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The Concrete Jungle Is Turning Green Again

This story is adapted from Supertall: How the World's Tallest Buildings are Reshaping Our Cities and Our Lives, by Stefan Al.With urbanization often comes the concrete jungle, a crowded forest of skyscrapers shrouded in air pollution and surrounded by filthy rivers. The 19th-century epitome, London, had its River Thames filled with putrefying carcasses, human waste, and rotting sludge. One hot summer in 1858 exacerbated the already foul-smelling scent to such an extent that it went into the history books as the Great Stink. Today, science fiction often depicts the “urban” as a dystopian, dense city of asphalt, where not a single tree or blade of glass is to be found. Think Blade Runner, its urban scenes permanently dark and overrun by buildings.The underlying assumption is that with economic growth comes environmental decline. And this is not too far from the truth. Even a nightly satellite view of the Earth shows urbanized areas as bright swaths of light. From above, darkness is a good thing, referring to nature, unlit. Inside these supernovas lie only a few patches of pitch blackness. The bigger the city, these images show, the less green there seems to be.

But some cities are fighting back on this narrative.

As early as the beginning of cities, those cities that debased their natural surroundings did so at their peril. In 3000 BC, Uruk was more densely populated than modern-day New York City, with 80,000 people crammed into an area of a little over 2 square miles. This crowded capital had to continually expand its irrigation system to feed its growing population. In Sri Lanka 2,500 years later, the city of Anuradhapura had a similar problem. It was also growing constantly, and like Uruk, it relied heavily on an elaborate irrigation system.As Uruk grew, its farmers began chopping down trees to make space for more crops. Initially, Uruk’s expansion worked well. However, without trees to filter their water supply, Uruk’s irrigation system became contaminated. Evaporating water left mineral deposits, which likely rendered the soil too salty for agriculture.In Anuradhapura, however, trees were sacred. Their city housed an offshoot of the Bodhi tree under which Buddha himself was said to have attained enlightenment. Religious reverence slowed farmers’ axes and even led the city to plant additional trees in urban parks. Anuradhapura’s irrigation system was designed to work in concert with the surrounding forest. Their city eventually grew to more than twice Uruk’s population, and today Anuradhapura is one of the world’s oldest continuously inhabited cities and still cares for a tree planted over 2,000 years ago.This tale of two ancient cities still rings true today. We may think nature is unconnected to our cities. But trees have always been a crucial part of flourishing urban spaces. At their core lies an impressive biotechnology. A mature, healthy tree can have a few hundred thousand leaves, each an instrument of photosynthesis. These porous leaves purify the air by trapping carbon and other pollutants, making them essential in the fight against climate change. In addition, trees act like a natural sponge, absorbing stormwater runoff and releasing it back into the atmosphere. The webs of their roots protect against mudslides while allowing soil to retain water and filter out toxins. Roots help prevent floods while reducing the need for storm drains and water treatment plants. “In some Native languages,” the ecologist Robin Wall Kimmerer has written, “the term for plants translates to ‘those who take care of us.’”