Urban Ecology

One Saturday morning last fall, a group of New Haven teenagers took to the streets in the face of one of the city’s grimmer urban perils—Yale and Harvard football fans in cars and on foot pressing resolutely toward the Yale Bowl for The Game. The timing was bad. The teenagers were moving young trees into position for planting, with the help of a hand truck. Some of the trees were 20 feet long and weighed 300 pounds, and the drivers were in a hurry. “They didn’t give us much room to cross,” Terrance Walker, a junior at Common Ground High School, recalled recently. But it was late in the season and the group needed to get 17 trees into the ground. It was, ironically, a traffic-calming experiment, built on the hypothesis that trees can change behavior.

Neighbors on Edgewood Way had complained about speeding, and, at least in theory, narrower sightlines from a corridor of trees would slow traffic. If that didn’t work, a city official suggested, the trees would at least dampen the sound of car engines—and look good doing it. Speed bumps or other engineered remedies would have cost anywhere from $15,000 to $250,000, he said, versus $4,000 for the trees. Common Ground students will track the results for four years to see if it works, using speed data from the city.

The Edgewood Way planting was an experiment in other ways, too. A few years ago, city officials noticed that F&ES’ Urban Resources Initiative (URI) was getting trees into the ground for less than the city paid to have professional landscapers do the job—and with a 92 percent survival rate versus a 60 percent national average for professionals. A key difference was that URI’s Community Greenspace program typically found neighborhood stewards for the new trees, often among the volunteers who had planted them. Instead of being threatened by that success, city officials decided to capitalize on it by turning New Haven’s entire tree-planting program over to URI, with the city paying for the trees and URI providing the labor.

“When the city asked us to be the sole source of planting,” says URI director Colleen Murphy-Dunning, “our board said, ‘Let’s use this as a way to engage teens,’” a segment of the city population that Community Greenspace had generally failed to reach. The result was a new program called GreenSkills, which hires and trains teenagers to plant trees as an early step into the job market. It worked out so well that this year the city is roughly tripling the challenge to URI.

“Our partnership with URI is gold,” says Bob Levine, New Haven’s director of Parks, Recreation and Trees. “They’re so focused on planting trees, they do it so well and they communicate so well with the people in the neighborhoods and the aldermen—they do absolutely everything. And after four or five years, not to have any complaints—any complaints—and to have people say they’re happy, it’s just gravy for us.”

The partnership also turned up a major weakness in the city’s tree program. Until 2007, New Haven had been planting about 200 street trees a year. But maintenance crews were also removing 500 dead, diseased or dangerous trees each year. That gap became the focus of attention at a meeting last summer where URI was presenting a satellite study of New Haven’s tree canopy, prepared with the U.S. Forest Service and the University of Vermont. The declining state of the city’s tree canopy caught the attention of Mayor John DeStefano Jr. So did the disparities in tree cover in different neighborhoods, from 64 percent in West Rock down to 23 percent in the Hill and 6 percent in Long Wharf. In October, DeStefano announced a program to add 10,000 new trees over the next five years, with half to be planted on private property by companies, universities and other organizations—and half to be planted by URI.

Thus GreenSkills will hire and train 50 teenagers this year, with the first crew planting 300 trees during the spring season alone. Another new URI program, modeled on a similar effort in New York City, will employ people re-entering the community after being released from prison. And residents of the Crossroads substance abuse program, who have worked as Community Greenspace volunteers in the past, will now also become paid workers. The aim isn’t just to plant 1,000 trees, this year’s goal for URI, up from 350 last year, or to reverse the decline in New Haven’s tree cover, says Murphy-Dunning, but also to build communities economically, socially, environmentally, even spiritually. And in that sense, what’s happening on Edgewood Way is part of a much larger global experiment in urban ecology—a new way of looking at cities and people that owes much of its rising popularity to work originally done at Yale.

An Urban Species

A few years ago, for the first time in our history as a species, Homo sapiens became a predominantly urban species, as people worldwide shook off the dust of rural life and moved to town. We crossed the halfway mark sometime in 2007 or 2008, according to a United Nations estimate, en route from being about 30 percent urban in 1950 to 60 percent urban by 2030. The trend is even more advanced in the United States. About 80 percent of Americans now live in urban areas, which also sprawl across a rapidly expanding share of the American landscape. In less than a lifetime, from 1990 to 2050, the U.S. Forest Service estimates that urban land area will more than triple, from 2.5 percent to 8.1 percent of the lower 48 states. In Connecticut and three other Northeastern states, the land will be more than 60 percent urban by mid-century, up from about 35 percent now.   

So what does it mean to become a city-dwelling species? And how should it change the way we think about the forest in the city?

Until recently, even scientists did not pay much attention to this epochal shift in the way people live. “When I was an undergraduate, if you wanted to do urban ecology and examine the design of cities and the relationship between people and the environment, it was a path to obscurity,” says Morgan Grove, Ph.D. ’96. “It was considered trivial and unimportant. That’s not what ecologists did.” Places with lots of people were the antithesis of nature, an attitude dating back at least to Thomas Jefferson, who once described great cities as “pestilential to the morals, the health and the liberties of man.” Outside the scientific world, planting street trees in cities tended to be little more than an Arbor Day photo opportunity for local politicians and an afterthought in urban budgets. 

But that attitude has changed dramatically over the past few years. City planners and politicians have begun to see trees and “green infrastructure” as a practical alternative to costly technological fixes—not just for traffic calming, but also for controlling air and water pollution, reducing energy demand and urban heat-island effects, preventing floods and adapting to climate change. Likewise, psychologists and social scientists have begun to pay attention to new evidence that trees can make people feel better about where they live, reducing stress, lowering crime rates, improving educational outcomes and helping to minimize asthma hospitalizations and heat-wave deaths. Even ecologists, who once could not see the urban forest for the buildings, have come around. Their recent research suggests that cities are more important to biodiversity than previously thought—and with a little planning could become much more so even as urban areas expand.

The idea that trees can build better cities has recently helped launch “million-tree” initiatives in Los Angeles, New York, Salt Lake City, Indianapolis, Denver, Houston and other cities, generally with a timetable of planting that many new trees within five or 10 years. Corporations and other organizations not normally associated with environmental causes have also signed on to the movement, with the American Bar Association, for instance, committing to planting a million trees by 2015. Even some supporters worry that the current zeal for urban tree planting may be too much, too fast, particularly where the planters neglect to provide for the unglamorous work of maintaining the trees. Such campaigns have sometimes produced little more than favorable publicity in the past. But the new initiatives now often come with highly specific and far-reaching purposes in mind. 

For instance, planting trees might seem at first like an improbable tool for dealing with combined sewer overflows (CSOs)—a common problem in older cities where domestic wastes and stormwater run through the same pipes. Many cities now face federal deadlines—and huge construction costs—to stop such systems from spilling raw sewage into basements and waterways during rainstorms. The conventional engineered, or “gray,” remedy is to build massive deep tunnels capable of retaining overflow, to be released gradually through municipal water treatment plants after the rain stops falling. But cities are now also pushing to prevent the water from getting into the system in the first place by using trees, green roofs and permeable pavements to sponge it up where rain falls. 

In one typical case, the Milwaukee Metropolitan Sewerage District has spent $4 billion over the past two decades on gray remedies, adding 494 million gallons of deep-tunnel storage. But when a major rainstorm hit late on a Saturday afternoon in June 2008, the runoff was on track to fill the entire system in just 56 minutes. District managers had to divert combined wastes into area waterways and reserve the deep tunnels to retain separated household wastes, which also overflowed as the storm continued over the next three days. To prevent that kind of mess in the future, the district is now spending $300 million to preserve open space along local waterways. It also recently paid market prices to remove 75 homes in a downtown neighborhood, adding the land to a city park that doubles as a flood retention pond.

Likewise in Philadelphia, a 2009 study compared gray CSO prevention measures (adding more deep tunnels) with a green infrastructure approach that aimed to halve the runoff from existing impervious surfaces at roughly the same cost. Stratus Consulting, based in Boulder, Colo., estimated that the gray approach would produce $122 million in benefits over 40 years after subtracting construction costs. For the green alternative, the net benefits added up to $2.8 billion—more than 20 times as much—including improved property values, increased recreational opportunities and avoided heat-stress deaths. 

Those kinds of numbers have attracted widespread interest. For instance, an innovative proposal from the Center for Neighborhood Technology in Chicago would fund tree planting and other green infrastructure programs with municipal bonds based on the projected increase in real estate values and tax revenues such programs produce. But there has been only cautious interest so far because it’s unclear whether enforcement officials at the Environmental Protection Agency will accept green infrastructure as a tool for CSO prevention. Even so, Philadelphia recently launched the largest green infrastructure program in the country to transform the city over the next 20 years at a cost of $1.6 billion. (Aquatic biologist Gerald Bright ’08 is coordinating part of the river restoration work.) The city is also adjusting its water and sewer fee structure so that commercial users pay, in part, based on a property’s impervious surface area—a measure of stormwater runoff. Howard Neukrug, director of the city’s Office of Watersheds, described the program as an attempt to “break down some of the barriers against nature and deal with rainwater where it lands.” Despite reservations about the cost, The Philadelphia Inquirer summed up neighborhood response this way: “What’s not to like about cleaner air, cooler houses and prettier streets?”

The Rise of Urban Ecology

This idea of using trees to remake cities and neighborhoods on more natural lines reflects a modern urban ecology movement that got its start one fall day in 1988. An F&ES professor named Bill Burch had just delivered a talk about the community-based forestry program that he was helping to develop in rural Nepal, when a member of the audience, Ralph Jones, demanded, “Why are you not doing that here in our cities?” Jones had just become director of Baltimore’s recreation and parks department, and the two men quickly came to an agreement. Soon after, Morgan Grove, a student in Burch’s community forestry class, got the word: “You’re going to Baltimore.” Burch remembers posing the proposition more diplomatically: “Boy, do I have an offer!” He promised Grove and other F&ES interns who followed that “they would learn more about participatory forestry and how it all works” in three months in Baltimore than “in 10 years in the Mt. Hood National Forest,” and he adds now, “I was right.” 

Bill Burch
Dana Keeton
Bill Burch promised his students that “they would learn more about participatory forestry and how it all works” in three months in Baltimore than “in 10 years in the Mt. Hood National Forest.”

Burch became the first director of the new Urban Resources Initiative (so called “because the president of Yale at that time did not want any more institutes”), and his students were soon collaborating with city staff and community groups to develop the first strategic plan for Baltimore’s parks. Participatory forestry meant getting local people invested in improving their own neighborhoods. So among other early efforts, URI interns helped enlist youth groups to clean up and restore the 14-mile-long Gwynns Falls-Baltimore greenway. They also developed the city’s first neighborhood tree steward program. In 1991, URI added a New Haven counterpart to its efforts in Baltimore. The idea in both cities, says Burch, “was to use natural resources as a means for rebuilding neighborhoods that had lost most of their social capital, only we did not have that buzzword available then.” At a time when other scientists scarcely thought of cities as ecosystems at all, URI brought an interdisciplinary team of social scientists, foresters and hydrologists to bear on urban neighborhoods, with a dual emphasis on people and watersheds. Burch wanted to get past the image of parks as “elitist conceits.” Instead, the parks, together with improved street plantings and rehabilitated vacant lots, would be the means for simultaneously addressing issues ranging from community spirit to the state of local waterways. 

“The idea was to use natural resources as a means for rebuilding neighborhoods that had lost most of their social capital.” Bill Burch

It was the beginning of a move away from old-style “urban forestry.” That term had been around since the late 19th century and gained currency in the 1960s after Dutch elm disease raised public awareness of the importance of city trees (and cost New Haven its reputation as the “Elm City”). The U.S. Forest Service had started paying attention to urban areas for the first time in the 1970s. But the result was at best a holding action—underfunded, narrowly focused on improving municipal maintenance of street trees and utterly overwhelmed by the rapid pace of urban change. By the late 1980s, the average city was losing four trees for every one it planted, according to a study by the conservation group American Forests. The average life of a downtown street tree was just 13 years. Even after a sharp rise in U.S. Forest Service spending for cities, up from about $2 million a year in the 1980s to as much as $25 million in the 1990s, the results continued to be frustrating, according to Gary Moll of American Forests. Only a few states had urban forest councils, and funds tended to get widely dispersed without much thought about where tree planting could produce the biggest benefits. That’s now changed, says Moll, with the U.S. Forest Service holding back a substantial portion of funds to award on a competitive basis “to a few great projects.” But he figures that cities are still losing three trees for every one they plant.

The shift from thinking about urban forests to urban ecology happened in the late 1990s. Grove had gone to work for the U.S. Forest Service in Baltimore in 1996, the day after defending his doctoral thesis at Yale. Federal officials soon began looking at URI’s work in Baltimore as a model. The Forest Service had customarily funded long-term research (LTR) projects in natural settings around the country. But it had never attempted such an ecosystem study in a city—and wasn’t all that keen on trying. (Some old-school Forest Service types still kid Grove about his job title—research forester: “You’re a social scientist. Get out!”) But the work begun by URI in Baltimore demonstrated that you “could really do” serious ecosystem research in a city, says Grove, using standard scientific tools like vegetation study plots, forest inventories and hydrology. In 1998, the National Science Foundation (NSF) agreed to fund the nation’s first urban long-term research sites in Baltimore and Phoenix. And once the NSF had conferred legitimacy on the field, ecologists finally began to think that such a thing as urban ecology might actually exist. 

Urban forests, it turns out, are as rich and complicated as any other forest, and possibly more so because they’ve undergone such dramatic transformations. Conventional wisdom from rural areas holds, for instance, that vegetation buffer zones along rivers and streams automatically filter out nitrates and other pollutants. But in Baltimore, an early LTR study found that urbanization had changed the hydrology so much that polluted runoff was traveling below the root zone of riparian trees and reaching waterways unfiltered. “That was a big ‘Aha!’ moment for policymakers,” says Grove. They switched the focus for tree planting from riparian zones (the endpoint for runoff) to the city-at-large (the source) as a more effective way of dealing with both the quality and quantity of runoff, and they set a goal of doubling Baltimore’s tree canopy cover to 40 percent. 

Studies in Baltimore and other cities also turned up surprising pockets of biodiversity, sometimes including rare or endangered native species. (The discoveries included a new earthworm species in Baltimore, and a German study found more native plant diversity in one city than in nearby rural areas.) An LTR ecologist, Paige Warren of the University of Massachusetts, is now working on a theory that 35 percent canopy cover is a threshold at which a Northeastern U.S. city can start to see more woodpeckers and other forest birds, rather than just the drab urban generalists like sparrows and pigeons. She’s developing guidelines to encourage this transition by keeping some dead trees and branches intact in areas where they don’t pose a hazard to residents. Despite the perception that having songbirds in the backyard is a “luxury good” of little relevance to people living on the poverty line, the LTR researchers found that residents in poor areas are well aware of what they’re missing. Like their counterparts in leafier neighborhoods, says Warren, “they’re more satisfied with places that native birds are more satisfied with.”

But the new urban ecologists have also found that deciding how and what to restore is rarely simple. It isn’t about bringing back the forest primeval. In New York City, for instance, “million-tree” planners have had to omit many of the original native tree species because they are susceptible to introduced Asian longhorned beetles. The new trees must also do obvious, but unnatural, stuff like thrive in areas where the soil is compacted or tightly hemmed in by concrete. Moreover, it isn’t enough for city trees merely to look pretty. Like city people, they’re under increasing pressure to multitask, delivering a variety of “ecosystem services” beyond biodiversity. The right trees planted in the right places can shade buildings in summer and reduce energy demand. But done wrong, the planting can have the opposite effect. Likewise, trees can help reduce pollution by pulling components of smog out of the air. But certain trees, like eucalyptus and oak, produce volatile organic compounds to defend themselves—and in some settings they can actually make the smog problem worse. With those kinds of complications in mind, NSF and the U.S. Forest Service together are now building on the Baltimore and Phoenix studies to develop a network of nine urban LTR areas around the country.

Springtime in the City

If urban ecology means thinking of trees as the means of manipulating big stuff like air, water and climate, it also means using them to change individual lives. Both halves of the equation matter, particularly to URI interns who have gone on from Baltimore and New Haven to work in cities around the world. (They now constitute what Grove calls “a Yale urban ecology mafia.”) “I used to work in Baltimore in the early 1990s, going out to plant trees with recovering addicts, folks who were homeless,” says Erika Svendsen ’93, “and they’d say, ‘I did this when I was 15, and I felt so good.’ These kinds of memories don’t extinguish. The success isn’t that you get somebody to be a tree pruner for the rest of their lives, but how they live those lives, their perspective on the environment.”  

Svendsen’s now a U.S. Forest Service social scientist, tracking the shadow government of community groups and volunteers who do planting and upkeep in neighborhoods around New York City. The stories they tell her are often personal, she says. “‘I started this garden after the loss of my son.’ Or ‘I started this garden because we don’t care much about seniors in this country, and I wanted to do something for them.’ These are the moments when they step out of themselves. It’s a very strong feeling.” For Svendsen, the biggest change produced by the new urban ecology movement isn’t in the landscape. “It’s in here,” she says, tapping her heart. That attitude comes directly from Bill Burch, she says: “He gave me a whole framework, a way of seeing, interpreting, a way of hoping that change is possible, and it lies within people and the environment.” 

James Jiler
Ben Thacker
James Jiler ’95 designed a prison horticulture program for inmates on Rikers Island in New York City.

Burch also taught that those inner changes can produce measurable results in peoples’ lives. For instance, after doing URI internships in Baltimore and New Haven, James Jiler ’95 went on to run a “prison horticulture” program for inmates on Rikers Island in New York City. In an introduction to Jiler’s 2006 book on the program, Doing Time in the Garden: Life Lessons Through Prison Horticulture, a former commissioner of the city’s Department of Correction recalls his reaction when the Horticultural Society of New York first proposed the idea: “Are you insane?” In fact, prison farming has had a long history in the United States. But Jiler designed the Rikers Island program not just to produce crops or provide garden therapy, but to teach things like science, English literacy and basic life skills. A job placement program eventually expanded into post-release training to ease the transition back into society. (That program is the model for the Community Greenspace prison release program started this spring in New Haven.) 

The underlying idea was that tending a garden creates an unspoken contract between the plant and the gardener and draws people into a dialogue with their environment. “With some people it takes a little longer, because they’re battling real hard-core addictions,” says Jiler, who now runs a similar program in Florida. “It’s not like, ‘Now you’re a gardener, you’re going to change.’ I’ve had people that I got really great jobs for, making $35,000 a year with benefits, working for a conservancy, and then they disappeared one day. Something happens in their lives and they go and smoke a bag of crack, and when you find them again they’re in prison.” A recent Columbia University study found that graduates of the Rikers Island program had a 35 percent reconviction rate after three years—and a 25 percent rate for graduates of the post-release program—both significantly lower than the 45 percent reconviction rate for the general prisoner population.

“The success isn’t that you get somebody to be a tree pruner for the rest of their lives, but how they live those lives.” Erika Svendsen ’93

Thus one sunny morning early this spring, with that possibility of change in mind, a half-dozen men from the Crossroads substance abuse program were out planting red oaks, sugar maples and American lindens at West River Memorial Park in New Haven. Long term, the plan is to take a barren corner at a busy intersection and turn it into a forest 70 years from now, when the canopies have spread out and joined together. Short term, a big, bluff, soft-spoken 42-year-old named Leon  said he is just trying to get his life back together. He worked on a red maple and explained how he lost his way after high school. Now he’s trying to break away from his old neighborhood and old patterns of behavior. He hopes to get certified as a substance abuse counselor, he said.

“I love sharing my story, because alcohol abuse and substance abuse kept me in bondage for so long. I feel free when I’m sharing myself with others.”

So does planting trees help?

“This is new, and it’s therapy,” he said. “Anything that’s new—new people, new sights, new colors, new animals—anything new is therapeutic to me. My old way of life was in a box. I didn’t have any expectations. When you’re living the lifestyle that we once were living, you wear a pair of glasses, not literally but figuratively. Whatever we saw through those glasses, it looked like the same thing. Our focus was on one thing. Now I wear a new pair of glasses. I have a new focus.” Then he finished planting the red maple and moved on to the next hole.

All over town, other URI staff and volunteers were also at work, on the theory that planting trees can take people who are already doing fine and make them better, or connect decent neighborhoods in rich new ways. At Clinton Park in Fair Haven, Community Greenspace manager Chris Ozyck was teaching a crew of teenagers and F&ES students how to plant a bare-root tree. Without a heavy root ball, the trees are less expensive and much easier to handle. But they’re also more sensitive. 

“So the stakes go in first,” he said, “to avoid damaging the roots.” One of the teenagers set a tree in the hole he had dug, and Ozyck said, “How do we check the height? Lay one of the stakes across. We’re a little high here. Where is the root flare? Come over and point it out. Good, right where the roots come out.” He adjusted the height so that the roots flared out just below ground level. Then he showed them how to “muddy in” a tree, adding dirt and water alternately and gently probing with the handle of his shovel to release air pockets. By midday, the group had eight trees in the ground, with all the loose dirt raked up and a neat “donut ring” circling each tree to retain water. “If I leave the dirt on the grass, is it going to look like it was planted by a professional?” Ozyck asked. “No, it’ll look like it was planted by a bunch of amateurs.”    

Just up the road at Chatham Square, a Community Greenspace volunteer group was also out doing their spring cleanup. David Zakur, a Pfizer researcher who is a leader of the group, moved to Fair Haven 15 years ago from a 20-acre horse farm in North Madison. He didn’t know that the Quinnipiac River was two blocks away from his new home, and he thought that the only way to get downtown was by taking a car on I-91. Greenspace gave him a way to discover the city and connect with his neighborhood. He married another Greenspace volunteer. Their 18-month-old, Cole, now often joins them on planting days. 

“The whole angle for doing URI,” said Betty Thompson, another volunteer at work in the Cedar Hill neighborhood, “is if you make it clean, keep it clean and have tree-lined streets, then you have less crime, less prostitution and fewer people who just want to hang out and be a nuisance. How has it worked out?” She laughs. “It’s still a theory, okay? But I think it’s working.”

Then she added, “What we’re trying to have here is a better quality of life.”

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