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Anna Espinola

"Sometimes you feel like you're not in the city anymore," said urban ecologist Jason Munshi-South as we stood at the edge of his Highbridge Park field site in Washington Heights. It was an unusually idyllic August morning in Manhattan—warm but not humid, with the sun glinting off sycamore leaves in the park below us.

A professor at Fordham, Munshi-South studies small mammals in New York City and its surrounding suburbs. That morning, I met him and his graduate students at the corner of Edgecombe Avenue and 167th Street to pick up the 100 small mammal traps they had put out the evening before. The traps were baited with birdseed and designed to close behind the animal—in Munshi-South's hopes, a white-footed mouse (Peromyscus leucopus)—so that blood, tissue, and other kinds of biological samples could be taken back to the lab for analysis.

Munshi-South is one of countless urban ecologists working to determine how New York City's highly urbanized infrastructure affects its lesser-known inhabitants, from plant communities on green roofs to plankton living in the Hudson and East rivers.

In Munshi-South's case, the star subjects are small mammals and amphibians, namely the white-footed mouse, native to the New York region; the infamous brown rat, Rattus norvegicus, originally from Norway but better known for the home it has made for itself in the New York City subway; and the northern dusky salamander, Desmognathus fuscus, whose population in New York has drastically decreased in the face of habitat fragmentation and reduced water quality.

Through genetic and demographic studies of these focal species, Munshi-South hopes to learn whether the process of urbanization in New York City and its effects on local "wildlife" are comparable to the effects of urbanization in other cities around the world.

That is, are the changes that Munshi-South observes in white-footed mouse genes unique to New York? Or, as he phrases it, "Is there a 'syndrome' such that species evolve in the same ways in different cities at the same latitudes?"

New York City is an unexpectedly fascinating field site for Munshi-South and other ecologists. We may think of New York as a concrete jungle on a day-to-day basis, but the truth is that New York can be seen as a complex, ever-evolving ecosystem brimming with biodiversity. We don't live in a city; we live in a habitat. It's all just a matter of perspective.

Urban Ecology Defined

According to the World Health Organization, 54 percent of the total global population currently lives in urban areas, and that number is steadily increasing. It's no wonder the effects of urbanization on plant and animal life are becoming increasingly prevalent in not only the scientific literature, but in everyday life as well.

Compared to its parent field of ecology—which has roots as far back as the ancient Greeks—urban ecology is a relatively young field. Only in the 1970s did a few brave visionaries begin applying concepts from traditional ecological theory to urban landscapes, asking such interdisciplinary questions as: What differentiates an "urban" place from a "nonurban place"? How are green spaces in cities different from green spaces outside of cities? How can we optimize patterns of consumption to reduce environmental degradation?    

Why urban ecology took so long to develop as a formalized discipline is perhaps a matter of semantics—many see "nature" as impossible to study in an urban environment. Michael Levandowsky, who completed graduate degrees at Columbia in the late 1960s and who has done work on marine phytoplankton in the Hudson River estuary, recalls that "back in the '80s, I had been going to the equator and to the eastern Canadian Arctic and sampling, but people would ask me about the Hudson River and the East River. … And I didn't have a clue, even though they're both within walking distance of my lab."

Thus, Levandowsky is now working alongside scientists at the American Museum of Natural History to conduct genetic analyses on protistan plankton communities in those very waters.

Since the '80s, an expanding community of ecologists, biologists, and engineers has taken on the vast amount of ecological work left to be done in urban areas like our own. At Columbia and Barnard, several faculty members or one-time affiliates are currently working on ecological projects within New York City. The city is, after all, an ideal field site for students: local, affordable, and relatively under-studied.

Rebecca Calisi, a new biology professor at Barnard, hopes to study the effects of urbanization on the pigeons for which New York City is notorious. Matt Palmer, director of undergraduate studies for the ecology, evolution, and environmental biology department, has partnered with Barnard biology professor Krista McGuire on a citywide study of green roofs. Palmer and Timon McPhearson, assistant professor of ecology at the New School and former Columbia science fellow, are currently studying the efficacy of the city's MillionTrees initiative, which aims to plant one million trees in New York City by 2017.

Still, the perception of New York City as incongruous with nature seems hard to shake. Myla Aronson, a plant ecologist at Rutgers University who studies invasive species and biodiversity in the New York metropolitan area, explains that people "think of [cities] as concrete jungles, but they're actually surprisingly diverse."

In her most recent work, Aronson collaborated with urban ecologists all over the world to assess whether cities lack biodiversity. The answer was clear. "We found that 20 percent of the world's birds are found in only 54 cities. … And 5 percent of plant species were found in these cities, but there's a lot more plant species than there are bird species."

To provide some perspective on those statistics, in the mid-2000s, Columbia's Socioeconomic Data and Applications Center estimated that only 2.7 percent of land surface in the world was classified as urban development—and geographers took issue with that number as an overestimation. In other words, Aronson's work supports the idea that an unexpectedly substantial proportion of the world's biodiversity can be found in cities.

Helen Forgione, senior project manager for the Natural Areas Conservancy, agrees that urban nature is still under-acknowledged by the public. "I think it depends a lot on who you're interacting with. In my New York City science and ecology bubble, everybody has a really good understanding of how rich the natural areas are within New York City and how unique they are," she says. "But, for instance, when I talk with family members or friends in New York City, everyone always says, 'Oh yeah, Central Park!' They don't know that there is so much out there, and the diversity of it, and the importance and the vitality of these natural places in the city."

What differentiates an “urban” place from a “nonurban place”? How are green spaces in cities different from green spaces outside of cities? How can we optimize patterns of consumption to reduce environmental degradation?

Natural Incentives

Of the 30,000 acres of land managed by the New York City Parks Department, 10,000 can be considered "natural areas." As Forgione defines them, natural areas consist of "forests, freshwater wetlands, salt marshes, and grasslands where predominantly ecological processes are what maintain the status of the area," as opposed to landscaping or gardening. And as important and vital as we know these landscapes to be—for storm and climate change resilience, health benefits, and recreational enjoyment by New Yorkers—scientists believe they are still underutilized.  

For example, McGuire's work on the microbial communities of green roofs is primarily guided by her interest in green roofs as novel ecological communities. They are, she explains, "kind of like a 'Mars habitat': They're really dry, they're exposed to high UV, high winds." However, her project is also framed by the idea that microbes can provide enormously valuable—and still untapped—services to the ecosystem.

"We're trying to do interdisciplinary work with engineers, with climate scientists, with social scientists and biologists, to try and figure out how we can optimize green infrastructure," McGuire says.

For McGuire, green infrastructure can be found in unlikely places. The Barnard professor is most interested in green spaces surrounding New York City's combined sewer overflow system, an outdated but still-popular sewer system that is used in large cities all over America.

As was described to me by several of the scientists I interviewed, the CSO system in New York City works like this: On flushing the toilet, raw sewage is shuttled along an underground piping system to one of 14 water treatment plants throughout the five boroughs. There, the water is treated so that it is clean enough to be released into the waterways surrounding the New York City metropolitan area. However, if there's a sufficiently strong precipitation event (in some areas, only an inch of precipitation qualifies as sufficiently strong), the water level in the sewer system rises, causing raw sewage to mix with stormwater. This muck flows out from 494 permitted outfalls in the city—directly into the Harlem, Bronx, Hudson, and East rivers, among other waterways. Obviously, this is an unfortunate situation, and it's one that McGuire thinks microbes could help fix.

"It's actually cheaper to build green infrastructure to deal with the problem than to redo the piping system," which would be prohibitively expensive, she says. "What the green infrastructure does is it captures the precipitation, and the water then is taken up by the plants and recycled back into the atmosphere through transpiration. If you can decrease the amount of precipitation that goes into the stormwater overflow system, then you can actually minimize how much raw sewage mixed with stormwater is deposited into the waterways."

However, all microbial communities are not created equal. McGuire's current mission is to find the combination of microbes that would best mitigate the problems of the city's CSO by maximizing the amount of precipitation captured.

In a related project, McGuire hopes to work out whether a specific microbial community might enable green roofs to most efficiently self-sustain, so that fertilizers need not be added to the system after the initial creation of the roof.

"If you have a microbial community that's really efficient at decomposing in the specific climatic conditions—the harsh conditions of a green roof—can we make that a self-sustaining system so that we don't need to put phosphorus and nitrogenous fertilizers in?" When you put fertilizers in and it rains too much, she explains, "then you're defeating the purpose because you're actually adding nutrient loading to the stormwater that we're trying to minimize."

McPhearson is also in search of the optimal species to enhance the city ecosystem's resilience. Already made harsh by heavy metal contamination, New York's soil is likely to become even more inhospitable to trees as the effects of climate change continue to manifest. But we need trees—having a "closed canopy" is key for carbon and water storage, as well as urban cooling. Without urban cooling, the city runs a greater risk of becoming an urban heat island—a phenomenon in which a high concentration of buildings causes city temperatures to be higher on average than those of nearby rural areas (widely studied by Columbia's own Stuart Gaffin)—perhaps the reason why the city feels so unbearably hot in the summer.

McPhearson and Palmer co-lead the ecological study associated with the MillionTrees project. The $400 million initiative is funded by PlaNYC (New York's "sustainability and resiliency blueprint") and the New York Restoration Project. "We're trying to understand which species will make it, which species won't, which ones are most adapted to different kinds of conditions," McPhearson says. With this knowledge, McPhearson hopes to advise members of the Parks Department who are actively planting trees throughout the city.

"One of the things we've found is that the soils are highly variable around New York City," he says. "The history of the place turns out to matter a lot for the ecology … the history of the development of a particular park, especially where the soils came from, matters a lot for how the plants and trees are responding to planting."

Overall, McPhearson says young oaks can tolerate high heat, soil compaction, and other factors that can normally cause stress for young tree seedlings.

But, as in any compelling study, the answers McPhearson has found thus far have only provoked more questions. For example, "What about climate change impacts both on young and older trees?" The oaks, he laments, may be good in the establishment phase, but "large trees that have huge canopies that are providing all these benefits are more susceptible to high winds than the young ones because they catch and hold the wind like a sail."

All of these considerations tie into one overarching theme of the conversation I had with McPhearson: The interface between design and ecology has never had so much potential as it does in the context of urban ecology research happening right now in New York City.

"It makes it complicated to think long-term and, to me, it showcases the importance of long-term planning in the design process," he says. "It's not just true for a building withstanding a storm surge, but also true for trees withstanding other effects of climate change."

Green Equity?

Beyond the MillionTrees project, McPhearson sees the opportunity to integrate design and ecology in much of his own work regarding vacant lots. As noted in one of McPhearson's research articles, "In NYC, the Department of Finance defines a vacant lot as a parcel of land 'on which no lawful structure exists and which is not otherwise being used for any purpose for which it may lawfully be used.'" While some vacant lots are quickly absorbed for community use—parks and gardens for example—McPhearson has found that not all vacant lots fulfill their potential to benefit their residents.

"It's hard to find a new place to put in some green infrastructure that can help meet some of these objectives for health, or objectives for resilience to climate change, or objectives for ecosystem services," McPhearson says. "But vacant lots provide an opportunity because … they're this way of providing better access to green space for people that have the highest need, which would be low-income minorities."  

McPhearson's work on vacant lots speaks to the often-interdisciplinary nature of ecological work conducted in New York. Because human influence on areas under study here is unavoidable, more scientists seem to be thinking about the socioeconomic implications of improving green spaces in cities than ecologists working in traditional, nonurban settings.

Indeed, Forgione notes that the Natural Areas Conservancy identifies social justice as one of its explicit goals: "The Natural Areas Conservancy exists to restore and conserve green and blue spaces of New York City in order to enhance the lives of all New Yorkers." And while she is managing the ecological side of the Natural Area Conservancy's assessment of natural areas, a team from the U.S. Forest Service is simultaneously conducting a more social assessment of natural areas and parks, looking into who uses them most and least.

Working out of the Urban Field Station in Fort Totten, Queens, the social assessment team is asking questions about how people use green spaces in New York and how best to integrate that information with knowledge about the health of natural areas emerging from the ecological study.

"One thing about our mission for Natural Areas Conservancy is that it's not as focused on a single park or a single neighborhood or a single constituency," Forgione says. "There's one of these natural areas accessible to just about any neighborhood and certainly any borough, so that that speaks to an equity. We want to improve these places and conserve and preserve for all the New Yorkers that are near them."

Beyond increasing infrastructural resiliency, expanding green spaces—even on very small scales—is known to have health benefits. "When looking out your window, you see a park, or you can even see a single tree, or a little patch of green—even that can provide stress relief and mental health benefits," McPhearson says.

And while the extent of these benefits is unknown, more health professionals and ecologists are attempting to quantify the reduction in health care costs that may be possible through green initiatives. "My hunch is that when we slowly work out the value of urban ecosystems to health, the actual monetary value of that will be enormous," McPhearson says. According to the United Nations Department of Economic and Social Affairs, over 80 percent of Americans live in urban areas. Given this, "the potential to influence human health through urban greening, or other kinds of ways to make cities greener and more livable, is vast, and we're potentially talking about many billions of dollars," he adds.

The ability of even small-scale greening ventures to improve the lives of many is one of the attributes that draws McPhearson to vacant lots. "They tend to occur in areas where people have low income and are minorities, places where also, if you map these out, are hot spots of various health issues, whether it's asthma or obesity or whatever it happens to be."

Likewise, Aronson—the plant ecologist at Rutgers—feels there are ethical reasons for conserving urban nature, particularly native biodiversity.   

"There's this perception that cities are homogenized, or all the same, all across the world—that we share the same flora, that we share the same birds, that we share the same everything. And we really don't," she says. "Cities do maintain the unique biotic heritage of where they are in the world, and that's important."

Future Challenges

New York's hard-working ecologists, engineers, foresters, architects, designers, volunteers, and public servants make it look easy, but negotiating ecological change in our fair city is not without its challenges.

Perhaps first and foremost among these obstacles is inertia in public opinion. Despite 30-odd years of study and management, New York continues to be popularly portrayed as devoid of nature. As Forgione pointed out, when people are asked to think of green space in New York, they typically think only of Central Park, bypassing the wealth of natural areas and parks dispersed throughout the city.

This limited awareness is exactly why urban ecologists need the U.S. Forest Service's social assessment, which will be wrapping up in October. An essential next step, says Forgione, will be "understanding how people think about natural areas and how we can more effectively get the information that's needed to New Yorkers so that they can get out there and enjoy these places." He continues, "That's really the future of how these places will persist is by people stewarding these places and understanding more about them."

Citywide ecological knowledge-enhancement initiatives are being aided by public outreach—from science journalism to citizen science projects—that appeal to the New York layman. For example, in 2012, David Maddox, an ecologist and entrepreneur, founded a virtual magazine, the Nature of Cities, which seeks to publicize urban ecological issues related to sustainability and urban nature. Eric Sanderson, a senior conservation ecologist at the New York-based Wildlife Conservation Society, has pioneered a Web application—Manahatta 2409—that allows users to visualize New York City as it was when the first European settlers arrived, as well as what it might look like 200 years from now.

It remains to be seen whether infrastructural and environmental limitations will prove more limiting to urban ecology's potential than public ignorance. While interactions between science and design represent an unprecedented capacity for innovation in the city, such ventures have never been implemented, and they may prove unwieldy in practice. Further, complications of climate change are likely to escalate in ways that make improving the systems we have for resisting storms, dealing with waste, and promoting health even more difficult.

However, these intellectual challenges need not be cause for discouragement. As McPhearson says, "To really understand what's going on in any place, you actually have to know how all these things are working together, which is very challenging, but for me very exciting. I think that's one of the most exciting things we can be trying to figure out, is dealing with the complexity as it exists, and to deal with the complexity without trying to simplify it, and without trying to necessarily compartmentalize it."

The many future projects enumerated by these scientists—from McGuire's aim to discover the urban-adapted microbes with the most efficient decomposing abilities to Aronson's goal of assessing biodiversity in cities all over the world—indicate that while environmental degradation in the city may be grave, there are practical strides we can take, and are taking, to ameliorate it.

One of the first steps is recognizing that New York City may be a jungle, but it is not just made of concrete. Rather, nature can be found in the most unexpected places, if only we learn to look for it.

"Cities aren't designed for biodiversity, they're designed for people. Only recently have we actually started to think about biodiversity and nature in cities, and started to plan for biodiversity," Aronson says. "But what's exciting is that although cities aren't traditionally designed for nature, we're still preserving a lot of nature in them."


urban ecology green roofs environment health wellness urbanization New York City ecology research Climate Change infrastructure