Gardens in the sky:The rise of green urban architecture

Getting back to some natural vegetation, even in urban settings.  You are also seeing skyscrapers host major gardens on their roofs and are quickly adding solar to their panes and panes of glass. 

Gardens in the sky: The rise of green urban architecture

By Matthew Knight

 Story highlights

• Residential tower incorporates 800 trees
• "Vertical Forest" an alternative to city sprawl
• Green roofs increasingly common in cities

(CNN)With its balconies bursting with trees and shrubs, the "Bosco Verticale," or "Vertical Forest" is giving rise to an entirely new take on the traditional idea of the urban jungle. 

As city dwellers feel the squeeze on their living space and recreational areas, the twin residential towers in Milan, Italy offer up a refreshing vision of how urban skylines might look in the future.

Designed by Stefano Boeri architects, the towers, which rise to heights of 116 and 76 meters, contain more than 800 trees and 14,000 plants housed on steel-reinforced balconies. 

The project was conceived as an alternative to urban sprawl, a phenomena prevalent in cities around the world which not only compromises communal green space but can also negatively impact the health and safety of citizens, according to research published in 2014 by Smart Growth America.

"Biodiversity is one of the most important challenges in our urban environment," Stefano Boeri says.

"The Bosco Verticale hosts more than 100 species of trees and plants but it also has started to host 20 different species of birds."

Along with being festooned with flora and fauna, the development has been decorated with awards, winning two prestigious architectural prizes including the 2015 Best Tall Building Worldwide, chosen by the U.S.-based Council on Tall Buildings and Urban Habitat. 

Boeri and his team have their sights set on Switzerland next -- the Milan-based architects recently won a competition to erect a similar skyscraper in Lausanne -- the 36-story La Tour des Cedres takes its name from the cedar trees that will adorn the 117-meter high tower.

Switzerland has been a leader in incorporating ecological aspects to its urban infrastructure since the 1970s with an emphasis on green roofs where vegetation is planted helping foster habitats for wildlife.

The city of Basel boasts the largest area of green roofs per capita anywhere in the world and similar schemes have taken root across the continent.

In Stuttgart, around a quarter of all flat roofs are green while in London 1.3 million square-feet of roofs have green coverage, according to livingroofs.org.

"This a trend that's going on across Europe," says Jonatan Malmberg from the Scandinavian Green Roof Institute and manager of the Augustenborg Botanical Roof Garden — the world's first botanical roof garden in Malmo, Sweden.The flowers and shrubs planted on the roofs attract a range of birds and insects."I think green roofs also bring a great deal of aesthetic value for the people with balconies and windows facing them," says Jonatan Malmberg, head of projects and development at the Scandinavian Green Roof Institute. 

"Urban ecology is very cool, I think ... Personally I think green roofs also bring a great deal of aesthetic value for the people with balconies and windows facing them.

The march of green roofs seems set to continue ushering in a new, more ecologically orientated sprawl while for Boeri it's also onwards and upwards with a bold new project planned for Shijiazhuang, China.

"The challenge that we have accepted is to design the prototype of a real forest city, which reflects and multiplies the prototype of the Vertical Forest," he explains.

"A small vertical town of public residences and private buildings, offices, laboratories, museums, schools, completely enveloped by millions of leaves of plants, trees and lawns."

For green highrises, the sky, it seems, is the limit.