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It seems unnatural to think of cities as part of nature. But environmental resilience depends on it.

Imagining and creating better cities requires seeing cities as nature, not separate from it.

Travis Constantine for the Boston Globe

Like many nature-loving parents living in a city, I’ve tried to teach my daughter about the natural world by taking walks in the woods, learning about pollinators, and looking for signs of spring in neighborhood yards. But the nature lesson I’m most proud of came when my daughter, then 3 years old, looked out at the Boston waterfront, pointed to the distinctive egg-shaped digesters of the Deer Island Wastewater Treatment Plant, and told her grandmother: “That’s where my poop goes.”

Knowing the intricacies of her sewer system might not seem like communing with nature. But our days spent watching hermit crabs scuttle through shallows at low tide in Dorchester are only possible because of it. When I talk with people who lived in the city before the treatment plant, they remember how the Boston Harbor smelled on its worst days. Only by investing in new sewage infrastructure could we make connections with nature in the harbor possible — and allow other species to flourish.


Lessons about urban ecology often ask students to consider only the natural components of cities: to gather leaves, examine bugs, identify birds. These activities certainly help kids connect with a world beyond themselves. But it’s less common to teach about what makes urban environments unique: where drinking water comes from, how runoff courses through storm drains, or how buildings, roads, electrical lines, and other infrastructure interact with nature and create a new habitat for us. When I teach college students, they have a hard time imagining cities as natural environments; they only see nature in the green corners.

This disconnect stems from our persistent notion that nature is separate from the built world, and it has consequences beyond education. In fact, many city dwellers grow up inhabiting an environment they don’t really understand. But imagining and creating better cities requires seeing cities as nature, not separate from it. As ecologist Barry Commoner famously said, the first rule of ecology is that everything is connected to everything else.


The science of ecology came of age with the environmental movement of the 1960s and 1970s, when many people decried how pollution had ravaged natural places such as Boston Harbor. Activism helped spur the creation of the Environmental Protection Agency and a wave of environmental laws and regulations. Ecological science, meanwhile, brought a deeper understanding of the interconnectedness of natural systems and shed light on how human activities interfered with natural processes. But ecology was also shaped by an anti-urban bias that viewed cities as places removed from nature and the source of environmental problems. It was tinged by racial, social, and economic views about cities as lesser environments.

A different view emerged in the 1990s, as urban ecologists began thinking about cities as unique ecosystems, shaped by humans and nature. Urban ecology studies first focused on the ways wildlife, insects, plants, and biochemical processes all manage to live in highly developed and disturbed places. Over time, however, ecologists moved beyond only studying ecology in cities and began to study the ecology of cities: how cities themselves represent unique interconnected systems of natural processes, social forces, and technology. Like natural ecosystems, cities are shaped by the water cycle, the weathering of inorganic materials, the dance of biochemistry that turns one molecule into another. But they are also shaped by infrastructure that modifies those forces. And infrastructure is governed by laws, regulations, technological change, social inequities, and cycles of financial investment.


When we start thinking more about the unique ecology of cities and their infrastructure, we can make positive changes. More than a decade ago, a chance encounter between urban ecologist Nathan Phillips of Boston University and utility compliance expert Bob Ackley led to a partnership to identify gas leaks around Boston. Phillips was wondering how the city’s aging, leaky gas pipes might be harming urban trees, since methane seeping into soil can make its way into tree roots, depriving them of oxygen. The groundbreaking research uncovered an unappreciated source of greenhouse gas emissions in this city and beyond; helped create new coalitions among researchers, environmental activists, and politicians; and led to immediate and ongoing legislative action to address gas leaks across the state.

Gas leaks are an example of how infrastructural decisions affect both nature and people. Subsequent studies have found that sick trees are more likely to be found near leaking gas pipes, and that leaks are slowest to be repaired in neighborhoods with lower incomes or more people of color. Fixing leaky pipes — or better yet, working to eliminate natural gas flowing under our streets and into our houses altogether — not only helps cities and states meet our global responsibility to reduce greenhouse gas emissions, but can improve our local ecosystem and address environmental inequities and public health risks.


Boston also faces the challenge of creating new infrastructure that will help residents adapt to climate change, including increased heat and sea level rise. Many environmental advocates have been arguing for so-called nature-based solutions such as restored salt marshes and living shorelines — vegetation and other natural materials like sand and rocks that protect and stabilize land — along the waterfront. These kinds of solutions represent an exciting opportunity to restore ecological functions to our shoreline that were lost over centuries of urbanization. But it’s also easy to let dualistic thinking slip into categories of green versus gray. Instead, we can reimagine connections between built and natural systems. An example is the Living Breakwaters project near Staten Island, New York, led by SCAPE Studio. Though often described as a restored oyster reef, the project is really a hybrid structure, using painstakingly designed concrete blocks to serve as a habitat for oysters and other marine life while reducing waves and erosion on shore.

There is plenty to critique about cities as environments. Urban centers are hungry hubs of energy use, material consumption, and pollution. They suck up resources and produce an estimated 70 percent of the earth’s greenhouse gas emissions. They face staggering problems related to both social and environmental challenges, from homelessness to heat islands to disease outbreaks. But cities are also miracles of design and construction that allow thousands and even millions of people to crowd into a few square miles of land, raising families, working, eating, sleeping, and moving from place to place in relative safety and good health. That’s why urban areas are expected to house nearly all of the world’s future population growth.


Increasingly, urban ecologists have argued for an ecology for and with cities, applying ecological principles to tackling some of the thorny environmental problems facing urban areas today, including pollution, climate change, and environmental injustice. But to do that, we must go beyond creating complex scientific models of urban systems: we need to help people connect with them.

Many of our environmental problems do not actually require more appreciation for nature, but rather the cultivation of ecological wisdom and a sense of stewardship of the built environment. If residents don’t feel this sense of stewardship, they may fight for trees and green spaces but leave the decisions about infrastructure to engineers, technicians, and other domain experts.

It’s important to me that my daughter spends time in nature — by which I mean in the presence of nonhuman forces like the weather, the growth of plants, and the movements of animals. Being immersed in these forces can instill a sense of awe. But they don’t stop when you leave the park or nature reserve. We can see them at work in plants pushing through sidewalk cracks, the water pouring from faucets, and the weathering of stairs and subway tracks we haven’t maintained. To a child, the inky shine of broken asphalt is every bit as fascinating as a pine cone. I try to fight the instinct to tell my daughter that one aspect of her environment matters more than another. They’re all connected, and I want her to care about all of it.

Courtney Humphries is a visiting assistant professor in environmental studies at Boston College. Send comments to magazine@globe.com.