Vertical forests born from obsession
Air pollution is believed to cause three million deaths a year. And with the world’s population estimated by the United Nations to be growing at around 83 million people a year the race is on to find ways of purifying the air in the cities we live in.
With that in mind Italian architect Stefano Boeri’s come up a novel idea - vertical forests (Bosco Verticale). That essentially means residential high-rises packed with greenery, which can help cities build for density while improving air quality.
Boeri says the idea came from his obsession with trees and determination to make them an “essential component of architecture”, particularly as a weapon to combat climate change.
“I was in Dubai in 2007 and I watched this city growing in the middle of the desert, with more than 200 glass towers multiplying the effect of heat,” he recalls.
He wanted instead to create something that “as well as welcoming life, can contribute to reducing pollution, because trees absorb microparticles and CO2′′.
“Cities now produce about 75% of the CO2 present in the atmosphere. Bringing more trees into the city means fighting the enemy on the spot,” he said.
His first example of the Vertical Forest was built in Milan in 2014, two residential towers of 110 and 76m in height. Combined they house over 100 apartments, hosting nearly 500 medium and large trees, 300 small trees, 4500 shrubs and 15,000 plants.
On flat land each Vertical Forest equals, in amount of trees, an area of 20,000 sq metres of forest. In terms of urban densification it’s the equivalent of an area of a single family dwelling of nearly 75,000 sq metres.
Boeri says the vegetal system of the Vertical Forest contributes to the construction of a microclimate, produces humidity, absorbs CO2 and dust particles and produces oxygen.
“Vertical Forest increases biodiversity,” he says. “It helps to set up an urban ecosystem where a different kind of vegetation creates a vertical environment which can also be colonized by birds and insects and therefore becomes a magnet for and a symbol of the spontaneous re-colonisation of the city by vegetation and by animal life. The creation of a number of Vertical Forests in the city can set up a network of environmental corridors which will give life to the main parks in the city, bringing together the green space of avenues and gardens, and interweaving various spaces of spontaneous vegetation growth.
Boeri worked closely with botanists to create a nursery of trees trained to grow under specific conditions. His team faced many challenges, from how the balconies should be structured to take the weight of the plants, to how to secure the tree roots and what needed to go into the soil. They even carried out resistance tests at a hurricane centre in Miami.
Boeri has now created other Vertical Forest projects around the world. He’s written a book revealing the secrets and techniques behind it, which he hopes will encourage similar projects in developing cities.
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