Planting the Road to Greener Cities - by Marijke DeWulf
14 December 2020
In an age where 55% of the world’s population lives in urban areas, a number expected by the United Nations DESA to rise to 68% by 2050, it’s increasingly important to consider the effects of urban living on human well-being. Research suggests that living in a city can come with many possible health detriments, from psychological overstimulation to pollution-related respiratory illnesses. The solution to these problems, however, can be simple: urban green space. “Green space” is a term used to describe land that is at least partially covered in vegetation—shrubs, grasses, trees, flowers, and so on. Green spaces come in many forms, from a family’s backyard to untouched wilderness. When integrated into a city, these natural areas can have many benefits. By reducing pollution and improving inhabitants’ health, urban green space is a major component in helping keep cities clean, healthy, and environmentally sound.
Time after time, natural areas in cities have been shown to have incredible effects on the local atmosphere.
One of the most significant effects is pollution reduction. It’s common knowledge that plants intake carbon dioxide and release oxygen, but what’s less well-known is the extent to which this can happen. Researchers David Nowak and Gordon Heisler claim in their article, “Air Quality Effects of Urban Trees and Parks,” that “One acre of park tree cover will likely store, on average, around 40 tons of carbon and remove about 1.2 tons of carbon per year” (30). In combination, this is equivalent to just over four homes’ carbon emissions for one year. This may not seem like a significant amount, but in addition to the carbon reductions offered by the other components of green space (grass, shrubs, etc.), a considerable change can be made. It is also worth noting the other benefits that green space offers, such as heat reduction. In recent years, more and more research has been published regarding what is called the “urban heat island effect.” Urban heat islands are areas of disproportionate heat within a city caused by the vast expanses of pavement commonly found in urban settings. These areas function as heat traps, absorbing and retaining heat. However, areas of greenery can help prevent this from happening. The Environmental Protection Agency explains in their online article, “Reduce Urban Heat Island Effect,” that the flora found in parks and green roofs can deflect solar radiation, shade buildings and streets, and release moisture into the atmosphere, with an overall effect of lowering city temperatures. These ecological boosts are not only beneficial to the earth and environment at large, but also to city residents.
Green space plays an understated role in public health. With higher pollution concentrations, more background noise, and a simple lack of natural areas, living in a city can lead to various health problems, both physical and mental.
As mentioned before, green space reduces pollution and thus reduces pollution-related respiratory issues, but that’s far from all that it does. Green space can encourage exercise by providing a safe, cost-free, outdoor area for recreation. It can also provide psychological relief from city living. Cities tend to be loud and busy, which, over time, can overstimulate the human mind. However, green space buffers noise, not only mitigating noise levels across the city, but also creating quiet, solitary areas for mental respite. In fact, a 2019 study by university researchers Kristine Engemann et al. demonstrates a strong connection between childhood access to green space and mental health: their research shows that “Risk for subsequent mental illness for those who lived with the lowest level of green space during childhood was up to 55% higher across various disorders compared with those who lived with the highest level of green space” (1). That is, the more childhood exposure to green space, the less likely one is to develop an urbanization-related mental illness. There are many factors that determine an individual’s psychiatric profile—socioeconomic status and family genetics are two major ones—and different disorders seem to be connected to different factors. For example, substance abuse disorders are strongly connected to childhood socioeconomic status (Engemann et al. 2). However, many disorders were found to be most strongly connected to childhood green space levels: “mood disorder, single and recurrent depressive disorder, and neurotic, stress-related, and somatic disorder risk were mostly associated with [green space exposure]” (Engemann et al. 2). Additionally, Engemann et al. claimed, “the association with [green space exposure] was comparable in magnitude to or even higher than those of other known risk factors, including parents’ socioeconomic status, history of mental illness, and age” (3). There are many factors related to mental wellbeing that are difficult or even impossible to change. However, if something as simple and widely beneficial as green space has such a major impact on millions of people’s lives, it’s a worthwhile investment.
Incorporating natural areas into every city across the world may seem like an insurmountable challenge—even implementing these areas locally can seem daunting. After all, the required time, work, and money must be considered. However, these investments can pay off in the end: the U.S. Park Service states in “Green Roof Benefits” that “Over its estimated lifespan of 40 years a green roof would save about $200,000, of which, nearly two–thirds would come from reduced energy costs.” There are several reasons why this is. Green roofs absorb much less heat than their traditional counterparts, which leads to lower air cooling costs. Additionally, the soil required for green roofs acts as an insulator, reducing heating costs. Green spaces can also reduce city expenses with regards to stormwater runoff: “The Trust for Public Land noted Atlanta’s tree cover has saved more than $883 million by preventing the need for stormwater retention facilities” (qtd. in EPA, “Reducing Stormwater Costs” 7). Natural areas absorb water and reduce runoff. This can help prevent city drainage systems from being overwhelmed, thus preventing flooding. Although starting the process of making greener cities is difficult, it’s clear that the payoff is worth it.
It is important, however, to remember that ecological cities can’t be achieved only through individual green spaces, but rather through a city-wide effort. Many of the benefits that a park offers can be easily negated by an otherwise environmentally-unfriendly setting. A case study by Emma Salizzoni and Rocío Pérez-Campaña examines the Charca de Suárez, an urban wetland area along the Coast of Granada, Spain. Salizzoni and Pérez-Campaña highlight the importance of considering the surroundings of green space, as well as the areas themselves:
Surrounding urbanization could deeply affect factors such as water quality and ecological connectivity [the uninhibited movement of species across the Earth] and jeopardize the results which have been achieved. To preserve and enhance the current Charca landscape values, a landscape network approach should be put in place, considering the Charca as a node of a wider system of open areas, thus avoiding its ‘insularization’ [to become separated from one’s surroundings] (16).
Concentrated areas of vegetation are a valuable component of an environmentally-friendly city, but even then, green space is just one part of the solution. Ethical property zoning restrictions are important too—with improper land zoning, pollutants such as asphalt plants could be built in proximity to a major river. Carefully controlled carbon dioxide emissions are also necessary. These factors, along with others, work together: each one connects to and influences all the rest. Accordingly, every factor must be addressed in order to foster an environmentally sound city.
With so many pieces to be considered, creating more ecological cities is far from a simple endeavour. However, with numerous benefits to humans and the environment at large, it is simple to see why urban green space plays such an important role. Many cities have already taken steps in this direction: Richard Coniff, a National Magazine Award-winning writer, reports in “Urban Nature: How to Foster Biodiversity in World’s Cities” that “University of Virginia researchers recently announced the beginning of a Biophilic Cities Network devoted to integrating the natural world into urban life, with Singapore, Oslo, and Phoenix among the founding partners.” The Biophilic Cities Network is an organization committed to working with communities across the world to create and diversify green spaces in urban areas. It’s far from the only initiative of its kind—environmental concerns are gaining traction around the world. With increasingly compassionate and educated communities and individuals, the road to greener cities can be paved—or planted—in no time.
Conniff, Richard. “Urban Nature: How to Foster Biodiversity in World’s Cities.” Yale Environment 360, Yale School of the Environment, 2014, e360.yale.edu/features/urban_nature_how_to_foster_biodiversity_in_worlds_cities. Accessed 8 Nov. 2020.
Engemann, Kristine, et al. “Residential green space in childhood is associated with lower risk of psychiatric disorders from adolescence into adulthood.” Proceedings of the National Academy of Sciences, vol. 116, no. 11, Mar. 2019, pp. 5188-93. PNAS, doi:10.1073/pnas.1807504116.
“Green Roof Benefits.” U.S. National Park Service Technical Preservation Services, www.nps.gov/tps/sustainability/new-technology/green-roofs/benefits.htm. Accessed 9 Nov. 2020.
Muller, Natalie, et al. “Urban and Transport Planning Related Exposures and Mortality: A Health Impact Assessment for Cities.” Environmental Health Perspectives, vol. 125, no. 1, Jan. 2017, pp. 89–96. EBSCOhost, doi:10.1289/EHP220.
Nowak, David J. and Gordon M. Heisler. “Air Quality Effects of Urban Trees and Parks.” National Recreation and Park Association, 2010, www.nrpa.org/uploadedFiles/nrpa.org/Publications_and_Research/Research/Papers/Nowak-Heisler-Research-Paper.pdf.
“Reduce Urban Heat Island Effect.” Environmental Protection Agency, 2020, www.epa.gov/green-infrastructure/reduce-urban-heat-island-effect. Accessed 12 Nov. 2020.
“Reducing Stormwater Costs through Low Impact Development (LID) Strategies and Practices.” Environmental Protection Agency, 2007, www.epa.gov/sites/production/files/2015-10/documents/2008_01_02_nps_lid_costs07uments_reducingstormwatercosts-2.pdf
Salizzoni, Emma, and Rocío Pérez-Campaña. “Design for Biodiverse Urban Landscapes: Connecting Place-Making to Place-Keeping.” Palaeontologia Polonica, vol. 65, no. 1, Jan. 2020, pp. 126–145. EBSCOhost, doi:10.13128/rv-7641.
“68% of the world population projected to live in urban areas by 2050, says UN.” United Nations Department of Economic and Social Affairs, 2018, www.un.org/development/desa/en/news/population/2018-revision-of-world-urbanization-prospects.html. Accessed 8 Nov. 2020.