Recently I began reading my daughter Little House in the Big Woods, the first book in the Laura Ingalls Wilder series that I read devotedly as a kid. The Little House books, which recount a loosely autobiographical story of her family’s frontier life, have received some recent critique, particularly for perpetuating racist stereotypes. But coming back to them, I was reminded of their singular ability to immerse the reader in the details of another world. As a child, I carried mental images from those books that were hard to distinguish from my own memories: making maple candy in a pan of snow, riding in a covered wagon, walking across the Kansas prairie, sweeping the floor of a sod house, sewing dresses from bolts of calico. I could practically taste the salt pork.

But sometimes, instead of imagining what it would be like to be a 19th century frontier girl, I’d reverse things. As I rode in the backseat of my family’s car, I’d imagine that Laura had traveled through time and ended up in the present moment, by my side. I thought about the shock she must feel, as she sat next to me, to be moving so swiftly down paved roads and seeing the gleaming metal cars, traffic lights, parking lots, and strip malls. As her friend, I would explain how everything worked. We use gasoline to power our cars. The streets are all paved now. There are huge supermarkets for food. We have toys made out of plastic instead of rag dolls. Girls can wear pants now!

Looking back, I see that this game was a way of viewing my own world as new and unfamiliar. Imagining that I was Laura’s companion forced me to snap out of the lull of familiarity and appreciate how strange, fast, and big the world was.

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I found a similar fantasy in Deb Chachra’s excellent book, How Infrastructure Works: Inside the Systems That Shape Our World, in which Chachra, a materials scientist at Olin College, looks around her 19th century apartment in Cambridge, Massachusetts. “I occasionally think about what the lives of the people who were in the space before me were like,” she writes, “but I also think about the converse: What if the original occupants of my building came a century and half forward in time to my home in the present day—what would surprise them the most?”

What I think Chachra is trying to do, and what I was trying to do in my childhood fantasy, was to induce a kind of future shock within an everyday experience.

The term “future shock” was coined in the 1970s to describe an intense disorientation or sickness caused by the pace of technological progress. But while it’s common to feel anxious and disoriented by change—the rapid emergence of AI today is a perfect example—we’re actually quite good at letting changing conditions become a new norm, rendering them invisible. Familiar things lose salience. As Chachra says: “Humans are disturbingly good at filtering out anything in our vision that we’re either accustomed to seeing or which doesn’t appear meaningful.” She points out that infrastructure (and I would include just about any part of the built world) is especially susceptible to becoming unseen.

Imagining yourself as a visitor from another time is one way to see the familiar anew. Chachra writes that her apartment’s former residents would be amazed by the amount of clothing and objects in her apartment, how artificially bright everything is, and how washing machines and other devices perform work for her.

As an adult, I learned how Laura Ingalls Wilder’s books, first published during the Great Depression, were motivated by nostalgia for an earlier time and stood in contrast to a world that was advancing toward increasing urbanization, technology, interdependence, and expanding government. Yet the scenarios described in those books also underscored the perils of frontier life, including disease, severe cold, and near starvation.

Sociologists sometimes describe our postindustrial world as a “risk society,” because we are increasingly focused less on dealing with external threats and more on understanding and managing risks that society itself produces: economic downturns, war, nuclear accidents, pollution, environmental degradation, climate change. As a kid, I thought how crowded and even frightening the modern world might look to Laura.

But now I also see how Laura might be struck by how safe and comfortable our built world is. Many of us spend our days within a narrow thermal range and an optimal light level, walk on surfaces designed for human ambulation, drink water that we know is not contaminated, and strain our bodies mostly in exercise classes. As Chachra reminds us, because it has become so mundane to live this way, we forget the sheer amount of energy, materials, and social organization required to create this level of safety and comfort.

It’s easy to accept the illusion that this manufactured world is disconnected from nature, in contrast to the idealized life in the woods and prairie. But the stuff that fills my house and powers my devices comes from somewhere. Every technological innovation embeds us in nature more deeply, but often to far-flung places that supply us with resources and energy.

I’ve written before about how to feel more connected to the built environment by noticing natural processes at work. Another way to foster connection is to break out of the trance of mundanity and let your mind be blown by the built world around you. The purpose of cultivating “now shock” is not just to marvel at technology but to appreciate the materials and processes that shape our world today. The more I stop to notice, to really see what’s around me, the more I understand that letting infrastructure become invisible is a convenient fantasy.

Urbanization is widely recognized as one of the greatest threats to global biodiversity, because it replaces natural ecosystems with habitats built for people. Buildings and roads crowd out forests and grasslands. Water systems are rerouted. Natural plant communities are replaced with landscaping.

But what about the biodiversity of cities themselves? As the world urbanizes, is the living world becoming more the same?

Yes, according to a theory that emerged twenty years ago in urban ecology, called the urban biotic homogenization hypothesis. The idea, as articulated by urban ecologist Michael McKinney, is that cities “homogenize the physical environment because they are built to meet the relatively narrow needs of just one species, our own.” Urbanization replaces native biodiversity with species chosen by or adapted to people and their built environment, leading to similar communities of species, both within cities and across different cities. On a larger scale, the homogenization of suburban and urban landscapes across the US can even create areas that have similar climates and habitat characteristics.

But a recent paper argues that the theory has been oversold, and may actually be unhelpful for understanding how urban environments work.

The urban biotic homogenization hypothesis is simple and makes intuitive sense. It’s easy to see evidence that cities are similar to each other. Turfgrass—the largest irrigated crop in the U.S.—collectively blankets about 2% of its land surface with monocultures of relatively few species. The garden department at your local Home Depot does not offer the rich diversity of a natural ecosystem. Moreover, Home Depots will carry many of the same plants whether they are in Kansas City or Seattle.

I’ve written about this idea in the past, and it made sense when I was working on my book about the natural history of the street pigeon, a bird that populates urban areas across the world. Just like we see the same building types and chain stores in different cities, urbanization—like globalization—could lead to more homogeneous flora and fauna.

But a 2022 assessment of more that 200 studies testing the hypothesis in plants, birds, and other species found that little more than half of studies supported the hypothesis. One problem is that there are many ways of studying and measuring biodiversity. Different species react to urbanization differently. And it is logistically hard to prove such an overarching hypothesis given the time and scale limitations of individual studies.

But in this new paper, researchers Aaron Sexton and Monika Egerer make a more fundamental argument: Urban areas are more complex than the hypothesis gives them credit for, and cities aren’t necessarily more homogeneous than other kinds of ecosystems, like a forest or a lake. You can see a presentation on this work by Sexton, a researcher at Cornell University, here. The paper points out three aspects of urban environments that actually create a lot of diversity.

First, urbanization fragments the environment. Look at urban areas from an airplane, and what do you notice? Grayness, of course, but also structure: roads, blocks, fences, yards. Property ownership divides land into plots, while roads and other infrastructure separates plots from one another. This means that urban habitats are broken up into highly fragmented patches. Highly mobile species like birds can stitch a habitat together from several patches, while others may be confined to their own patch.

Second, urban management is diverse. In my neighborhood of Boston, there’s one house that always has newly-planted bulbs every spring neatly arranged by type and color. This yard is managed to maximize sociality; it’s the one that makes you feel safe and content, like you live in a “good” neighborhood. My neighbor across the street (hi, Betsy!) has had her expansive yard planted in a permaculture style with trees and grasses and native shrubs. It’s also well tended, but designed to maximize natural habitat (it’s also the yard that my daughter most wants to play in). Then there’s my yard, which was planted with showy landscaping by a previous owner but that I’ve gradually filled in with random bulbs and native shrubs, and allowed to be taken over by pollinator-friendly migrants. It’s a kind of palimpsest of strategic planting, natural intrusions, and neglect.

Not only are urban areas patchy, but those patches are little fiefdoms managed with very different ideas, practices, values, and resources. These different ways of managing land have consequences. Urban fiefdoms often lead to high diversity between different sample sites in the same city (called beta diversity). Every time my husband waits an extra week (or two) to mow our lawn, it creates different micro-habitat for bees and other pollinators, which looks very different from the professionally managed condos next door. Overlooked areas in cities—vacant lots, rights-of-way, large sidewalk cracks—can also harbor surprisingly diverse populations of plants and insects.

Finally, urban areas are often disturbed. They are subject to floods, fires, drought, and other kinds of natural disturbances, but also human-caused disturbances. Land is constantly changing hands and being redeveloped. Every time a building is flipped in my neighborhood, the landscaping is ripped out and replaced. Changing policies and social values can shift the way people manage landscapes over time, like bringing more pollinator gardens and xeriscaping into yards.

These three forces — fragmentation, diverse management, and disturbance — act as biodiversity generators within cities that counteract some of the other homogenizing forces. Different cities also have different social histories and land use strategies that create distinct biodiversity dynamics. A city with large areas of parkland like Central Park will generate different types of diversity than one with smaller, evenly-distributed parks.

“In sum,” the paper says, “cities are more than uniform landscapes of turf grass lawns, ornamental plantings, or invasive species.”

In fact, when you start thinking about all the ways that humans and other species interact in urban areas, urban ecology becomes mindbogglingly complex. It is all the dynamics of non-human nature unfolding in a fragmented landscape shaped by human psychology, economics, law, and social life.

This complexity and downright weirdness is missing from the typical depiction of urban nature as a sad shadow of capital-N Nature. Yes, the human footprint poses a huge and overwhelming threat to biodiversity on a global scale by encroaching on ecosystems that can’t coexist with a built environment. And I don’t discount the many studies that have indeed found evidence that urbanization produces similar communities. But the nature we make is also incredibly interesting and more dynamic than we think. Homogenization may be an aspect of cities but not a destiny. We can intentionally support unique patterns of urban biodiversity over sameness.

This week I’m departing a bit from my usual essay on urban environments to announce some news: the publication of my book, Climate Change and the Future of Boston, with Anthem Press. It gives a brief but deep dive into the city’s risks, challenges, and opportunities in a changing climate.

The idea for the book grew out of work by the Urban Climate Change Research Network based at Columbia University, which assesses how urban areas are responding to climate change and collects case studies of specific issues in different cities. This book expands that approach to look at the dynamics of climate action and governance in a specific city, both to understand those dynamics better and hopefully to allow for comparisons across cities.

My approach was also informed by my own PhD research, which examined how the historical management of Boston’s shoreline shapes current planning for future sea level rise. In the book, I look at some of the ways that Boston is influenced by its history, both in terms of the climate risks it faces and its ability to mitigate and adapt to climate change.

If you’re interested in learning more, here’s a recent interview for the New Books Network podcast. If you’re local to Boston or connected to a university anywhere, consider asking your library to buy a copy of the book!

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I’m aware that this book comes at a disheartening time if you live in the United States and care about climate change. The news over this past year has been devastating, including the country’s withdrawal from the international Paris Agreement, federal funding cuts for climate-related projects, and the U.S. EPA’s repeal of its “endangerment finding” recognizing that greenhouse gas pollution threatens human health.

But from my view as someone focused largely on climate action at the local level, there is much to be excited about. Despite federal policy, many cities, suburbs, and communities across the country are moving forward to both prepare for climate change and to reduce their climate impacts. I describe how Boston’s ecosystem of local government, nonprofits, academic research, citizen action, business groups, and philanthropists are helping to push innovation forward despite challenges.

This week, I visited Miami, Florida during Miami Climate Week, where I was an attendee, moderator, and panelist at the Resilience 365 Conference. Boston and Miami are vastly different cities in terms of geography, ecology, culture, politics, economics, and development history. But I heard many of the same goals and challenges that I’ve heard in Boston.

Folks in Miami are acutely aware that they are considered ground zero for climate change in the United States. Miami’s shoreline is held up as an iconic example of urban hubris in the face of risk (as one person told me, it’s always the first slide in every PowerPoint presentation on urban climate change). It’s among the most vulnerable cities to the impacts of sea level rise. Like Boston, one of the most daunting challenges right now is financing new infrastructure without federal support and local willingness to pay for improvements. And advocates are working within a political situation in which the local government, incredibly, can no longer use words like “climate change” or “net zero“ despite the fact that 90% of Floridians believe climate change is happening, higher than the national average.

But local action in Miami is strong. I was able to meet and listen to policymakers, nonprofit workers, academics, and consultants working in Miami and other areas of South Florida to build resilient and efficient housing, create living shorelines in flood-vulnerable areas, seek creative ways to finance resilient infrastructure, and work with communities to restore a better relationship to water. They are doing innovative work to deal with intersecting water challenges, which include coastal flooding, stormwater and river flooding, groundwater and drinking water pollution, and drought. A few years ago, residents, businesses, and environmental groups successfully fought off a U.S. Army Corps plan to protect areas of the city along Biscayne Bay with seawalls, forcing the agency to instead investigate a nature-based approach.

It’s clear that scrubbing a few words from government documents and grant proposals won’t stop this momentum.

I tend to view urban climate action through a broader historical lens of urban development. Cities in the United States and other parts of the Global North that underwent industrialization in the 19^th century faced pollution and public health problems from rapid growth. The response was what historian Martin Melosi called the “Sanitary City”— an infrastructural revolution that led to centralized systems to manage water, sewage, and waste. Sanitary cities evolved to include zoning and environmental regulation to redirect and control pollution. Sanitary cities are successful but also lock in systems that make change difficult.

We are, arguably, in a decades-long transition to new urban forms, guided by a few key visions. The primary vision is the Sustainable City that is less wasteful, more efficient, and runs on renewable energy rather than fossil fuels. Another related vision is the Resilient City that will allow residents to continue to thrive even as our planet makes an unprecedented leap out of the mild temperatures and predictable weather patterns of the Holocene. The Just City strives to make this transition happen in an equitable way. We might also add the Biophilic City that aims to create more nonhuman nature and biodiversity in the built environment.

I see these goals as more than fantasies because I meet so many people working towards them. But I admit that, outside of this world, it can be hard to see evidence that cities are changing for the better. Yes, we have more bike lanes and tree plantings and LEED-certified buildings, but we also have the global challenges of ever-rising greenhouse gas emissions, consumption, waste, income inequality, extreme weather events, and accumulating risk.

Even at the local level, sustainability and resilience projects often fail to live up to lofty expectations. They sometimes benefit wealthy landowners more than other community members, contribute to gentrification and displacement, or simply fail to have an environmental impact beyond giving a company or city government a green-washed marketing tool. That’s why I feel it’s essential to gather data about this work and to support research and writing that takes a critical perspective on urban sustainability and resilience policy and projects (I have contributed to this literature as a journalist and researcher).

Just because something is problematic doesn’t mean it’s not worth doing. It would be hard to imagine an effort as complex as reorganizing a city’s relationship to energy, water, waste, and nonhuman nature without major obstacles and tradeoffs, particularly when this work takes place in an economic and political context favoring money and power. So while I view these efforts through a critical lens, I think their goals are absolutely necessary. I don’t believe cities in the future will match the ideals I’ve described above, but many aspects of urban infrastructure are changing for the better. I’m heartened by the collective energy from people on all sides of the political spectrum to make that happen.

This has been a pretty brutal winter in Boston; we’ve had over 60 inches of snow. Snow banks have lingered, crowding cars and sidewalks and making everyone grumpy (I heard about multiple altercations over parking spots in my neighborhood, including a stabbing). Recent big snows in the Northeast have surprised a region grown accustomed to thin winters. But I’d like to focus on snow’s material companion, its obbligato in the urban environment: salt.

Road salt is used lavishly here. And a large part of winters in Boston is what I’ll call salt weather, that stretch of weeks when there’s no snow, rain, or “wintry mix” as they say here, only cascades of road salt left in anticipation of future storms. With nothing to melt it, the salt grinds to a fine powder under shoes and tires. It billows up along the highways, shrouding traffic in a saline fog. Walking in salt weather leaves an acrid taste on my tongue, like when you squeeze a box of baking soda too hard.

Some years I see more salt than snow. It’s forced me to realize that snow isn’t the material that most heralds winter for me—salt is. And yet we don’t celebrate the first salt of the season, or sell Christmas ornaments depicting salt crystals, or comment to a neighbor that “this is some salt we’re having.” We pretty much ignore the days we spend walking and driving through grainy clouds of dust. In the news, road salt is both celebrated as a beacon of public safety (Boston’s mayor holds a yearly press conference in front of a salt pile) and decried as an environmental harm. I think this cognitive dissonance between celebration and shame makes us ignore the hold salt has on our daily lives.

That’s because salt weather is our own creation. And while road salt is visible only in winter, it is part of a human-driven cycle that brings salt from places around the world into urban areas like Boston, where it remains even after it has washed out of sight.

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Much of the infrastructure supporting the salt cycle is hidden. Every winter in Boston, 37,000 tons of road salt is tucked away into eight storage areas across the city. And when it’s not hidden, it can be controversial. The Eastern Minerals salt pile in the adjacent city of Chelsea, which supplies salt to the entire region, has become a landmark that can easily be seen from the highway as it waxes and wanes throughout the year. Chelsea is the smallest city in Massachusetts but serves as a depot for the region’s oil, gas, and produce, exposing its population—nearly half foreign-born, and 20% living in poverty—to industrial air and water pollution. So the salt pile has been both a critical support to the region and a bane to an already-burdened neighborhood.

To mitigate the impacts of the salt pile and to integrate community and industrial needs, the design firm Landing Studio created the innovative PORT (Publicly Organized Recreation Territory) Park, which includes a shared-use area that is seasonally used for salt in the winter and for recreational space in the summer.

Also invisible is the human labor, energy, and natural environments that support salt piles like these. Our road salt is shipped in from several salt mines around the world, primarily from a vast salt field in Chile’s Atacama Desert, which also supplies a major share of the world’s lithium for batteries. About ten years ago, photographer and artist Allison Cekala traveled to Chile to trace road salt’s journey as it was blasted and processed at a mine, loaded onto a cargo ship, carried through the Panama Canal, unloaded on Chelsea’s waterfront, and picked up by trucks for distribution on the streets. Cekala said she wanted to highlight “human ingenuity, globalization and the raw beauty of the salt.” In the whitish plumes emerging from the mine in her video and photographs, I recognize the clouds forming along I-93 during salt weather, and I’m suddenly able to see how this material connects the two locations.

The images end with salt trucked through city streets. Perhaps the most invisible part of the salt cycle is what happens later, after the snow has melted and the salt gradually disintegrates. Road salt can have immediate impacts, from harming landscape plants to burning pets’ feet. But there’s an ever-growing and alarming body of research showing that accumulating seasonal cycles of salt use has profound impacts on nearby ecosystems, particularly rivers, streams, and lakes.

The most commonly used road salt is simple sodium chloride, but other minerals (calcium or magnesium chloride) are also used, as well as other chemical deicing agents. Road salt makes its way into soil, sewer drains, streams, and rivers, eventually ending up in lakes, groundwater, or coastal waters. Salt concentrations pulse in winter and spring and recede in summer, diluted by rain, but they do not disappear. Over decades of road salt use, urban lakes become many times more concentrated in sodium and chloride. Road salt reshapes habitats and creates new ones.

Northeast highways and major roads are often lined with plants like cattails, seaside goldenrod, and invasive Phragmites typically found in salt marshes. In fact, these human-created linear marshes act as inland pathways for Phragmites to spread. Less visibly, high salt concentrations harm many species from amphibians to fish to invertebrates, and can starve lakes of oxygen. Salt can build up in groundwater and drinking water supplies.

Salt ions are chemically active; they corrode concrete and metal, weathering built infrastructure and releasing metals into the environment. Collectively, the salt and metal ions from deicing lead to a buildup of what University of Maryland ecologist Sujay Kaushal and colleagues call “chemical cocktails” of nutrients, metals, and salts. They have coined the term “freshwater salinization syndrome” to describe how streams, rivers, and lakes in the United States are becoming gradually saltier and more alkaline, in part because of the liberal use of road salts.

The urban salt cycle is driven by a seasonal one-directional flow from natural salt deposits to urban areas. So what happens to urban ecosystems over long periods of time? This is a fascinating question. If urban areas become so choked with salt that we notice the signals of salt pollution more, I believe our practices may shift.

This adaptation is already happening in small ways. Numerous public education efforts try to get homeowners to purchase pet-friendly ice melt or adopt less intensive practices like making a salt brine. Some communities are making decisions to reduce road salt or replace it with products made from organic materials like molasses or beets (the paths of Smith College in Northampton, where I’m teaching this semester, are coated in a brown brine that smells of soy sauce).

While there are environmentally preferable substitutes, the solution would also likely involve scaling back our salt use. And that would mean rethinking the assumption that cities don’t stop for the weather. I live on a steep hill where traction is valuable. Salt allows my daughter to get to school every day. Without it, I would not be able to make the two-hour journey to Smith once a week in this harsh winter. Salt can be a literal lifesaver for people who need ambulances and prescription medications.

Salt is the protective balm of urban life; no wonder we slather it on our roads and sidewalks like sunscreen. But unless we want to leave our children with a much saltier future, the urban salt cycle will need to evolve.

When I was growing up in Albuquerque, New Mexico, most of our family vacations were by car. They involved driving down long stretches of interstate highway to see a national park or visit grandparents in Arizona and California. This was before screen time, and much of the time I stared out at the scenery: distant mountains and plains dotted with chaparral, decrepit roadside shacks, miles of Stuckey’s billboards.

But one of my favorite things to watch was the road itself. In the hot summer, there was a shimmering, undulating pool of what looked like water just at the farthest visible spot on the road. As we moved toward it, it seemed to glimmer and dance teasingly, then shrink to a thin puddle, then just a line of glitter droplets. Then it vanished completely, only to reform at some farther dip in the highway.

I recently thought about these mirages along desert highways in my youth as I was reading through “Asphalt: A History,” by historian Kenneth O’Reilly, which details all the ways that asphalt has literally shaped our world. These days, my associations with asphalt are pretty negative. It blankets land, disrupts ecosystems, contributes to flooding, and exacerbates urban heat (the intense heat generated by black asphalt is what creates the light refraction responsible for highway mirages). Asphalt production is polluting and asphalt roads carry most of the greenhouse-gas emitting vehicle traffic on the planet.1

It’s easy to vilify asphalt as the ultimate harbinger of the Anthropocene, the paver of paradise. But my memory reminded me that asphalt is also, more than just about any material, part of the intimate lived experience of most humans.

O’Reilly puts this more starkly in his introduction:

“Asphalt...is present nearly everywhere we are present, so baked into the tale of our species that it rules even in absence. Too often for those who live where asphalt has not yet spread, there is only mud and poverty or dust and poverty. For virtually everyone else, the only true escape from asphalt is death.”

Think of how much collective time you’ve spent in the presence of asphalt, how many moments it has been in your view, how many experiences it has created, both life-changing and mundane: road trips, shopping trips, basketball games, bike rides, workplace commutes.

I’d like to explore asphalt in future posts about road ecology, urban planning, and material life cycles. But for now I want to pause to appreciate the sheer scale of asphalt’s presence and appreciate how closely it is linked to our lives.

Technically, “asphalt” or bitumen is the sticky substance that serves as a binding agent in roads and is also used to make shingles, coat landfills and reservoirs, and other uses. The road material we often call asphalt is a mixture of a small amount of bitumen or asphalt binder and a much larger amount of sand, gravel, and crushed stone, collectively called aggregate. Bitumen acts like the wet ingredients in your oatmeal cookie dough, keeping the dry ingredients stuck together into a spreadable substance.

Like many of our ubiquitous urban materials, asphalt has a natural form. It is found in places where petroleum has been buried and gradually transformed under high pressure to a sticky, viscous, slow-flowing substance. Asphalt, like all petroleum products, is made of life: largely, ancient single-celled algae and plants that lived, died, and were buried on the floor of ocean and lake beds, and over millennia became mixed into Earth’s geology. It is viscous when heated and collects in underground lakes and tar pits found in Canada, the U.S., Brazil, Trinidad, and other places, and sometimes oozes to the surface as seeps or asphalt volcanoes along the seafloor. Sticky tar pits are one of our best sources of fossil records as they would trap and preserve life, including the bodies of large animals.

Natural asphalts were first used as waterproof coatings, and later were hauled out of the ground and transported around the world as a paving. But mining and transporting asphalt was labor-intensive, and in the late 19th century engineers developed techniques to create asphalt from refining petroleum. Petroleum can be heated and chemically altered to produce cocktails of different hydrocarbons (compounds of carbon and hydrogen) with different properties that collectively shape a great deal of the human-built world.

When asphalt is heated, it releases volatile organic compounds (VOCs), which create the uniquely headache-inducing aroma that seems to go right past our noses and burrow into brain cells and arteries. And yet, depending on your experience, it may not be entirely unpleasant: the smell of asphalt might evoke a sense of progress and industriousness, or, as in the case of those highways I traveled as a kid, the promise of the open road.

The urban environments we have today are completely dependent on asphalt. Its character suits urbanity. It is a physical binding agent that can bring gravel and stones together in a unified substance. It can be heated and spread like peanut butter but then harden into something relatively solid and impenetrable. Although anyone who drives on asphalt roads knows that its solidity is easily cracked, broken, and slumped, asphalt is for a time sturdy and smooth. Think of the moment when you’re driving on an old highway and your wheels suddenly encounter a newly paved surface—that frictionless sensation like when airplane wheels leave tarmac.

Asphalt is a social binding agent too. It is connective tissue that literally joins us together in communities, cities, nations, and civilizations. The image of broken asphalt—whether a potholed urban street, an abandoned rural road, or rubble of a bombed-out city—is a proxy for social and institutional absence. But asphalt is also a social disperser; it connects us to distant places, sometimes at the expense of our own neighborhoods and local environments.

One of the groups who lobbied for paved streets even before the automobile were bicyclists, as asphalt roads made traveling much faster, more comfortable, and less fraught with mud and dust. Paved streets were also easier to clean in times when horses and their manure choked streets. But as O’Reilly explains, early efforts to pave streets in the 19th century were often met with protest, “as pavement would increase traffic volume and speed and thus destroy a street’s dual function of carrying traffic and serving as playgrounds for children and gathering places for all ages.” I find this quote stunning as a parent used to directing a young child through a neighborhood crisscrossed by death-strips. Imagine if the streets surrounding us were still places to play and gather for more than yearly block parties and parades. Asphalt made speed feel like a right.

Asphalt is now a large part of the geology of urban life. And because of that, every aspect of asphalt’s production and use is critical to shaping the urban environment for the better or worse.

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I was inspired by a colleague who had taken a class forest bathing, and I was looking for an excuse to enjoy the warming weather. I planned to walk with the students to a wooded area of campus and spend some time there. But in the end, I crammed too much commentary into our walk (turns out I had lots to say about draconian campus landscaping), and by the time we reached the wooded hill, we only had time for a quick soak before the had to scurry off to their next class.

I told my students to take a few minutes to sit quietly, put away distractions, look carefully at the woods around them, and allow all their senses to take in the environment. And, well…quite a few of them ignored my instruction and chatted on a bench with friends or stared at their phones. But some took it seriously and perhaps felt a moment of connection to nature. If nothing else, they got some fresh air and vitamin D in the middle of a busy day.

One of my goals in this course was to help my students see cities as connected to nature. And doing this exercise got me thinking: Is there an equivalent way to help people feel connected to the built environment? Is it possible to go “infrastructure bathing” right where we are? What would that even look like?

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At the outset, it seems like a ridiculous idea, given that we are already typically surrounded by infrastructure. We can take a literal bath in our homes anytime.

But while the built environment is always present, we’re often not very aware of it. It’s in the background—it is our background. So how do we strengthen awareness and connection to something that is always present? And can doing so help us feel more awake to the reality of our lives?

As I’ve begun to explore this question, I’ll be sharing ideas in future posts for ways to spend a few moments in mindful awareness of our everyday infrastructure, much like forest bathing. For today, I’ll focus on seeing nature through the built environment. The goal here is to break out of the illusion that our built world is separate from nature by observing all the ways it’s not.

Observing nature at home sometimes means appreciating dust gathering, cobwebs collecting, and wind pushing through drafty doorways in ways we usually don’t. Looking around my house, I see diagonal cracks in the 19th-century walls formed when the house settled into yielding earth. When I pour a glass of water, I sometimes stop to remind myself that it’s not appearing in my home like a replicated drink on Star Trek; it has journeyed 60 miles from the forested slopes of the Quabbin Reservoir, through a network of pipes. Outside, it’s even easier to find nature in the built world. Stone and concrete walls in my neighborhood are ecosystems of their own; mortar and concrete act like fertile soil to support interstitial lichens and mosses, while larger crevices fill with plants. Walls, like hillsides, can even develop different communities on north and south-facing sides. Sidewalk cracks, of course, are prone to being colonized by plants.

Signs of nature in the built environment are often seen as an aberration, flaw, or problem that needs fixing. But we can practice seeing them in a more neutral way, with curiosity and interest. What is happening here? How does this work?

Pay attention to how air moves. “The city presents a rough surface to the wind,” wrote Anne Whiston Spirn in The Granite Garden, her classic guide to ecological design that asks designers to become attuned to natural processes in cities. “Building peaks and street canyons, with their abrupt changes in shape, height, and orientation, place a frictional drag on the layers of air closest to the city’s surface, slowing them down.”1 Whether streets run parallel or against the direction of the wind will cause gusts, eddies, and pools of stagnant air. I think of this every time I find myself around Stuart Street in Boston’s Back Bay, which always feels like a wind tunnel. The buildings here are aligned against with larger air currents flowing over this part of the planet.

Water is another example. A heavy rain is a great teacher; many development disasters might have been avoided by simply paying attention where water travels when it rains. When rain falls or snow melts, notice how fast, how slow, how tortuous is the water’s path, and how it interacts with what is built.

Looking at these natural intrusions in the built environment is admittedly different from being in a forest, where the goal is immersion in nonhuman processes. But when I spend a few moments looking at a weed pushing through an improbably narrow sidewalk crack, I appreciate the resilience and boldness of non-human nature as it takes over places that never asked for it.

What I’m describing is a series of momentary observations: infrastructure dips. Since we’re already physically immersed in the built world, the goal is not to escape to a different place but to find a deep, if brief, mental immersion in awareness in the familiar. When you start paying attention to the everyday processes at play in our world, you begin to step out of the illusion that there are two separate realities: nature and us. It is all real and all connected.

Where and how do you pay attention to nature in the built environment?

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What do we lose by seeing ourselves as separate from nature? In my introductory post, I talked about the “human-nature dichotomy” that leads us to draw distinctions between what we build and the natural world. This distinction often breaks down when we probe it, but we rarely take the time to do so. We let it drive our ideas and decisions and actions in the world. The premise of TNWM is to play with and poke at those divisions.

How does our dichotomous thinking shape the way we see the urban world? Let’s start with an example about carbon dioxide.

Carbon is often placed at the center of our climate conundrum. We’ve unearthed and mobilized carbon by extracting and burning carbon-rich fossil fuels, deforesting large areas of land, and engaging in industrial activities like manufacturing. Vast amounts of carbon formerly locked within slower-moving systems have been transferred to the atmosphere, largely as carbon dioxide, which, along with water vapor, methane, and other greenhouse gases, knits together an ever-denser blanket of gases that heats up the planet.

Reducing greenhouse gas emissions from these activities is the most critical action we can take to slow this process. But analyses find that meeting global policy targets for greenhouse gas emissions would require “negative emissions,” which means pulling carbon dioxide out of the atmosphere, not just reducing what we emit. Hence the widespread interest in understanding “carbon sinks,” systems that absorb and trap carbon dioxide in places other than the atmosphere.

On a global scale, natural systems like forests and wetlands represent a huge carbon sink, since plants breathe in carbon dioxide and use it to live and grow, locking carbon into cell walls, roots, stems, trunks, branches, and leaves.

So what about urban environments? The notion of nature as a “carbon sink” has infused urban environmental planning, supporting efforts to plant more trees and create more green space. Carbon sequestration becomes another reason for valuing nature in cities. And it lets environmental advocates put nature in the language of urban planning for climate change and public health, which gives it more weight in human decision-making.

Urban areas are a hybrid of built “gray” and natural “green/brown/blue” features. When we view humans as the problem and nature as the solution, it’s easy to look around urban environment and think of gray stuff only as the carbon “source” and natural stuff as the “sink.” But what actually happens to carbon dioxide in urban environments?

It turns out that “gray stuff,” particularly concrete, is interacting with the environment in complex ways. Concrete, for instance, is a mixture of cement (a binding agent made from mined inorganic materials) and sand or gravel. The resulting material is speckled with pinpoint pockets that soak in rain and absorb air. As air defuses into these spaces, it reacts with cement to form new products called carbonates. This process, called carbonation, traps carbon dioxide inside the cement. So concrete sidewalks and buildings are, in their own way, breathing carbon dioxide from the surrounding air.

What does this look like at a larger scale? It depends on how much concrete is around. A 2021 study estimated that buildings in a dense section of Shenyang, China sequester 1,701,600 tons of carbon, equivalent to more than 4% of the city’s emissions, at a rate higher than natural carbon sinks of the same size1. Another study estimated that globally, cement materials sequestered enough carbon dioxide between the years 1930 and 2013 to offset 43% of the carbon dioxide released into the atmosphere by manufacturing cement over the same period of time. In other words, over large spaces or long periods of time, those porous, cinereous surfaces of sidewalks, bridges, and high-rises help to reshape the urban atmosphere2.

Cement is one of the biggest sources of greenhouse gas emissions globally (fossil fuels are also used to manufacture them), so there’s no environmental case to be made for making more concrete. But studies like these highlight how the built environment is not inert and separate from processes in nature—it is part of the ecological fabric of urban areas.

Carbon-wise, urban greenery is also more complicated than we typically give it credit for. Natural ecosystems also expel carbon dioxide as microbes munch up decomposing plant material in soils, a process called respiration. Research on urban soils in the Boston area where I live found that they tend to release more carbon dioxide than rural soils, in part because people love to rev up soil bacteria by feeding them fertilizer and compost and piling mulch everywhere3. Simply calling any urban green space a carbon sink overlooks this complexity. Numerous studies have found that carbon shuffles in and out of landscaped spaces differently depending on what is planted and how it is cared for. A study in Finland found that it can take years for a street tree to turn into a carbon sink rather than a source4.

I would never argue that we don’t need more vegetation and green spaces in cities, because living organisms are so much more than carbon banks. Neither buildings nor urban trees can offset the emissions we make (which is why reducing emissions is critical), but they do matter. How can we manage the processes of manufacturing, building, repairing, demolishing, and rebuilding our infrastructure to enhance carbon sequestration? How might we manage urban green spaces differently to enhance their ability to store carbon? These questions are actively being researched. Answering them will take a lot of measurement and modeling, but it begins with a leap of imagination.

If we envision a city in which buildings are spewing pollution and trees are sucking it up—the image I see constantly in urban planning—we are seeing only part of reality. The entire urban area is complex and dynamic. This makes planning more challenging, but it also opens up new possibilities for remaking urban areas with connections to the larger environment in mind.

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When you look around your immediate environment, where do you see nature? If you live in an urban area like me, you might see it in your front yard, or a local park, or street trees lining your neighborhood. But what about the streets themselves? Or your house? Or the underground sewer and gas lines that you depend on?

A couple of years ago, I wrote an essay for the Boston Globe Magazine articulating an idea that had kicked around in my mind for years: The belief that we are separate from nature is at the root of a lot of urban problems. When we teach kids about urban ecology, for instance, we emphasize the living stuff in cities, like maples, robins, and squirrels. We talk less about sewer systems and energy grids, how they work and how they interact with natural systems. This is the thought that put me on the path to create this newsletter.

Why write a newsletter about nature focused on urban areas? This is a question I’ve often asked myself.

If I think about the places that have had most significance for me, it’s almost always somewhere non-urban. The stillness of the Utah desert in Canyonlands National Park. The soft azure waters in Havasu canyon. A moment in my adolescence looking across a snowy hillside in New Mexico. Staring at the ocean along the coasts I’ve visited in my life.

If I’m honest, a big part of me has never been a city person.

I’ve always imagined myself living away from a city—someday. Yet here I am, middle aged and still living an urban life. Not just living it, but writing about it, studying it, making urbanity my life’s work as a writer, researcher, and educator. I might have pursued opportunities to live closer to nature or to build them into my writing and research. Instead I chose to focus on topics like urban nature, urban ecology, urban climate change planning. Why?

What I’ve been circling around, I realize, is not just an intellectual curiosity about cities but a desire to see something in them beyond the obvious, and a belief that they can be more than we give them credit for. That is, in many ways, what The Nature We Make is about.

I came to this realization while trying to declutter my bookshelves. Buying a book is always an act of optimism: whether the book lives up to our expectations or not—whether we even find time to read it—the choice signals the kind of insight we hope to find. Looking over the books I’ve collected over the past quarter-century, it’s clear I’ve always gravitated to writing that plumbs the connections between cities and nature. Mine are always about urban nature, histories of places, and ideas and theories about urban environments.

Many years ago, I wrote my own book about the natural history of pigeons with this goal in mind: how to see an urban bird that is often denigrated as part of nature. The book, Superdove, allowed me to poke at what’s sometimes called the human-nature (or nature-culture) dichotomy, the idea that humans are separate from nature.

There was a flurry of scholarship in the late 1990s and early 2000s that challenged the human-nature dichotomy from many disciplinary angles: urban ecology, geography, environmental history, philosophy. This academic literature, while very cool and worth reading, has not necessarily permeated our day-to-day thinking. And, you might argue, it’s an esoteric debate.

But I believe that our mental separation between people and nature matters. It keeps us from fully understanding our world and fixing environmental problems. And it leaves us feeling disconnected from the places we inhabit. As I wrote in the Boston Globe piece, “many city dwellers grow up inhabiting an environment they don’t really understand.” That has real consequences. I concluded that we don’t necessarily need to connect more with nature to solve our environmental problems: we need to cultivate “ecological wisdom and a sense of stewardship of the built environment.” Otherwise, we leave all the decisions about infrastructure to engineers and planners rather than fighting for them as we would fight for trees and parks.

Lately, I’ve wondered: Why is it so hard to feel connected to the urban environment around us? Can I learn to appreciate it in the same ways I appreciate those wild places? Can I better appreciate the profound differences by seeing both of them as vital and interconnected?

This is the challenge I’m taking up in The Nature We Make. Some of the questions I plan to explore are:

How do urban environments work? I’m looking at surprising ways that our human-shaped built environment interacts with the natural one.

How can we see and understand our environment in new ways? I’m drawing on data and science to answer questions, but my ultimate aim is to pursue connection.

How does this understanding open up new possibilities of action? This is not about easy technological fixes. It’s about perspective. I believe that the way we frame our reality shapes the solutions we see as possible.

This post was originally published at https://thenaturewemake.net.

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