21st century cities face environmental challenges of unprecedented magnitude. Urban sprawl, air pollution and rising temperatures due to the urban heat island effect are just some of the problems that threaten the quality of life of city inhabitants. Given this context, an architectural solution has emerged that combines functionality and sustainability: vertical forests, structures that turn skyscrapers into green lungs for cities.
The trend has been gaining worldwide momentum ever since Italian architect Stefano Boeri revolutionised urban design with his ‘Bosco Verticale’ project in Milan. But what exactly are these vegetation-covered skyscrapers, and how are they changing the urban and environmental landscape?
An idea that became a trend: what are vertical forests?
Vertical forests are buildings designed to house a wide variety of plants on their facades and terraces, creating a vertical ecosystem in the middle of the city. At first glance, they are a fusion of architecture and nature, but their purpose transcends aesthetics.
These buildings aim to reduce the environmental impact of cities and contribute to public health by regulating the local climate. The result: improved air quality and increased biodiversity.
The world’s first vertical forest, the ‘Bosco Verticale’, was inaugurated in 2014 in Milan. This project is made up of two residential towers and is home to more than 900 trees, 5,000 shrubs and 11,000 perennial plants. More than 2,000 plant species cover its facades.
As a result, it became a real forest in the heart of the Italian metropolis. Since then, the concept has been replicated in cities such as Singapore, Paris, Shanghai and São Paulo, demonstrating that the idea is adaptable to different climatic and cultural contexts.
The urban heat island effect: a solution to urban overheating
One of the most serious problems facing modern cities is the urban heat island effect. The term refers to artificial surfaces such as asphalt and concrete that absorb and retain heat, significantly raising local temperatures.
This phenomenon, at the same time, increases the energy demand for cooling buildings, indirectly contributing to the emission of greenhouse gases.
This is why vertical forests are presented as an innovative solution. The vegetation covering these structures acts as a natural barrier, reducing the amount of heat absorbed by buildings. In addition, the plants release moisture through transpiration, which helps to cool the surrounding air and improve the urban microclimate.
A recent study in Singapore showed that green facades can reduce surface temperatures by up to 5°C, a significant effect in hot and humid climates. This type of construction not only benefits the residents of the building, but also the surrounding areas, creating a network of cooler spaces in the city.
A natural filter for air pollution
Air pollution is another challenge facing cities. According to the World Health Organisation (WHO), more than 90% of the world’s urban population breathes polluted air, contributing to millions of premature deaths each year.
Vertical forests play a crucial role in improving air quality. During photosynthesis, plants absorb carbon dioxide and release oxygen, reducing carbon dioxide levels in the environment. In addition, the leaves and branches of trees trap pollutants such as dust, soot and heavy metals, acting as a natural filter.
As in the case of the ‘Bosco Verticale’, it is estimated that the plants on its facades absorb more than 20,000 kg of carbon dioxide per year. This impact may seem small compared to overall needs, but when combined with other urban strategies, it can make a significant difference.
A haven for biodiversity in cities
Mass urbanisation has had a devastating impact on biodiversity, displacing numerous species of flora and fauna. However, vertical forests are changing this dynamic by providing habitat for birds, insects and small mammals in the midst of urban environments.
In Milan’s ‘Bosco Verticale’, more than 1,600 species of birds and insects have been recorded using the plants as a refuge and food source. This integration of nature and urbanism not only benefits the ecosystem, but also has a positive impact on the city’s inhabitants, allowing them to reconnect with nature.
Other projects, such as One Central Park in Sydney, have taken a similar approach, incorporating specific irrigation and nutrient systems to maintain plant health and attract native species. These examples demonstrate that it is possible to combine urban development with biodiversity conservation.
Challenges and limitations of vertical forests
While vertical forests present numerous benefits, they also face significant challenges. One of the main obstacles is the high cost of construction and maintenance. Incorporating automated irrigation systems, selecting suitable plants and hiring landscaping specialists can add considerably to a project’s budget. For example, the Bosco Verticale was carried out with a budget of 65 million euros.
In addition, extreme climatic conditions can hinder the success of these structures in certain regions. In places with dry climates or strong winds, additional measures need to be implemented to ensure the survival of the plants.
On the other hand, some critics argue that vertical forests are a superficial solution that does not address the root causes of environmental problems, such as dependence on fossil fuels or the lack of green spaces accessible to all citizens. However, many urban planners defend these initiatives as a step in the right direction towards a more sustainable development model.
The future of cities: from concrete jungles to green oases
With climate change and urbanisation becoming increasingly urgent challenges, vertical forests represent a hopeful vision for the future. These structures not only transform the appearance of cities, but also offer practical solutions to critical environmental problems such as extreme heat, air pollution and biodiversity loss.
Though neither the only solution nor perfect, vertical forests are a tangible example of how architectural innovation can contribute to human and environmental well-being. As more cities adopt this approach, we will be closer to an urban model where nature is not a luxury, but an integral part of everyday life.
On the skyline of the cities of the future, breathing skyscrapers are a reminder that even in the most artificial environments, nature can find a place to flourish.
