The Promise and Challenges of Vertical Forests

As land becomes scarce in urban areas, green space is slowly disappearing leaving cities as concrete jungles. One solution to mediating the health and environmental  problems associated with high density urban landscapes is green tall buidlings.

Since 2011, population growth in urban areas has outpaced that of suburbia for the first time in the post war era. As experts anticpate this migration to continue into the middle of the 21^st century, construction in major U.S. cities is booming. While tall buildings provide a solution for accomodating the influx into urban centers, they also affect the climate, air quality, and liviability of cities. To address these issues, the Italian architect Stefano Boeri has developed a vision for creating a biodiverse urban landscape. His BioMilan project is bringing his vision to life.

Bosco Verticale: A Vertical Urban Forest in Milan

Completed in October 2014, Boeri’s Bosco Verticale represents the first phase of the BioMilan project. Consisting of two residential towers, one 328 feet tall and the other measuring 249 feet in height, Bosco Verticale uses 900 trees, along with other plants, to act as natural air filters, noise barriers, as well as a means of improving energy efficiency. According to Boeri, the vertical urban forest he designed and developed is the equivalent of 22,695 square feet of terrestrial forest. Recycled grey water is used to irrigate the plants and trees.

Reintroducing dense vegetation into the urban landscape:

• Reduces urban heating effects,
• Removes CO₂ from the air while refreshing it by replenishing oxygen
• Provides a natural noise buffer
• Counteracts the negative effects of urban microclimates

Boeri’s plans include establishing urban farms, sustainable social housing, and using plants and trees to decontaminate former industrial sites.

Evaluating the Long Term Viability and Feasibility of Vertical Forests

The Council on Tall Buildings and Urban Habitats released a report evaluating the design Bosco Verticale. A review of the report provides insight into the extensive about of structural engineering work that went into the design and construction of the 26 and 18 story residential towers. For example, the designers not only had to take into account the support needed for the weight vegetation, but also the need account for wind effects posed by the tree canopy.

While the initial findings of the report are positive and give Boeri’s team credit for a number of innovations, the authors of the review found potential challenges. One is the long-term maintenance of the trees and plants, especially since they are in a foreign environment. For example, the trees at the upper levels of the structure exhibited signs of stress and required 20 percent more water than those at the lower levels. Another issue is how the public now and the future view and accept living with and in vertical forests.

What do you think of Bosco Verticale? Could this design work in U.S cities?