Buildings covered in trees offer glimpse of future urban living

The major financial center of Milan boasts a number of tall buildings, many of which function as office space for firms like UniCredit and Allianz. 

While the city may be the corporate hub of Italy, it is also home to the Bosco Verticale, or Vertical Forest, a residential development of two visually striking towers that stand 80 and 112 meters high.

Located in the Porta Nuova area of Milan, the clue to what makes the Bosco Verticale scheme unique is in the name: its exterior is covered in plants and trees.

“We have here 21,000 plants, basically,” Stefano Boeri, the architect behind the design, told CNBC’s “Sustainable Energy.”

“It’s 200, 250 trees, 4,500 shrubs of different size and 15,000 plants of different dimensions and nature,” he added.

“It’s the equivalent of three hectares — 30,000 square meters — of … forest (on) … a very small surface of an urban center, of a super dense urban environment.”

Completed in 2014, a number of firms, including Arup Italia, were involved in the project’s development.

According to Boeri’s architecture practice, Stefano Boeri Architetti, the buildings’ “green curtain” can generate oxygen, regulate humidity and absorb carbon dioxide and microparticles.

The building has also attracted wildlife. “It is a very complex ecosystem of humans, plants, insects, birds,” Boeri said. “We have more than 20 species of birds that are nesting.”

While authorities in Milan recently announced a target of planting 3 million trees by the year 2030, the idea of greening cities with trees and plants is not new. From New York to London and Paris to Tokyo, parks have long been used to provide city dwellers with fresh air, space to exercise and a place to relax and unwind.

“To improve the quality of life in the city of Milan we need more forest, more trees in the city, outside the city,” Damiano di Simine, scientific co-ordinator at Legambiente, an environmental organization, told CNBC.

“We need to build, now, (a) green belt all around Milan and also within the city … to have more fresh air, to remove pollution,” he added.

The drive to increase the amount of green space people can access has resulted in a number of innovative, transformative projects in cities around the world.

These include New York City’s High Line, which converted an elevated rail line into a public park. A similar scheme is the Cheonggyecheon Restoration Project in Seoul, South Korea, which saw an elevated highway demolished and an underground waterway restored to create a green, pedestrian-friendly corridor.  

While the goal of increasing the number of trees in cities is laudable, there are several factors that need to be considered before embarking on mass plantings.

“I think it’s very important that trees are given space,” Cecil Konijnendijk, from the University of British Columbia’s Faculty of Forestry, told CNBC.

“We know that soil — what we call soil volume — is really important, so the trees have to have space underground, maybe even more so than over ground,” he added.

“And then of course trees will have to have time to develop, so you won’t have instant trees. You’ll have to take the time to make sure they grow up and then they provide the benefits that we want to get from them.”