Introduction
Nowadays, rapid climate change occurs due to active urbanization, as the growth of cities contributes to the urban heat-island effect (Gill et al., 2007). City trees play a critical role in ameliorating the heat-island effect and in removing particulate matter (PM) from the air (Gill et al., 2007). Consequently, increasing the number of city trees in spatial design could be a viable solution to reducing the pace of climate change and improving the quality of air in large cities, which combines a variety of natural processes that directly affect human health and the environment (Willis & Petrokofsky, 2017). Thus, city trees have become a popular topic of research, with many studies aimed at determining the ecological and health benefits of increased tree cover. This essay will focus on city trees as a specific type of natural capital and assess its role in dealing with climate change.
The perspective in Science by Willis and Petrokofsky (2017) discusses the beneficial nature of city trees, and I have distilled the following proposition from their work: City trees, which are a part of a city’s natural capital, can help to improve urban health and environment. According to the authors, this effect is achieved due to a number of processes. For instance, trees contribute to the sequestering of carbon dioxide, thus reducing the urban heat-island effect (Willis & Petrokofsky, 2017). Furthermore, trees reduce air pollution, which has a positive impact on human health (Willis & Petrokofsky, 2017). The authors, thus, underline the importance of city trees in the mitigation of climate change and improving peoples’ well-being.
Nonetheless, research also suggests that the use of city trees for improving human health and the environment has a number of limitations. For example, Willis and Petrokofsky (2017), discuss the role of leaf structure in the trees’ capacity to improve air quality, thus showing some tree species are more effective in reducing pollution. Furthermore, Frumklin and McMicheal (2008) argue that the growth in tree cover could promote a higher rate of BVOC emissions and an increase in pollen concentrations, which would have a negative impact on human health and the urban environment. The main part of the essay will seek to discuss the key research findings and weigh the proposed arguments, whereas the conclusion will outline an informed perspective on the use of city trees for improving urban health and the environment.
Advantages and Limitations of City Trees
To discuss the role of city trees, their main benefits must be determined. Firstly, having relatively many city trees helps to reduce pollution (Willis & Petrokofsky, 2017). For instance, the London plane-tree can contribute to cleaning the air. This attributes to its capability to “shed its bark” (Willis & Petrokofsky, 2017, p. 375). The researchers emphasize that city trees naturally filter and reduce the percentage of PM in the air by absorbing pollution by stomata or by interfering with air-borne particles. Additionally, Frumklin and McMicheal (2008) see trees as key players to mitigate the pollution. To apply these concepts in landscape design, Tzoulas et al. (2007) reveal a high interference between urban green space (e.g., environmentally friendly spatial design and city trees) and ecosystems. One of the major aspects of urban green spaces is their focus on reducing pollution and providing clean air, which is a basic human need, and this can be reached by redesigning city space and prioritizing city trees. However, climate change drivers are more complex, and many factors have to be considered to introduce adjustments.
Willis and Petrokofsky (2017) also argue that city trees have a positive impact on the physical and mental health of the population. For instance, researchers discuss one of the prior studies that linked the increase in mortality from cardiovascular and respiratory diseases to a substantial loss in city trees (Willis and Petrokofsky, 2017). The authors also discovered a strong correlation between the abundance of city trees and the number of prescriptions for depression medications: Willis and Petrokofsky (2017) conclude that an increase in tree cover substantially reduces the number of medication prescriptions for depressive disorders. World Health Organisation (WHO) (2014) prioritizes dealing with pollution while an increase in city trees is likely related to the subsequent decline in the prevalence of diseases, caused by pollution and UV-radiation. These findings show that city trees not only positively affect physical conditions, but they also contribute to mental health and increase interest in exercise and sports.
Frumklin and McMicheal (2008) also state that the pollution-reducing capabilities of trees co-exist with such positive effects as the promotion of a healthy lifestyle by diversifying city landscapes with green recreational areas. This advantage pertains to the ability of trees to reduce pollution by minimizing airborne PM in the air and controlling CO2 emissions (Frumklin & McMicheal, 2008). Furthermore, PM and CO2 emissions in the air are associated with the development of cardiovascular and respiratory diseases that are worldwide related to high mortality rates. According to Frumklin and McMicheal (2008), any activities oriented to reducing PM and CO2 emissions can contribute to improving people’s health while preventing premature and pollution-related deaths, the development of chronic bronchitis, and other respiratory diseases, as well as the development of cardiovascular disorders. From this point, according to researchers, when planting trees in urban areas, it is possible to reduce air pollution, prevent the development of associated diseases, promote physical activities, and address climate change.
Willis and Petrokofsky (2017) also argue that planting the wrong species in cities has adverse consequences. They elaborate on this argument and claim that the effectiveness of PM reduction strongly depends on tree types (Willis & Petrokofsky, 2017). This problem exists since leaves and their stomata have different structures that define their different pollution-cleaning capabilities. Thus, investing in inefficient trees is cost-ineffective, as this raises other costs and implies that planting the wrong species is economically inefficient (Matthews et al., 2015). Furthermore, releasing more airborne pollen causes allergies, and birch and cypress trees are often viewed as trigger allergic reactions (Willis & Petrokofsky, 2017). Therefore, in addition to accentuating benefits, researchers also pay attention to some weaknesses in the proposition to focus on planting trees in cities.
Moreover, the researchers state that certain tree species can also contribute to the emission of biogenic volatile organic compounds (BVOCs) that usually participate in the creation of non-methane volatile organic compounds that, in their turn, lead to chemical changes in the atmosphere, particularly in the troposphere layer (Willis & Petrokofsky, 2017). These processes affect not only climate change but also human health because of decreasing the quality of air and provoking the development of such disorders as asthma, throat irritation, and the inflammation of airways. However, Willis and Petrokofsky (2017) also pay attention to the fact that, in big cities like New York and London, the authorities are aware of this problem, but they still plant these tree species by considering regional specifics, and they do not warn people about possible allergies and health risks. This discussion specifies a clear dilemma: Should the government prioritize health or simply focus on planting trees of all species to ameliorate the environment?
Lastly, Willis and Petrokovsky (2017) are correct by stating that, apart from the beneficial nature of city trees, their high density and wrong size can adversely affect the air circulation. They question their effectiveness to solve the urban heat-island effect. In turn, the wrong size diminishes trees’ pollution-reducing characteristics and keeps high PM levels. In response to these statements, Matthews et al. (2015) request a reconceptualization and modification of the existent environmentally friendly spatial designs and infrastructures. This requires sufficient evaluation of tree types and their abundance since the authorities must essentially allocate resources efficiently and choose the best options to mitigate air pollution and climate change (Matthews et al., 2015). Initiating and implementing green infrastructure initiatives does not only embed trees in urban landscapes but also deal with potential global outcomes and make cost-effective decisions.
Conclusion: Should We Consider City Trees as a Solution?
City trees are not just simple decorations, and planting more trees is a serious decision that requires careful evaluation. Natural capital is proposed as a beneficial instrument to mitigate risks that drive to climate change, air pollution, and the heat-island effect (Gill et al., 2007; Norton et al., 2014). Furthermore, Tzoulas et al. (2007) also argue that the authorities and engineers have to consider using city trees, as they sequester carbon, balance urban design, and, subsequently, ameliorate health states. However, the consulted literature also specifies the risks of increased tree cover, such as a high density of city trees, the BVOC emission, and high pollen concentrations (Frumklin & McMicheal, 2008). Overall, although the majority of studies highlight the benefits of city trees, some authors also stress the consequences of increasing tree cover. This study serves to outline the major findings of prior research studies, arguing that the health benefits and other positive effects of increased tree cover far outweigh its limitations.
I believe that Willis and Petrokofsky (2017) rightly claim that taking advantage of natural capital is complicated as selecting suitable city trees is a difficult process. Nevertheless, embedding trees in the urban environment should still be viewed as a highly important decision. Apart from having local emphasis, planting trees in cities will directly affect the environment (Frumklin & McMicheal, 2008). Such small action will also decrease local air pollution by removing PM from the streets, and this contributes to the reduction of pollution worldwide (Willis & Petrokofsky, 2017).
Meanwhile, trees and other green elements in spatial designs help the WHO to reach its health goals and decrease morbidity and mortality linked to UV-radiation (World Health Organisation, 2014). However, using these elements unwisely will worsen the existent condition dramatically. A combination of these statements poses a question: What do governments need to consider when taking full advantage of city trees? Redesigning and redefining current green infrastructure are the first steps to consider, but the process of reaching a consensus between different countries will be complex. Consequently, all cities have to define appropriate selection criteria for city trees. Revising the current green infrastructure is now necessary by the engaging society, scientists, and authorities. Let’s act green!
References
Frumklin, H., & McMicheal, A. J. (2008). Climate change and public health. American Journal of Preventive Medicine, 35(5), 403-410.
Gill, S., Handley, J., Ennos, A., & Pauleit, S. (2007). Adapting cities for climate change: The role of the green infrastructure. Built Environment, 33(1), 115-133.
Matthews, T., Lo, A., & Byrne, J. (2015). Reconceptualising green infrastructure for climate change adaptation: Barriers to adoption and drivers for uptake by spatial planners. Landscape and Urban Planning, 138(1), 155-163.
Norton, B., Coutts, A., Livesley, S., Harris, R., Hunter, A., & Williams, N. (2014). Planning for cooler cities: A framework to prioritise green infrastructure to mitigate high temperatures in urban landscapes. Landscape and Urban Planning, 134(1), 127-138.
Tzoulas, K., Korpela, K., Venn, S., Yli-Pelkonen, V., Kaźmierczak, A., Niemela, J., & James, P. (2007). Promoting ecosystem and human health in urban areas using Green Infrastructure: A literature review. Landscape and Urban Planning, 81(3), 167-178.
Willis, K., & Petrokofsky, G. (2017). The natural capital of city trees: City trees can help to reduce pollution and improve human health. Science, 356(6336), 374-376.
World Health Organisation. (2014). Climate change and human health: Global environmental change.Web.