Urban populations are increasing, but building sites are finite. The concept of vertical cities has risen to the foreground in response to this conundrum.
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The catchy phrase refers to building upwards, including the various amenities and structures necessary for modern city life in one sky-high building. Of course, building upwards is no new phenomenon, but the tall buildings of the past are being torn down to make space for new, much taller buildings today.
Meeting the Challenges of Urbanization
Building upwards has been touted as a response to the challenge of urban space shortages. In some of the world’s largest global cities, building higher buildings is already a suitable response to space constraints in core districts.
In the next few years, we will see more projects stacking elements of the city on top of each other. In part, this will be driven by an increase in the world’s urban population.
The world’s urban population grew rapidly from the middle of the last century until now. In 1950, 751 million people lived in cities around the world. There were 4.2 billion people in cities by 2018.
Cities today include 55% of the world’s total human population, and by 2050 this proportion is forecast to increase to 68%. The increasing proportion of urban populations will accompany a few more decades of global population growth, according to forecasters. This will result in another 2.5 billion people moving into cities by 2050, bringing the total to 6.7 billion.
The rate of urbanization will not be consistent around the world. Researchers predict that 90% of the extra 2.5 billion people moving into cities in the next three decades will be in the continents of Africa and Asia.
In the next ten years, there will likely be another ten megacities to bring the worldwide number to 43. Megacities have over 10 million human inhabitants each and are more prevalent in the global south. Currently, around one-eighth of the human population lives in one of the 33 megacities around the world.
The fastest-growing cities in the world actually have fewer than 1 million inhabitants, and most of them are in Asia and Africa. Almost half of the world’s population live in settlements of 500,000 people or fewer.
Vertical infrastructure can answer the challenges of space limitation in growing megacities, especially in core districts and on brownfield sites. As these cities continue to grow into the second half of this century, restraining their total footprint will be necessary to minimize their impacts on the surrounding environment.
Vertical farms – multiple stories of hydroponic greenhouses in a large-scale, highly automated food factory – have been proposed and prototyped as a way to produce more food for the growing population, while recognizing the finite nature of available land.
Growing Up: How Vertical Farming Works
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Putting farms into buildings as a kind of vertical food infrastructure makes producing food compatible with the space limitations of the urban environment. The urban and rural economies have for millennia been incompatible with each other, precisely because of the space limitations that cities impose.
But introducing vertical farms to growing cities can remove the intrinsic environmental costs of separating food production from consumption. Transportation bears a significant brunt of the environmental costs of the food industry, bringing the food to the consumer all but eliminates it.
Bringing people closer to the means of the production of their food may also help to democratize it. Communities in cities can embrace vertical farming to take control of their own food supply, no longer having to rely on the creaking infrastructure of global commerce to bring them sustenance from around the world.
Are Vertical Cities More Sustainable?
The main sustainability benefit touted by proponents of vertical cities is their reduced land use. Indeed, the massive rewilding effort that many argue is needed to avoid a climate catastrophe will not be possible with a growing population that spreads further and further into new suburban settlements built on virgin ground.
As long as the embodied carbon of vertical infrastructure projects is not excessive – this may be achievable through sustainable materials and efficient engineering and design – they can provide sustainability benefits beyond their reduced footprint.
Providing heating, energy, air filtering, water, waste, and information technology services to one large building may be more efficient than providing it to multiple smaller buildings discreetly (although gravity remains a challenge for the highest concepts).
But, with the construction sector responsible for nearly 40% of global CO2 emissions related to energy use, whether or not to build in the first place is the most significant decision affecting any building project’s sustainability credentials.
Some industry experts have started to consider avoided carbon as well as embodied carbon as a metric for sustainability in construction. This would place a reduced carbon value on decisions that avoid using energy and resources (that could potentially be tied to carbon credits and other economic controls that could be introduced to incentivize more sustainable global development).
In a similar twist, efficiency in systems and design is beginning to take second place to sufficiency: the idea that new projects must demonstrate their value in terms of necessity, non-duplication, and a serious look at alternatives to new construction including retrofitting older buildings.
References and Further Reading
68% of the world population projected to live in urban areas by 2050, says UN. (2018) UN. Available at: https://www.un.org/development/desa/en/news/population/2018-revision-of-world-urbanization-prospects.html.
Alter, L. (2021). Instead of Asking How We Build, We Should Be Asking Why. Treehugger.com. Available at: https://www.treehugger.com/instead-of-asking-how-we-build-we-should-ask-why-5207459.
Bailey, S. (2021). Architecture Meets Agriculture in the Jian Mu Tower. AZO Build. Available at: https://www.azobuild.com/article.aspx?ArticleID=8433.
Franklin, P. (2018). The false promise of the vertical city. UnHerd. Available at: https://unherd.com/2018/07/false-promise-vertical-city/.
Keegan, M. (2019). Which is the world's most vertical city? The Guardian. Available at: https://www.theguardian.com/cities/2019/jul/16/which-is-the-worlds-most-vertical-city.
Neill, P. (2020). Construction industry accounts for 38% of CO2 emissions. Environment Journal. Available at: https://environmentjournal.online/articles/emissions-from-the-construction-industry-reach-highest-levels/.
Robinson, M. (2016). Vertical cities could be the future of architecture. Business Insider. Available at: https://www.businessinsider.com/vertical-cities-future-of-architecture-2016-4?r=US&IR=T.
Roxburgh, H. (2019). Is Chongqing's 'horizontal skyscraper' the answer to overcrowded cities?The Guardian. Available at: https://www.theguardian.com/cities/2018/jun/04/is-chongqing-china-horizontal-skyscraper-the-answer-to-overcrowded-cities-raffles.
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