The Concrete Jungle Is Turning Green Again

Original publication by Stefan Al for on 13 April 2022. This story is adapted from Supertall: How the World’s Tallest Buildings are Reshaping Our Cities and Our Lives


Economic growth is often tied to environmental decline, but some cities are proving that doesn’t have to be the case.

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.’”

Trees even support each other collectively through mycorrhizae, fungal bridges that move carbohydrates between trees. This is “Earth’s natural internet,” Kimmerer has noted. “A kind of Robin Hood, they take from the rich and give to the poor so that all the trees arrive at the same carbon surplus at the same time … The trees all act as one because the fungi have connected them.”

Sadly, with urbanization, forests were cleared for agriculture, and poorer inhabitants felled urban trees for fuel. Thomas Jefferson, already suspicious of urban dwellers, denounced the trees’ removal as “a crime little short of murder.” “How I wished that I possessed the powers of a despot!” Jefferson once exclaimed at a dinner party. “I wish I was a despot that I might save the noble beautiful trees that are daily falling sacrificed to the cupidity of their owners, or the necessity of the poor. The unnecessary felling of a tree, perhaps the growth of centuries … pains me to an unspeakable degree.”

LITTLE BY LITTLE, green has made a comeback as cities sought to undo part of the damage done and restore their rivers. In Seoul, South Korea, an expressway and concrete paving had covered up a stream that once flowed through the city. In 2003, the mayor decided to take down the 40-year-old elevated expressway, restore the polluted stream, and create a park along its banks. The Cheonggyecheon stream is now a thriving recreation space. Fish, birds, and insects have returned, while the stream also does its part to alleviate the urban heat island effect, reducing the temperature of its adjacent areas by 6.5 degrees Fahrenheit (3.6°C).

Green projects like this are also undertaken to let nature do the work of pipes, pumps, and processing plants. Cities increasingly build bio-swales and rain gardens to replace stormwater pipes, and permeable pavers to edge out concrete sidewalks. Together, these measures work as a “green infrastructure” network to capture stormwater and filter water. All of this can help save costs on stormwater and paving systems. For instance, replacing Seattle’s streets with permeable pavement helped cut paving costs in half. Seattle also has a city ordinance requiring 30 percent of land parcels in commercial zones to be green and vegetated with planting. In addition, the city is providing bonuses for rainwater harvesting, larger trees, green walls, and green roofs. As these green initiatives help reduce stormwater runoff, they also save energy, since drinking water and wastewater systems, usually operated by local governments, can represent about a third of a municipality’s energy consumption in the United States.

Trees and vegetation are also moving to roofs, promoted by green roof ordinances. Zurich was one of the first cities to implement a law that mandates all flat roofs in the city, except for terraces, to be green surfaces. In Germany, about 14 percent of all roofs are greened. The city of Hamburg even enacted a policy to top 70 percent of all suitable roofs with vegetation.

This is a throwback to the green roofs of centuries past, like the Viking houses in Newfoundland. Until the 19th century, Norwegian log homes had been covered in turf, at times mixed with flowers and small trees, in order to provide the roof with thermal insulation. Today, green roofs are also praised for increasing the life span of roofs, since the vegetation protects roof membranes from ultraviolet radiation and temperature fluctuation.

Green roofs are increasingly home to vegetables. Urban agriculture, whether on roofs or in community gardens, has been making its way into cities as a way to reduce “food miles”—the energy wasted in shipping food from far away to your local grocery store. With fruit trees beginning to be part of cities, we have come full circle to our nomadic ancestors, whose lives centered around cultivating food, including trees known for their edible fruits.

Trees have come a long way from city walls to croquet allées, and from vegetated quads to building roofs. They are reaching full fruition in Singapore, the city that most embodies the potential of vertical green, with the most tree-covered skyscrapers.

ON MY FIRST visit to Singapore, it struck me how remarkably different the city looked from Hong Kong, despite its underlying similarities. Both are former British colonies with a comparably sized land area, and with similar population numbers and industries. Yet they could not be more different. In Hong Kong, closely spaced skyscrapers and underground infrastructure make it difficult for trees to grow. The city has narrow streets and crowded sidewalks, with skyscrapers blocking sunlight. With all the cables and pipes in its soil, very few trees survive in the city’s urban core. This contributes to the city’s dangerously poor air quality, which can cause bronchitis and diminished lung function.

In contrast to Hong Kong’s frenetic concrete jungle stands Singapore, a green oasis of calm. At the root of these two different destinies lies an opposing governing approach. Postcolonial Hong Kong was largely market-led, built by developers without too much of a grand plan. Singapore is top-down, led by the strong hand of a philosopher king, where nothing was left to chance. Both cities prospered, but in entirely different ways. Hong Kong became a public transit mecca, Singapore a city with a green thumb.

These differences can be traced back to 1965, in the aftermath of British colonial rule, when the Malaysian parliament voted unanimously to expel Singapore from the Federation of Malaysia. In this watershed moment, Singapore became the first nation-state to unwillingly gain independence. This left the small country, lacking natural resources, in a tough position. The new country’s prime minister, Lee Kuan Yew, had major challenges to solve. “I searched for some dramatic way to distinguish ourselves from the other Third World countries,” Lee said. “We struggled to find our feet.”

“To achieve First World standards in a Third World region, we set out to transform Singapore into a tropical garden city,” Lee decided. “Greening raised the morale of people and gave them pride in their surroundings.” In 1963, before independence, Lee had launched the first Tree Planting campaign. He planted the first tree himself, a Cratoxylum formosum, known for its light pink, cherry-blossom-like flowers. After independence, he strengthened these efforts. He launched the Garden City campaign and an annual Tree Planting Day to beautify Singapore. Lee chose the month of November, since this is when saplings need the least amount of water, at the cusp of the rainy season. In 1974, Singapore had 158,000 trees. Forty years later, it had 1.4 million.

In 1973, Lee set up the Garden City Action Committee and sent out green missions across the globe. “Our botanists brought back 8,000 different varieties and got some 2,000 to grow in Singapore.” Lee personally picked Vernonia elliptica—an unusual choice, since it has no flowers and, if unkempt, looks like a weed. But the city’s gardeners used the species widely to decorate the walls of unsightly buildings, bridges, and overpasses.

Lee, nicknamed “Chief Gardener,” enticed the leaders of his neighboring countries to go green as well. “I encouraged them, reminding them that they had a greater variety of trees and a similar favourable climate.” This would lead to a green race, with neighboring countries trying to “out-green and out-bloom” one another. “Greening was positive competition that benefited everyone—it was good for morale, for tourism, and for investors,” Lee assumed.

Greening also became about survival. Singapore is a country the size of a city. With about 6 million people, it has the same population as Denmark, but in an area only half the size of London. As a result, the nation is dependent on neighboring countries, like Malaysia, for things as basic as water. However, Lee knew that his neighbor could cut off Singapore’s lifeline, fresh water, during times of conflict. Malaysia’s president once said, “We could always bring pressure to bear on them by threatening to turn off the water.”

To avoid relying on other countries, Singapore needed to be self-sufficient within its own compact footprint. Having to capture rainwater, it could not afford to leave its rivers polluted, as so many other countries have done. Singapore, in the name of self-sufficiency, had no choice but to go green.

In 1963, Lee consolidated different entities to set up a national water agency. For 10 years, the agency toiled to clean up the rivers, which until then were an open sewer. Public officials relocated factories and farms and built water reservoirs, planning to collect and reclaim stormwater in the city. “By 1980, we were able to provide some 63 million gallons of water per day,” Lee stated, “about half of our daily water consumption then.”

Today, Singapore features a myriad of water reservoirs, rooftops, parks, roadways, and sidewalks to all capture water. Two-thirds of its surface is a water catchment area. An elaborate system of channels, tunnels, and pumps then moves the water to treatment plants, all controlled by microprocessors.

Parallel to greening Singapore, Lee wanted to get people to own flats. Homeowners, he assumed, would have a bigger sense of belonging than tenants. The city’s Housing & Development Board (HDB) would build low-cost housing that citizens were allowed to rent and then purchase with their pension funds. Today, 88 percent of all Singaporeans are homeowners, among the world’s highest home-ownership rates. It’s worth noting that the system deliberately disadvantages same-sex couples and excludes several hundred thousand migrant workers, who are living in crowded dormitories. With limited land supply and rapid population growth, Singapore had no choice but to build up. It needed to house everyone in skyscrapers. This transition to high-rise living did not come easily, especially for pig farmers, Lee noted. “Some were seen coaxing their pigs up the stairs!”

The groundwork of Singapore’s new green skyline was laid. As the state mandated green policies and high-rise buildings, it was only waiting for nature to intertwine with the skyscraper. Defying the negative stereotypes around public high-rise housing, the city’s skyscrapers became sleek, modern, and increasingly vegetated. In 2009, the HDB completed the Pinnacle@Duxton, the world’s tallest public housing project. It features seven 50-story towers interconnected with elevated landscaped gardens, allowing residents a daily jog among palm trees, 500 feet above the ground.

SINGAPORE PLANS TO use all this greenery to offset its fundamental fault. The city came at the cost of its tropical forest. Only 0.5 percent of the nation’s primary forests remain. Urbanization impacted the climate, with urban areas up to 9 degrees Fahrenheit warmer than rural areas. The city’s newly planted trees and green walls will help cool buildings, provide shade, and reduce outdoor temperatures. Hopefully, this will encourage people to walk or take a bus, instead of taking a climate-controlled cab.

But the question remains how sustainable Singapore’s network of more than 350 parks really is. The Gardens by the Bay, while iconic, is an artificial forest park—like a zoo for plants. Singapore has lost about half of all its animal species over the past two centuries. The same may happen to the rest of Southeast Asia by the end of this century.

Much of Singapore’s greenery cannot be eaten. The city-state produces less than 10 percent of its vegetables locally. Hence, it cannot rely on its own land to supply everyone with enough food. In an effort to rethink its food supply, it planned the Kranji Heritage Trail, which takes tourists on a path across the last remaining enclaves of local farming. However, skeptics consider urban land too expensive for agriculture.

Singapore is actively looking to solve this problem. Sky Greens, the world’s first commercial vertical farm, consists of 120 aluminum A-frames, each with 38 tiers of plants, floating in a pond of water that captures rainwater and grows fish. Each A-frame revolves vegetables, like a Ferris wheel, so the tomatoes and other produce get bathed in sufficient water and light. The vertical farm produces half a ton of fresh vegetables per day. With 6 million mouths to feed, the city will need to find space for several thousand more.

Singapore also faces an energy challenge to become truly sustainable. The Singapore economic miracle so far has worked because of air-conditioning, once singled out by Prime Minister Lee as one of two important factors to enable the city’s success, along with multicultural tolerance. “The first thing I did upon becoming prime minister was to install air conditioners in buildings where the civil service worked. This was key to public efficiency.” But air-conditioning is a major energy guzzler, accounting for 60 percent of all energy use by nonresidential buildings.

Still, Singapore has become a model for sustainable development worldwide. Cities wanting to adopt similar policies may find it difficult, though, since Singapore relies on strict enforcement. For instance, some elevators have been outfitted with urine detection devices to detect urine’s scent, close the doors, and call the police. For its draconian penalties on offenses such as spitting and chewing gum, author William Gibson, no stranger to dystopian visions of the future, once described the city as “Disneyland with the death penalty.”

Nevertheless, as carbon emissions are heating up our atmosphere and urbanization is disrupting our natural system, Singapore remains a test bed for a more sustainable urban future—one centered around the greenest skyscrapers.

Excerpted from Supertall: How the World’s Tallest Buildings Are Reshaping Our Cities and Our Lives, by Stefan Al. Copyright © 2022 by Stefan Al. Used with permission of the publisher, W. W. Norton & Company, Inc. All rights reserved.

Related Articles

Climate scientists are working with indigenous tribes

When the warm nights used to come each summer, Frank Ettawageshik would spend most of his time outdoors, sleeping outside, right o...

15 November • 8 min read

The young people taking 32 countries to court in an ‘unprecedented’ climate case

Six young people from areas of Portugal ravaged by wildfires and heatwaves went head-to-head with 32 European governments on Wedne...

09 October • 3 min read

A sinking community turns to oyster shells – and a tax – for safety

The terrain of southeast Louisiana has been drastically altered by the combination of hurricanes, sea-level rise, and the construc...

06 October • 6 min read

How a nuclear disaster turned Fukushima into a renewables leader

Following the 2011 triple disaster — and the subsequent cratering of support for nuclear energy — Fukushima Prefecture has pos...

05 October • 9 min read