Gian-Luca Kaufmann
As cities around the world keep growing at a rapid pace and global temperatures rise, sustainable city-planning is key. Vegetation and other forms of nature in urban areas have a lot of benefits, which are often not being fully taken advantage of.
Figure 1, www.axios.com
The future challenges of cities
Urbanization worldwide has been growing rapidly over the last few decades and there are no signs of slowing down any time soon. While countries like Belgium or Japan already have a very high level of urbanization, others like China are catching up at mind-boggling speeds. By 2050, more than two thirds of the world population are projected to live in urban areas, while today it is about half of the world population (UN, 2018). This does however come with a wide range of challenges. From public health, housing or education to safety and especially rising global temperatures, cities face huge challenges if they want to ensure a high level of life quality for the city residents (WEF, 2018). In this blog, I will focus on the effects of climate change on cities and what city planners can do to tackle them.
Figure 2, Urbanization over the last 500 years (https://ourworldindata.org/grapher/urbanization-last-500-years?time=earliest..latest)
The role of vegetation
Cities usually heat up more than its surrounding landscapes, which is due to the absorption of sun radiation by the surface material used in cities, which is often concrete. This can be a major problem when the hottest days of the year come around because these extreme temperatures can be a serious threat to the health of some people. Our bodies are simply don’t like extreme temperatures, which might lead to people not being able to leave their homes in the scorching heat. This may sound like we are about to enter a new era where living in cities will be less attractive. Fortunately, city-planners are not defenseless and they have a range of measures in their arsenal which can be used to lower temperatures in urban areas (Haider Taha, 2004).
Here, vegetation comes into play, because it can be a powerful tool for battling heat. Plants use solar radiation for photosynthesis, where carbon dioxide and water are converted into sugar and oxygen, which is already benefit in itself, because it contributes to better air quality. In this process however, plants also lose a lot of water through their stomata, which then evaporates. This process needs energy, which is used in the form of heat (lisbdnet, 2021) . And this is exactly the reason why plants directly cool the local microclimate. But there are a lot more benefits vegetation can provide in cities. For example better air quality, habitat for all kinds of organisms or places to meet and unwind for the city residents all contribute to a sustainable city (UN, FAO, 2016).
Vegetation can be used in all shapes and forms, such as single trees along the streets, planting vegetation on top of buildings or creating entire city parks. All of them have their own set of benefits besides the already explained cooling effect and also bring challenges with them, which is worth quickly looking into.
Single trees along streets in cities are useful because they provide shade and can look beautiful, but also because they absorb sound vibrations and therefore reduce noise in the city. Challenges can be the risk of falling branches and tree caring in general, but this can also generate jobs (Sara Bolduc, 2018)
Vegetation on top of buildings, which is called “green roofing” is something that may sound futuristic, but has already proven itself in various European countries. It can be used to promote biodiversity and urban agriculture, which has a lot of potential (Rufai Mohammed Ahmed, 2016).
Public green spaces such as parks are maybe the most beneficial form of vegetation in cities. Whether it is better environmental conditions in the city, a place for recreational activities, a way to escape the concrete desert or promoting biodiversity, urban green spaces clearly come with a lot of benefits (Europenow, 2021).
Current state and future
As of today, many cities around the world are starting to see the benefits of green spaces and vegetation in their cities. There are pioneers like Copenhagen in Denmark, that already use vegetation as a way to adapt to climate change as well as to promote an already high quality of life (European Comission, 2014).
However, while each city is at a different level of valuing nature as a tool in city-planning it is safe to say that there is still a lot of potential all around the world. It seems that cars, roads and concrete are still prioritized over green spaces in the majority of cities, despite clear indication that for a sustainable city, it should be the other way around.
While the present cities may not look very green yet, it is to hope that the already started trend continues to grow in the future. With the SDG’s as a global guide towards sustainability and a dedicated SDG to “sustainable cities and communities”, it is now up to local governments to implement the suggested measurements. Especially cities in Europe are already pushing towards a greener future. For example Barcelona has only recently decided to create “superblocks”, which join about nine normal house blocks together. Inside these superblocks, cars are highly restricted and the city planted trees and provided raised beds for residents to start planting food and flowers (Ronika Postaria, 2021). There are also less creative, but equally effective measurements such as the ones London has chosen, which is to dedicate 50% of its area to green spaces. To do that, the city plans to protect, enlarge and especially connect their already big amount of green spaces so that wildlife can thrive and move around more freely (Greater London Authority, 2018).
In conclusion, cities around the world find themselves at the beginning of a new era, which will most definitely look a lot greener. While the present may not look like more grey than green, there are a lot of indications to be hopeful. The challenges cities face today are huge and will not be easy to tackle but if we work together as a community, we can pave the road into a sustainable future for generations to come.
Sources
https://lisbdnet.com/what-is-the-process-of-evaporation-through-plant-leaves-called/
https://www.london.gov.uk/sites/default/files/london_environment_strategy_0.pdf
https://www.weforum.org/agenda/2018/10/the-5-biggest-challenges-cities-will-face-in-the-future/
https://www.sciencedirect.com/topics/engineering/urban-heat-island-effect
https://www.activesustainability.com/construction-and-urban-development/benefits-of-trees-in-cities/?_adin=11711554438
https://www.fao.org/zhc/detail-events/en/c/454543/
https://www.ijsrp.org/research-paper-0116/ijsrp-p4957.pdf
https://ec.europa.eu/environment/europeangreencapital/wp-content/uploads/2012/07/ENV-13-004_Copenhagen_EN_final_webres.pdf
https://www.researchgate.net/publication/327427119_The_benefits_of_trees_in_a_city_far_outweigh_their_costs