The Case For Reforesting Our Cities

I grew up in a curiously wild city.

When I was a kid in the north suburbs of Toronto in the 70s and 80s. I lived a few blocks from one of the city’s famous ravines.

Toronto, as it turns out, is built on a huge network of these geologic formations. The city sits atop a 42-square-mile network of streams and rivers that cut through the city like the fingers on a hand, each one nourishing a thick forest on its banks.

If you flew over Toronto and looked down, the amount of greenery is astonishing: It looks like they’ve snuck a city in amongst a massive park. That’s how extensive the ravines are.

At the time, I took the ravine near my house for granted. I didn’t realize how remarkable it was that I could live in a developed suburb — wall-to-wall carpeting, color TV, nearby bus and subway system — and yet be able to walk three blocks and boom, get immersed in nature.

And it was verdant, dank, gothic nature! When I’d walk over to clear my head after doing homework in the evening, the thick canopy of oak and maple trees — with leaves the size of dinner plates — would cradle me in velvet dusk, and silence all city noise. 

I’d hear nothing but the call of night birds and the burble of a creek that, during the spring’s snowmelt, would transform into a frothing torrent. Raccoons would peer down from the trees. I was in a city of millions, but alone with my thoughts.

I bring up these memories because I’ve been reading lately about cities and climate change.

As city planners ponder the fate of our cities under global warming, they’re needing to figure out ways to adapt to serious weather challenges. We’re facing down climate shifts that will tear at the urban fabric.

But what they’re realizing is that, hey, one of the best ways to make our cities more resilient? Make them more wild.

Consider the first big challenge we’re going to have in US cities: They’re going to get hot.

By some projections, American cities will be 8 degrees hotter by 2100, with some feeling more like the Middle East. Part of the reasons cities will get hit so hard is the "urban heat-island effect": Paved surfaces soak up heat and radiate it back, so the city can’t adequately cool down.

One crucial way to fight that? With tons of trees.

An urban tree canopy has a remarkable ability to keep a city cool: Between offering shade and "evapotranspiration" (transferring ambient water into the air), trees can reduce a city’s temperature by 12 degrees Celsius, research shows. Trees also help clean the air.

When I spoke to urban foresters across the US a few years ago, they told me they were working hard to figure out which trees they could plant that would thrive in the hotter decades to come — so that they’d be putting out maximum shade.

Better yet, some cities are working hard to plant more trees in poor black and brown neighborhoods, which in decades past had been ignored by civic tree-planting departments (with the upshot that these days they have less shade, worse air, and hotter peak days than in well-treed wealthy neighborhoods).

On top of the heat, climate change is going to mean huge dumps of water that cities have to deal with.

Precipitation patterns are becoming "bursty." We’re seeing longer periods of dryness, punctuated by epic dumps of rain and snow.

This bursty precipitation is terrible for cities.

Most urban sewer systems were built back when precipitation came in a more steady, regular pattern, so sewers weren’t designed for these massive surges. That means that when a climate burst arrives, they overflow and flood streets, houses, and parks, causing billions in damage.

But this is, again, where adding more wild spaces in a city can help out. Urban planners are identifying little nooks of asphalt that aren’t being used — and they’re ripping them up, replacing them with earth, grasses, bushes, and trees that can absorb water, reducing the risk of flooding.

Other towns are taking a page from the Dutch concept of "room for the river."

They’re adding waterways and ponds that are designed to accommodate periodic floodwaters — and re-engineering their roads so that when they flood, they route the water to these spillover bodies, and vice versa.

They’re also filling greenspaces with native grasses that are fabulous at soaking up excess water.

The idea is to create a city that can flood gracefully, then exhale the water back when the flooding is over. Adding more nature is a key part of that; asphalt can’t absorb water.

This is pretty much how the creators of Babcock Ranch, down in Florida, designed their community. It’s so resilient that when Hurricane Ian pounded Florida back in 2020, Babcock Ranch stayed inhabitable and lights on, even as nearby towns were basically destroyed.

Another big upside of putting more wilderness back into cities? It increases habitat for pollinators.

Over the last decades, suburban sprawl and mega-framing practices (using tons of fertilizers, tearing out wild plants roadside so crops can be grown right up to the highway) have decimated the habitat for America’s pollinating insects.

As climate change brings new pests into new regions, the challenge to native pollinators is getting worse and worse.

So this is a place where cities, too, can do their part.

If we stopped worrying about having perfectly manicured lawns and parks and instead cultivated wilder landscapes — filled with towering native grasses and local flowers — we’d get a two-fer: Very cool-looking towns and cities, filled with habitats that keep pollinators thriving.

And last (but not least), rewilding our towns, cities, and suburbs would be good for the human spirit.

I’ve written previously about "biophilia," the profound joy that we humans get from being near nature.

The science here keeps stacking up and up. Studies increasingly show that when we’re exposed to nature, we sleep better and get more creative; children learn better, and the sick heal more speedily.

These psychic benefits are precisely what I found, all those decades ago, when I was sneaking off to hang out in my local ravine in Toronto. It was a refuge; a place to collect my thoughts; or simply to hang out with my friends when we grew bored of 80s TV and wanted something that stimulated us in a less jittery fashion.

Making our cities wilder will improve the resilience not just of our infrastructure, but our souls.

Clive Thompson is a contributing writer for the New York Times Magazine, a columnist for Wired and Smithsonian magazines, and a regular contributor to Mother Jones. He’s also the author of Coders: The Making of a New Tribe and the Remaking of the World, and Smarter Than You Think: How Technology is Changing our Minds for the Better.