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Article Architecture & Design

Vertical Forests by architect Stefano Boeri


Words by Sophie Wright

Illustrations by Stephanie F. Scholz

Photos by Stefano Boeri Architects & Paolo Rosselli

What if the skyscraper was more than a symbol of steely modernity? What if it actively played a part in improving city life, from the quality of the air we breathe to our fragile biodiversity? Turning grey to green, Italian architect Stefano Boeri’s ‘Vertical Forests’ reimagine the high-rise as a thriving ecosystem covered in trees and plants that help reduce air pollution. Boeri’s vision for an urban forest revolution is well on its way to becoming a reality: with two prototypes in production – in Milan and Lausanne – the firm’s next green tower is set to be finished in 2018 in Nanjing, China.

Swapping glass for greenery

The idea for Boeri’s vegetation-rich architectural experiment came about back in 2007 when he was in Dubai. Alarmed by the frenzied pace at which the surrounding desert was being filled with glass towers and skyscrapers, Boeri began to reflect on alternatives. “The excessive amount of glass on facades has a negative impact on the thermal effects in our cities,” he says. “So I began to think of how to go in a greener direction, building towers covered by plants. It was the need to introduce biodiversity in urban environments, through a strategy of densification of green surface and tree coverage inside cities and the demineralisation of building envelopes.” Envisioning nature as an integral part of his process, he created a model for a new form of sustainable residential building with ambitious aims to address a number of urban problems.

Illustration by Stephanie F. Scholz

A living façade

The first Vertical Forest consisted of two residential towers – one 110m high and the other 76m high – and was completed in central Milan in 2014, garnering praise for its symbiosis of architecture and nature. Created in close partnership with botanists, the towers boast 900 trees and over 20,000 plants from a diverse range of floral plants and shrubs. Each of the tower’s trees and plants was pre-cultivated to adapt to the conditions of the balcony and carefully positioned according to the sun exposure of the façade to encourage continual growth. The resulting vegetation helps to create an urban ecosystem that will improve biodiversity, becoming a friendly magnet for birds and insects. The more Vertical Forests created, the more these vertical environments can add to a city’s existing network of parks and other green spaces and make flora and fauna flourish.

Photo by Stefano Boeri Architects
Photo by Paolo Rosselli

Improving city life

In addition to contributing to the natural world, these lush green towers also address pressing manmade issues such as air pollution and urban sprawl. Through its vegetation, the Vertical Forest builds a microclimate that creates humidity, absorbs CO2 and dust particles and produces oxygen as well as keeping buildings cool in summer and warm in winter. Growing upwards has its benefits too. The equivalent of 7,000 square metres of forest and 50,000 square metres of family houses, each tower proposes an alternative to urban expansion by giving residents the opportunity to be in a green space in the middle of a densely populated city.

“The architect’s vision of the future is one where the ‘Forest City’ – filled with green buildings of all different heights – is the new norm.”
Illustration by Stephanie F. Scholz

An urban forest revolution

Describing the Vertical Forest as a “philosophy and living approach”, Boeri’s aspirations for the future of the project are global and all encompassing, as demonstrated by its latest incarnation: the Nanjing Green Towers. Covered in 1,100 trees and 2,500 plants and shrubs, the towers are set to provide 25 tonnes of CO2 absorption a year whilst producing approximately 60kg of oxygen per day. Between them, the towers will contain offices, a museum, a green architecture school, a private club, a Hyatt hotel as well as shops, a food market, restaurants, a conference hall and exhibition space. “One building is a drop in the bucket of pollution, but has a symbolic value that indicates a direction,” Boeri says. “The future which we are working for is to build cities completely made with greenery: buildings with different functions, as schools, hospitals, residential towers, office towers, covered by trees and plants.” The architect’s vision of the future is one where the ‘Forest City’ – filled with green buildings of all different heights – is the new norm.  

Photo by Stefano Boeri Architects