Vertical Forests: Bringing nature back into cities
What is a Vertical Forest?
A vertical forest is a type of high-rise building designed to incorporate trees, shrubs, and other vegetation directly into the building’s structure. The concept was developed by architect Stefano Boeri as a way to reintroduce biodiversity into dense cities where green space is limited. Instead of traditional façades made only of glass or concrete, these buildings include planted balconies and terraces that allow trees and vegetation to grow vertically along the structure.
What is a Real Example of a Vertical Forest?
The most famous example is Bosco Verticale in Milan, completed in 2014. The project consists of two residential towers approximately 110 m and 76 m tall located in the Porta Nuova district.
The buildings host a large amount of vegetation integrated into their balconies, including:
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800 trees
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4,500 shrubs
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20,000 plants
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More than 100 plant species
All of this vegetation is concentrated on a building footprint of about 1,000 m², yet it provides the ecological equivalent of approximately 5 hectares of forested parkland if spread on the ground.
How Does a Vertical Forest Work?
The design of the building itself supports plant growth. The towers feature projecting balconies extending about three metres, which hold large planters where trees and shrubs can grow. The arrangement of balconies is carefully planned so that tree canopies have enough space to develop vertically across multiple floors.
Plant species are selected based on factors such as sunlight exposure, growth height, and local climate. For example, evergreen trees may be placed on sun-exposed façades while deciduous species are positioned on cooler sides of the building.
What Environmental Benefits Do Vertical Forests Provide?
Vertical forests can improve urban environmental conditions in several ways. The vegetation helps absorb carbon dioxide and fine particulate pollution, produce oxygen, and reduce noise pollution. The trees also create shade and release moisture through evapotranspiration, which helps regulate the building’s microclimate.
Studies of the Milan towers show that the vegetation can lower surrounding surface temperatures by up to 30 °C and reduce indoor temperatures by about 2–3 °C, helping decrease the need for air-conditioning.
Why Are Vertical Forests Important for Cities?
Vertical forests demonstrate how architecture can combine urban development with ecological restoration. By stacking vegetation vertically, cities can introduce large amounts of greenery without expanding into surrounding land. This approach increases biodiversity, improves air quality, and helps mitigate the urban heat island effect, making cities more resilient to climate change.
Why Is This Relevant to Gibraltar?
The concept of vertical forests may be particularly relevant to Gibraltar due to its limited land area of approximately 6.8 km² and highly urbanised environment. With little space available for new parks or large green areas, integrating vegetation into buildings could help increase urban greenery without requiring additional land.
Features such as planted balconies, green façades, and rooftop vegetation could help improve air quality, reduce urban heat, and provide habitat for wildlife within dense urban areas. While large towers like Bosco Verticale may not be directly applicable in Gibraltar, the underlying principle of incorporating vegetation into building design could still support more sustainable urban development.
References:
Stefano Boeri Architetti. Vertical Forest (Bosco Verticale).
Available at: https://www.stefanoboeriarchitetti.net/en/project/vertical-forest/
(Accessed: 26 March 2026).