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Cities are considered to be the number one threat to our environments with 2.5 billion people estimated to live in cities by 2050.1 More than 80% of global GDP is generated in cities2 and at the same time 75% of total emissions also come from cities.3 It is estimated that 43 megacities (cities with populations exceeding 10 million people) will exist by 20304 with 38 of 100 new cities located in Africa by 2100.5 However, this progress has a downside if we don't take action to prevent potential negative impacts. It's been estimated that over 800 species worldwide are threatened by urban expansion.6 In light of this, there's a pressing need for significant measures to ensure that as urban expansion continues, nature and its interconnected ecosystems are conserved and nurtured to thrive alongside human development. Urban expansion, and in particular, the building sector, is closely linked to providing shelter and protection for city residents. Given this connection, the sector plays a substantial role in shifting the paradigm from an all-grey concept to a grey+green concept. This entails integrating nature-based solutions (NbS) into buildings to enhance their life-span efficiency and promote the health well-being of both people and the environment. One such integrated design concept that has gained global recognition is the Bosco Verticale (Vertical Forest) developed by Italian Architect Stefano Boeri and his team.
It is estimated that 43 megacities (cities with populations exceeding 10 million people) will exist by 20304 with 38 of 100 new cities located in Africa by 2100.5
This pioneering building design completed in 2014 combines the knowledge of architecture and landscape ecology to create a symbiotic living space that benefits people and the planet’s natural ecosystem through the services it provides like reducing urban heat island (UHI) effect caused by the heat absorbed and released from all-grey type buildings and infrastructures.
Bosco Verticale is made of two residential skyscrapers (112 and 80 m in height respectively) with facades covered with the leaves of 800 trees (each measuring 3, 6 or 9m), 5000 shrubs and 15,000 perennials and/or ground covering plants. The plants on the facades together occupy an equivalent space of about 3 ha (i.e. ~30,000 m2 ) of woodland and undergrowth concentrated into just 3,000 m2 of urban space that absorbs ~19 tCO2/year., 7,8 The green façades were designed to effectively promote biodiversity with about 60 varieties of trees and 94 varieties of plants providing a favourable habitat for approximately 1,600 birds and butterflies. To safeguard the vegetation from pests through natural means, we released 1,200 ladybirds in the building's planters. This iconic structure shields residents from noise pollution and filters air pollutants, such as fine particulate matter (PM), primarily originating from vehicles. Additionally, its energy consumption is significantly reduced thanks to advanced insulation technology, which insulates against external temperatures and provides effective shading. As a result, the building remains cooler in summer (with an approximate -3°C temperature reduction) and warmer in winter, reducing the necessity for active cooling and heating within the internal spaces. 9 The yearly reduction in energy consumption is estimated to be about 7.5%.10 A study conducted on this specific building shows that vertical forests can positively influence the daily experiences of urban landscapes. They are believed to offer relief in cities, especially as urban areas worldwide become increasingly crowded, polluted, and hectic. Vertical forests also have the potential to evolve into restorative environments with therapeutic qualities. 11
In an interview with TLmag - a Belgian and bilingual cultural magazine, this is what Boeri said; “I personally believe that we have to change in terms of how we deal with the concept of nature. Nature is not something that lives outside, a kind of autonomous sphere from our lives… We have to experiment with a totally different proximity with [it]… We have to imagine a kind of double simultaneous movement: one is the movement of the citizens in the direction of the forest, because the forest needs our help…, and the second is the movement of trees in the direction of the city”.12 Unlike garden cities, the objective of the vertical forest is not to move people to the countryside, but rather to invite nature directly into city homes – maintaining densities that help limit urban sprawl.13
The vertical forest brings both urban and building-scale benefits. On the urban scale, it includes the reduction of the Urban Heat Island (UHI) effect and temperature mitigation, carbon sequestration, improvement in air and dust quality, absorption of pollutants, creation of biodiversity and natural habitats, and enhanced aesthetic appeal. On the building scale, it offers benefits such as improved health and energy efficiency, enhanced internal air quality through filtration and oxygenation, noise reduction, and agricultural benefits.14
After the Bosco Verticale, Milan was completed, other similar projects inspired by this concept have and continue to emerge around the world like the Trudo Vertical Forest Eindhoven, Netherlands, Vertical Forest Tirana, Albania, Easyhome Vertical Forest Huanggang, China, Bosco Verticale Dubai, UAE, etc. As awareness and knowledge about the necessity to reduce the building sector's embodied life cycle carbon emissions15 continue to grow, it's reasonable to expect that sustainable building concepts will keep evolving and improving in the future.
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1UN, Department of Economic and Social Affairs (2018)
2WEF, (2022). BiodiverCities by 2030
3WEF, (2020). The Future of Nature and Business
4UN, (2018). Around 2.5 billion more people will be living in cities by 2050, projects new UN report
5Bearak, et al., (2021). How Africa will become the centre of the world’s urban future. Washington Post
6Yale School of the Environment (2022). Cities Can Be Part of the Solution in Sustaining Species
7Stefano Boeri Architetti (n.d). Vertical Forest Milan
8Alph (2020). Bosco Verticale: reshaping the future of tall tower design
9Alph (2020). Bosco Verticale: reshaping the future of tall tower design
10Impact One (2023). Catalyst - Bosco Dubai presentation
11Visser (2019). Master Thesis: The Geography of Vertical Forests: Exploring the Green City
12Stefano Boeri Architetti (2020). Tlmag interview with stefano boeri
13Alph (2020). Bosco Verticale: reshaping the future of tall tower design
14Giacomello & Valagussa (2015). Vertical Greenery: Evaluating the High-Rise Vegetation of the Bosco Verticale, Milan…
15WorldGBC (2019). Bringing Embodied Carbon Upfront16
