Carbon Footprint – How Can Urban Landscapes Modulate Theirs?

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Does economic growth necessarily go hand-in-hand with environmental decline? Can cities reject this trajectory of an ever-increasing carbon footprint, and, instead, create urban landscapes that are (re)connected to nature?

What comes to mind when you think of a city? A concrete jungle. Closely spaced skyscrapers. A built environment that suffocates nature. Heavy industrial skies filled with smog. Murky trickling streams. Gray clouds from smokestacks. Or do you think of light glittering off walls of windows? A joie de vivre arising from the combined physicality and its inhabitants. Smartly constructed structures imbued with past values. Public gathering spaces. Economic opportunities. A global mélange of culture and place identity.

Whichever your vision is, cities need to transcend their reliance on stifling, toxic, deadly fossil fuels and suppression of the natural world. Instead, urban landscapes need to become sustainable within their own carbon footprint, and, to do so, they have to be aware of the expanse of their carbon legacy and then take specific and effective steps to shrink it.

Contemporary urbanization has dramatically changed our physical and social environments. Terms like urban sprawl, urban fringe, and suburbanization are common in relation to urbanization. We see it when we fly across vast stretches of formerly rural or natural landscapes — they’re now urban and industrial, easily identifiable by concurrent spatial patterns of architecture and accessibility to transportation routes.

Ancient Cities & Lessons (Sometimes) Learned

When trees were sacred, urban irrigation systems worked in conjunction with surrounding forests, capturing and respecting leaves’ and roots’ impressive biotechnology:

• purifying the air by trapping carbon and other pollutants
• absorbing stormwater runoff and releasing it back into the atmosphere
• drawing on massive root systems to protect against mudslides
• retaining water
• filtering out toxins

Why did the Vikings in Newfoundland cover their log homes with a variety of turf, flowers, and small trees? This green infrastructure provided thermal insulation without the kind of carbon footprint we see today.

Ancient cities that degraded their natural surroundings did so at their peril.

Then and now, trees are essential in the fight against climate change, as they reduce the need for storm drains and water treatment plants. So, too, are other natural sources. According to the American Association of Landscape Architects (AALA), green infrastructure describes a broad swatch of environment features in an urban setting: from parks to street trees and green roofs — really anything that helps absorb, delay, and treat stormwater, mitigate flooding, and alleviate pollution downstream. Bio-swales and rain gardens, for example, often  supplement existing, failing stormwater pipes.

Plus, urban greenery, according to the AALA, also improves mental health and well-being.

Other features of urban landscapes are necessary, too, to reduce cities’ carbon footprint, such as smart meters, efficient public transportation, energy efficient buildings, and clean energy sources.

Progress in Urban Landscapes

By 2050, two of every three people on Earth will live in a city. All is not lost for our many contemporary cities, though. Many cities are undergoing an environmental renaissance in attempts to restore natural systems of irrigation, water retention, and filtration.  By reconnecting with nature, cities are coming into their own.

When Seoul, South Korea uncovered a city stream and created a thriving recreation space, the effect on urban heat reduced temperatures of its adjacent areas by 6.5 degrees Fahrenheit (3.6°C). Green infrastructure also creates oxygen, sequesters carbon, and supports wildlife habitat.

Replacing Seattle’s streets with permeable pavement helped cut paving costs in half. Seattle also has a city ordinance requiring 30% 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.

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% of all roofs are greened. The city of Hamburg even enacted a policy to top 70% of all suitable roofs with vegetation.

A Sustainable Cities Case Study: Singapore

Singapore originally set out to be a tropical garden city. A Garden City campaign, annual Tree Planting Day, and Garden City Action Committee inspired neighboring countries in a “greening” competition that was not only good for morale, tourism, and investors but also about survival. Due to its dependency on neighboring countries like Malaysia for things as basic as water, Singapore needed to be self-sufficient within its own compact footprint.

Having to capture rainwater, it could not afford to leave its rivers polluted, so a national water agency came into being. Today, Singapore features all kinds 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.

Singapore’s green roofs serve as a shield from ultraviolet radiation and temperature fluctuations. They can grow vegetables and reduce agricultural transportation emissions. Those green roofs are important, as Singapore only produces about 10% of its own vegetables.

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. Of course, this is just a start: several thousand more vertical farms are needed for Singapore to become food independent.

So much has been done in Singapore to make it one of the world’s most sustainable urban landscapes. If you’d like to learn more about the greening of Singapore, read Supertall: How the World’s Tallest Buildings Are Reshaping Our Cities and Our Lives, by Stefan Al.

Final Thoughts about Urban Landscapes and Carbon Footprint

Have you ever been in a city on a warm day and felt as if the temperatures around you were higher than the areas just outside the city?  They are. That’s because a city’s roads, buildings, and other infrastructure absorb the sun’s energy, raising temperatures far above those in surrounding rural areas. Heavily industrialized areas that are devoid of vegetation reradiate heat, increasing their carbon footprint in multiple artificial ways: asphalt, HVAC units, cars, and tall buildings block winds, to name a few.

This “urban heat island effect” has been affected by climate change, so it’s increasingly difficult to keep vulnerable and rapidly growing populations safe during extreme heat events. The heat island effect is reduced when different city areas incorporate vegetation, which increases cooling. When plants photosynthesize, they release water vapor and cool the air.

With heat creating severe health situations for urban dwellers, urban landscapes can be soothed by developing more green spaces, adding reflective roofs and pavements, expanding bike lanes, showcasing green buildings, managing watersheds meticulously, and developing smart energy policies.

We can aspire to cities where people and nature both thrive.