Cities contain too many perfected, simplified forms of nature, ones that look pretty but are biologically impoverished.

If only all cities had forests like the one that slashes through Dallas. At 6,000 acres, the Great Trinity Forest is one of the largest urban woodlands in the United States, an expanse of hardwood trees, ponds, swamps and meandering creeks.

It is not its size that is remarkable so much as its wildness. Neglected, ignored and abused for years, much of it has become an impenetrable thicket with a dense understory that teems with wildlife — feral hogs, turtles, white-tailed deer, beavers, otters and alligators — all at a short distance from the skyscrapers of this very corporate American city.

Cities often contain perfected, simplified forms of nature, ones that look pretty but are biologically impoverished. But forget parks, neat and tidy as they are. Nature at its insurgent best insinuates itself in the gaps in the urban fabric: the soggy, unloved floodplain of Dallas, but also abandoned lots, roadsides and intersections, railroad lines, mortared walls, empty malls, disused factories, the edges of chain-link fences and the cracks in the concrete.

This is where we find the rough, tough vegetation and wildlife, adapted to living in proximity to us, seemingly against the odds. It is not the nature you might find in a national park, and that is why it is worth celebrating: for its sheer ability to survive and thrive in a hostile environment and nurture other life.

Every city has acres of in-between land that, if managed well, could become oases of greenery harboring insect, bird and other animal life. And with cities still reconfiguring themselves in the wake of the pandemic, the case for rethinking their purpose and potential could not be more urgent. We need to make urban areas more walkable, more fun and more livable, to be sure. But we should also make them greener. The city must be not just a place of wealth generation, culture and activity, but also a unique ecosystem that offers us protection against climate threats and a vital, visceral connection with wildlife.

Among the first to document the exuberance of urban ecosystems were casual observers and curious botanists in war-torn Europe in the 1940s. The rubble-strewn cities of World War II, to the astonishment of their inhabitants, very quickly brimmed with plant and animal life. The vegetation that emerged from the debris was totally unexpected, a cornucopia of exotic, often nonnative species that were adept at exploiting and thriving in the damage. Blitzed areas of London brimmed with pink swaths of rosebay willow herb — “bombweed,” as it was nicknamed. In central M?nster, Germany, piles of rubble were veiled with spontaneously growing pussy willow, mountain maple, birches, yellow mulleins and wild strawberry.

These disaster-loving plants often evolved on coastal cliffs, arid mountainsides and other inhospitable places: pioneers of nature that reclaimed scarred territory and prepared the way for larger shrubs and woody species. They had come to the city accidentally over the centuries, concealed in shipping containers or as hitchhikers on the tires of vehicles and the soles of boots. And they had been there, biding their time, until the destruction of war allowed them to run riot and make bombed-out cities look amazingly verdant. They became the key components of a distinctively novel and amazingly diverse urban ecosystem.

It was in West Berlin in the 1950s that urban ecology became a science. One of its earliest pioneers, the botanist Herbert Sukopp, noted that the city’s ecology was in continual flux as nature responded to changes in the human-made environment. Neglected sites were profuse in biodiversity, often containing many more species of plants and insects than nearby parks or even the countryside.

Today in Berlin, a patch of wildness called the Natur-Park S?dgel?nde has bloomed in what was once among the city’s busiest railroad yards. Like the Great Trinity Forest, first it was abandoned and then hundreds of species took over, many of them endangered. But in contrast to Trinity, its wildness is now carefully stewarded. Elevated metal walkways give visitors access without disturbing rare flowers and ground-nesting birds; pockets of precious grassland and meadow flowers are protected by mowing and grazing sheep.

This is a work of intention rather than simple neglect; the S?dgel?nde is biologically successful because it was unplanned. But, paradoxically, it has remained successful because humans now play a superintending role, managing it for both our needs and biodiversity. It is a model for how we can integrate wildscapes into the cityscape.

Imagine a city latticed with lightly cultivated wild spaces, microforests and roadside meadows. (For that matter, imagine the manicured neatness of suburbia blooming with wildlife gardens in place of ecologically impoverished, pesticide-soaked lawns.) That would be a different kind of city, where the human and the natural coil together and where the conventional cityscape is visually enriched by exuberant wildlife.

In the English city of Sheffield, the landscape architects Nigel Dunnett and James Hitchmough chose plants that thrive in disturbed, acidic, dry and nutrient-poor urban environments for densely planted, low-maintenance, self-generating meadows that are the opposite of carefully groomed urban parks, but no less beautiful. In the Netherlands the new policy of Tijdelijke Natuur (Temporary Nature) encourages landowners to allow habitats to establish themselves for a limited period on lots destined for development. The practice acknowledges cities as places that continually create, destroy and recreate areas of biodiversity. Freshkills Park on Staten Island went from the world’s biggest garbage dump to a self-generating habitat largely through natural processes, proof that urban space can be returned to the bald eagles, ospreys, herons and grasshopper sparrows that long ago inhabited the terrain. And the roof of Chicago’s City Hall has become a kind of aerial prairie, with 20,000 plants selected for their ability to withstand sunny, windy and arid conditions. The roof garden cools the building during summer and absorbs a huge amount of storm water.

If cities are to survive a hotter, wet, less predictable climate it is in their interests to strike an accommodation with nature. Urban centers like Louisville, Ky., denuded of tree canopy and foliage, can be 20 degrees Fahrenheit hotter than the lusher surrounding areas. Green spaces offer another form of much needed protection from the elements.

New York, which spent the 20th century remorselessly filling in and building over its tidal marshes, is waking up to the fact that wetlands are the surest defenses against storms and rising sea levels. Hunter’s Point South Park in Queens now has a constructed tidal marsh; parts of Staten Island and Jamaica Bay, among others, are reverting to marshland. This signals a recognition that green infrastructure must be part of the plan to protect the city alongside hard engineering projects.

The priority for New York in the 21st century is to “restore and sustain a mosaic of habitats within the human-dominated landscape” in order to rehabilitate the wider ecosystem. Those are the words not of an eco-warrior, but the U.S. Army Corps of Engineers in a 2020 report. And it is true for all cities battling the effects of climate change. Happily, from Dallas’s Great Trinity Forest to New York’s Freshkills Park, wildness is becoming a pronounced feature of modern cities.

Understood and appreciated, it can bring us deep pleasure. We should embrace it and learn to love the curious, unpredictable hybrid ecosystem that sprouts from the concrete.

Ben Wilson is a historian and the author of “Urban Jungle: The History and Future of Nature in the City.”

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