Green Walls To Cut Pollution In Cities

Apr 4th, 2013 | By | Category: Adaptation Ideas, Global Warming, Green House Gas Emissions, In Office, Lessons, Public Places, RESOURCES, Website-eNews Portal

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Adaptation Ideas’ is a new series of Climate Himalaya. Here we will be showcasing a number of simple, practical and innovative ideas those could be adopted by individuals, communities and organizations for various environment friendly adaptive practices at home, offices and in public places. The purpose of this ongoing series is to disseminate and communicate available practices, ideas and innovation for a better living planet ‘earth’. We collect these practices and ideas from various sources, and duly recognize and mention them in respective post.

How Green Walls Work

Illustration by Jason Treat, National Geographic. Source: Patrick Blanc

Many living wall systems also have built-in irrigation systems in which water is harvested at the bottom of the wall and recirculated back to the top, as seen above.

The types of plants on green walls differ, but can include grasses, vines, and other climbing plants—all of which must have strong root structures, Green Roofs for Healthy Cities’ Paul Erlichman said. (Test your environmental knowledge.)

Green Gold

Photograph by L. Wheatley, Garden Picture Library/Getty Images

A vertical garden (pictured) won the gold medal in the 2011 Chelsea Flower Show in London.

Each year Green Roofs for Healthy Cities issues the Green Roof & Wall Awards of Excellence. The 2013 winners will be announced in October at CitiesAlive: 11th Annual Green Roof and Wall Conference in San Francisco.

According to the organization’s website, green walls may improve your mood as well as your health. (Read about cities as solutions.)

“Studies have shown that visual access to natural settings leads to increased job satisfaction and productivity … and post-operative recovery rates in medical facilities,” the website says.

Against the Wall

Photograph by Carol Sharp, Eye Ubiquitous/Corbis

The ability of green walls, such as this one at the Musée du Quai Branly in Paris, to cool street canyons is especially key in the summertime, Thomas Pugh noted.

“If you have a surface covered in plants,” he said, “when the sun’s heat hits them, instead of just warming up they send a lot of energy back into the atmosphere as water vapor. Whereas a concrete wall would heat up and send [the heat] back into the canyon.” (Learn more about Earth’s atmosphere.)

Colorful Tableau

Photograph by Franck Guiziou, Images

A green wall creates a colorful tableau in Copenhagen‘s Kongens Nytorv (Royal Square).

The European Union sets standards for air pollution and imposes fines if levels within a country exceed those levels, noted study leader Thomas Pugh.

London and some cities in Western European countries in particular have had trouble keeping air pollution in check—making green walls a possible solution. (Also see “Pictures: London Leaps Hurdles in Green Olympic Games Bid.”)

Going Green

Photograph by Sandra Raccanello, Grand Tour/Corbis

In Madrid, plants turn a wall in the Paseo del Prada bright green.

Green walls are particularly useful in reducing pollution in street canyons, which are “a particular kind of oddity in that they tend to trap air within them, while over the city as a whole the air circulates freely,” Thomas Pugh noted. (Take a pollution quiz.)

Because a green wall’s vegetation is working with a much smaller volume of air in a street canyon, he added, it’s more effective at absorbing or trapping the pollutants than if it was tackling a whole mass of air above the city.

However, Pugh cautioned, “we need more research to understand just how effective green walls can really be in real locations.”

Vertical Garden

Photograph from UIG/View Pictures/Getty Images

Living walls can be indoors or outdoors, such as this one blooming on the Citi Data Centre in Frankfurt, Germany.

“Vertical gardens,” as they’re sometimes called, can visually enhance an otherwise forgotten space, noted Paul Erlichman of the Toronto-based group Green Roofs for Healthy Cities.

“Walls are the more underutilized spaces in our urban areas,” he added. (See National Geographic pictures of green roofs.)

There are three types of green walls: Living walls, green facades, and retaining living walls, he said.

In green facades, vines and climbing plants or cascading ground covers grow into supporting structures, according to the Green Roofs for Healthy Cities website.

Living walls are composed of pre-vegetated panels, modules, planted blankets, or bags that are affixed to a structural wall or free-standing frame. Finally, retaining living walls are engineered living structures designed to stabilize a slope.

Living Wall

Photograph by Bertrand Garbel, Images

A living wall bursts with vegetation at Paris‘s Musée du Quai Branly—a type of green wall that’s catching on in some big cities.

These vegetated surfaces don’t just look pretty. They have other benefits as well, including cooling city blocks, reducing loud noises, and improving a building’s energy efficiency. (See a complete list of green wall benefits.)

What’s more, a recent modeling study shows that green walls can potentially reduce large amounts of air pollution in what’s called a “street canyon,” or the corridor between tall buildings.

For the study, Thomas Pugh, a biogeochemist at the Karlsruhe Institute of Technology in Germany, and his colleagues created a computer model of a green wall with generic vegetation in a Western European city. Then they recorded chemical reactions based on a variety of factors, such as wind speed and building placement.

The simulation revealed a clear pattern: A green wall in a street canyon trapped or absorbed large amounts of nitrogen dioxide and particulate matter—both pollutants harmful to people, said Pugh. (Related: “Pictures: 10 Green-Tech City Solutions for Beating the Heat.”)

Compared with reducing emissions from cars, little attention has been focused on how to trap or take up more of the pollutants, added Pugh, whose study was published last year in the journal Environmental Science & Technology.

That’s why the green-wall study is “putting forward an alternative solution that might allow [governments] to improve air quality in these problem hot spots,” he said.

—Christine Dell’Amore

From: National Geographic  Source Link>>


Started in year 2010, ‘Climate Himalaya’ initiative has been working on Mountains and Climate linked issues in the Himalayan region of South Asia. In the last five years this knowledge sharing portal has become one of the important references for the governments, research institutions, civil society groups and international agencies, those have work and interest in the Himalayas. The Climate Himalaya team innovates on knowledge sharing, capacity building and climatic adaptation aspects in its focus countries like Bhutan, India, Nepal and Pakistan. Climate Himalaya’s thematic areas of work are mountain ecosystem, water, forest and livelihood. Read>>

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