Silvan Liechti
Designing sustainable cities should include ecological measures as a key goal. This blogpost aims at elaborating on the advantages and explains one of many measures to promote biodiversity in cities.
Division of humans and nature
Cities are often thought of as “the living space of humans”. It is where the division of “us” and almost all the other living beings happens. It seems like there is simply no space available for other things than the necessities solely of use to humans. Or is that so? Humans have been intertwined with flora and fauna since the beginning of their time. I find it ridiculous that we build our very living space without nature along our side. An urban planner might argue that we simply do not have the space anymore due to the settlement pressure. Other problems are the huge areas needed for agriculture and livestock breeding. There is obviously a need to discuss the future ways of how we build cities, which we might have to go about very differently than nowadays. But for now, let’s focus on how to optimize the existing cities. It is well known that nature is crucial to the physical and especially mental health of humans.
Sustainable cities are closely associated with words like inclusive, safe, resilient etc. Many of which I would instantly connect with nature. For example, the word “resilient” brings strong, robust ecosystems to my mind. Having attended the lectures regarding sustainable cities, of the course “The SDGs in Context” at ETH Zurich, I was all the more surprised when including nature was hardly on the agenda. As a student of Environmental Sciences, I could not believe that including ecological aspects was no major goal.
Including ecological aspects is not only desired, but also an obligation
Why we should integrate nature in our understanding of sustainable cities: The positive effects of nature on the human’s mental health are hard to quantify, and yet well known. Patients have shown faster healing, doctors order walks in the woods against stress symptoms, office productivity goes up when plants are placed in the room etc. Marselle et al. (2021) show a proof for my argument that biodiverse ecosystems can promote health and well-being in an urban environment. With the world’s population growing ever bigger and cities getting ever more crowded, more stress on the humans living there is inevitable. In order for cities to uphold high living standards, countermeasures must be taken. And promoting biodiversity in urban areas was proven to be effective.
Why we are obligated to promote biodiversity: Not only can our mental health benefit from promoting biodiversity, but it is also essential to humanity’s survival altogether. By the polluter-pays-principle I would argue that the polluters must conserve and restore biodiversity, because they are also the ones destroying it. Whether a person is a big burden to nature or not at all does not matter for my argument. There is one earth, and everyone should be invested in not overusing it. Due to the growing world population, more and bigger cities will be built and if this is not rightfully done, more biodiversity will be lost. Therefore, I see it as all our responsibility to care for biodiversity.
Two birds, one stone: The good news is that we can solve two problems at once. By implementing measures that promote biodiversity, we not only ensure our survival by maintaining a healthy ecosystem, we can also enhance our mental health at the same time. Taking measures in this area is promising as it seems to be a powerful lever.
An approach to network biodiversity in cities; roof greening public transport stops in Zurich
Implementing big changes is hard. Everyone’s interests have to be considered and as the saying goes “You can’t make everyone happy”. Topics like biodiversification are not easily measurable and therefore look like an investment without any immediate gains. Hence, it is hard to convince stakeholders like the canton to spend their budget on renaturation projects. Space is obviously another limiting factor in cities. Not going further with the brainstorming, we already got two major hurdles to overcome. Cities need a low-cost and space-efficient measure to jumpstart the biodiversification. Creative inventions are therefore needed to get the most nature out of the least space.
Küffer and Vega (2021) could demonstrate that also in dense urban settlement wild plants can thrive. Bigger patches of “green space” correlate with higher biodiversity. With space being a limiting factor, it is important to assess how big and how frequent these patches must occur. Over 75% of the investigated patches were smaller than 20m2. Even though species richness is higher for bigger patches, the small ones taken together still outweighed the bigger patches’ species richness because of their accumulated diversity. We can therefore say that it absolutely makes sense to implement small patches in the city as well. It does not have to be very big areas all at once. Spaces as small as 4m2 not further apart than 50 meters are sufficient to significantly alter the biodiversity of the interconnected land patches. Examples for patches are mowed meadows, a flower lawn and basically any other area with a diversity of plants on it.
Many possible options come to mind to green the city. Urban gardening, roof greening, more parks and many more. Measures of course must be specific to their location, thereby supporting its environment with what it needs most. One possible measure that I find promising and suitable for Zurich is roof greening of bus and tram stops. They pose convenient locations for roof greening because they are well distributed, they are not used for anything else, and it is relatively cheap because the infrastructure is already given. Fellow students and I studied possible locations where such patches could be installed. The idea was to start with an area where we could link bigger patches like forests and big meadows through smaller patches in between – to combine them into one big habitat again, so to say. We chose to promote a certain wild bee, Andrena schencki, because she is a local but endangered species. Bees are known to be essential to the environment, most of all because they are a key species to pollination. We chose the settlement area of Affoltern where many bus stops have roofs and are near to each other. They are the “bridge” to connect the three adjacent forests. The bus stop roofs are thought to be little oases for bees and other insects, so they don’t starve to death in the only jungle where food is rare – the urban jungle.
Conclusion
Integrating nature into our design of sustainable cities should be a key component. We have seen that it is not only beneficial for our mental health, but also necessary for humankind to survive. The world population will most probably grow much bigger and with it more natural habitats will be destroyed. We will have to find a way to integrate nature in our living space, otherwise we might destroy the very ecosystem that keeps us alive. Solutions are infinite and the start of the solution could be the roof greening.
Fig 1. Possible bus stop for roof greening in Affoltern ZH
References:
Marselle, M. R., Lindley, S. J., Cook, P. A., & Bonn, A. (2021). Biodiversity and Health in the Urban Environment. Current Environmental Health Reports, 8(2), 146–156. https://doi.org/10.1007/S40572-021-00313-9
Vega, K. A., & Küffer, C. (2021). Promoting wildflower biodiversity in dense and green cities: The important role of small vegetation patches. Urban Forestry and Urban Greening, 62. https://doi.org/10.1016/j.ufug.2021.127165
Kueffer, C., Vega, K. A., & Zurich, E. (n.d.). Förderung von Wildpflanzen in verdichteten Siedlungsräumen. The social-ecological impacts of invasive species View project. https://doi.org/10.1016/j
Andrena schencki. https://www.wildbienenwelt.de/Wildbienen-bestimmen/Wildbienen-Finder/article-6515631-190818/andrena-schencki-.html, (2022, April 12).
Morgan Phillips Taft. Bee is for Biodiversity. https://defenders.org/blog/2021/05/bee-biodiversity (2022, April 12).