[INFORMATIVE] The Role of Urban Green Spaces in Mitigating Climate Change

The Role of Urban Green Spaces in Mitigating Climate Change

By: Sahasra Gongidi

Contemporary metropolises depend largely on vegetation for their very survival. This not only gives the cities of today a vestige of nature but also intersperses them with places where any bit of vegetation can thrive. Urban green spaces, in the form of parks and gardens and the still-emerging green roofs, serve many purposes. They provide recreational areas for residents and a still-underappreciated aesthetic appeal. They also help mitigate climate change in a few significant ways.

The phrase urban heat islands (UHIs) refers to areas in and around cities that compare unfavorably to rural places in terms of temperatures. Being in a city is, in effect, a little like being in a microwave oven—not as hot as in a sauna or steam room but hot enough to be uncomfortable, especially as summer days stretch out. Buildings, roads, and other infrastructure hold and retain heat. We are in a vicious cycle of human activity and climate change that increases energy consumption and emissions, both of which exacerbate public health problems. The city of New York does not have this problem as intensely as many other cities do, but we still have fountain envy.

Roofs that have vegetation on them—a kind of living roof—are not cool roofs per se, but they are certainly much cooler than any type of conventional roof. The vegetation transpires, and the combination of that cooling effect plus the ambient air in the urban canyon is far less hot than what lies behind a conventional roof. Indeed, a good green roof can substitute for a lack of cool roofs in a largely untapped hot-urban-canyon area.

The pollutants that dominate urban areas—mostly from traffic and industry—are absorbed by plants and trees. They take in the terrible trio of carbon dioxide, nitrogen dioxide, and particulate matter. When you look at a plant in the city or in a suburb, you can see it is not just a decoration but a part of the city's life-support system. By acting as a natural air filter, a plant can perhaps reduce some of the pollution we see and breathe. The process is a little like meditation: as one inhales, the other must exhale. Plants take in CO2, which is poisonous to us. They filter it, and then, through the amazing process of photosynthesis, they convert it to oxygen.

Biodiversity is crucial for both the resilience of ecosystems and the holistic health of the environment. A variety of means, all related to enhancing different types of biodiversity, are employed to promote this outcome in urban green spaces. Creating diverse habitats for different species of plants, birds, insects, and other forms of wildlife is the first of these means. The habitats that urban green spaces create largely function as oases of biodiversity within the city, allowing different types of species to exist alongside one another. The "green oasis" that a park or garden provides or the "quasi-wilderness" that a green roof represents help make the city a more biophilic space. By biophilia, we mean the love of life or living systems that we humans are inclined toward.

How can the creation and preservation of urban green spaces serve as a counter strategy against climate change? The authors of this study uphold three main counterstrategies. First is the integration of green infrastructure into urban design. The study defines green infrastructure as "a network that integrates elements such as green roofs, vertical gardens, and pervious pavements," among others. It is a step forward from more traditional stormwater management practices that rely on "pipes and concrete." The second counter strategies involves zoning. By instituting certain kinds of zoning regulations, planners can require developers to include green spaces in their projects. The third and final strategy has to do with policies that mandate the use of certain topographical features—such as hills, dales, or cliffs—that approximate the "natural" advantages of particular kinds of green spaces.

For urban green spaces to be successful and sustainable, it is essential that the community is involved. Local people and organizations can take the lead in establishing and maintaining these areas. One way they do this is by creating community gardens, which allow local residents not only to grow fresh produce but also to rehearse the art of urban ecology. When well-managed community gardens contribute so much to the urban environment that the first half of “community garden” could be just as easily substituted with “urban garden.” Another way that local organizations work with residents to green their neighborhoods is through tree-planting campaigns.

Green spaces in cities play a vital role in countering climate change. They do this in several ways. Through evaporative cooling, they reduce the intensity of the urban heat island effect. They improve air quality by intercepting particulate matter and sequestering carbon. They increase biodiversity, which is good for both ecosystems and human communities. Because of these and other benefits, they are sometimes referred to as "climate smart" interventions.

But creating and maintaining these vital spaces is a big challenge for urban planners, architects, and designers. Some research indicates that more than half of the population in the developed world will be living in cities by 2030, and we see ongoing urbanization even in many developing countries. The new spaces formed as a result of this growth—and the old ones, too—need to become more and better integrated.


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