we had the species lists, an understanding of the physical and biological landscapes, and a sense of how Native Americans affected the ecology of the island, we wanted to know where different species lived on Mannahatta. In scientific terms, we wanted to map the habitats for all the species.  This led to the invention of a new way of understanding and visualizing ecosystem relationships called the Muir Web.

Habitat is defined as the place where an plant or an animal can be meet its basic ecological needs, that is, needs for food, water, shelter, and reproductive resources (e.g. materials for building nests, or a den where an animal can give birth). We began compiling habitat descriptions for the 1001 likely species of Mannahatta into a database, using habitat information found in field guides. A tree species might grow best in “dry sandy soils” or a warbler may eat “tree insects, especially in open deciduous woods.” As we developed these lists, we added entries to include the definition of “openness” or of “woods” and eventually even “dry sandy soils.” We reconstructed the habitat relationships until eventually they reached the physical and ecological variables we had mapped, and then even further. At the base of the “Muir Web” of habitat relationships are fundamentals like space, time, geology and climate. We named these webs of habitat relationships (inclusive of food webs, but adding additional relationships) after John Muir, the famous naturalist. John Muir once wrote “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.” The Muir Web for Mannahatta makes these cords visible for all to see.

This Muir Web shows all the habitat relationships for all the species on Mannahatta.

This Muir Web shows all the habitat relationships for all the species on Mannahatta. Visualization by Chris Harrison of Carnegie-Mellon University. ©WCS

To learn more about Muir webs, watch a presentation made at Columbia University on September 18, 2009.  For Welikia Hear Welikia pronounced we will create a Muir web separately for each borough of city, reflecting the differences in species and ecological community composition.  Also based on a study conducted in 2009-2010 by Dr. Eric Sanderson and Dr. John Waldman (Queens College), we believe we now have a way of incorporating seasonality into the Muir webs, and thus express different data views of the pre-European natural landscape in different seasons.

Cities as Habitat

Thinking of Welikia’s Muir webs can lead one to wonder: what are the webs that sustain us today?  In New York City we can trace connections to our friends and family, to our workplaces, to public institutions like the police and the fire department, and to our causes, whether we support music, arts or nature conservation.  Just as Mannahatta nurtured so many plants and animals, so Manhattan today nurtures so many kinds of people.  Diversity, density and interdependence are still alive and well on Manhattan, though the players have changed; and surprisingly, more of nature persists in New York that one might think.  An important part of the Mannahatta Project is not leaving ecology in the past, but to appreciate it in our current times, to see how we can live in ways that are compatible with wildlife and wild places and that will sustain people and planet Earth for the next 400 years.

Through the Welikia Project Hear Welikia pronounced we aim to quantify the changes to the landscape that have happened over the last 400 years, so that we can help the city create a plan to re-invigorate the nature of the city over the next 400 years.  Our plan is to compare our historical species lists and ecological community maps to existing information about the biodiversity and ecosystem composition of the city today.  Some species will still be here (perhaps some even in greater abundance, like the peregrine falcon); others may be entirely and irretrievably gone (like wolves or black bears); while others perhaps could come back through conservation efforts.  We wish to push the boundaries of what is possible for the future by looking to the past, and therefore contribute to New York City’s greatness, not only for its people, but for all of nature.

To learn more about the science of Mannahatta, read Eric Sanderson’s Mannahatta: A Natural History of New York City (Abrams, 2009).

To find out more about Welikia, become a “Landscape Ecology Insider” by supporting one or more boroughs through the Welikia Map.  Click on any borough to begin.  For Manhattan you can support any block to gain insider access to our work.