Essay

2 | 2012-2013 | Volume 2

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Emmanuel Assa

nance cost [1]. his property of the Urban Heat Island is the most economically threatening [3]. he solution is still to introduce vegetation into the urban environment. he leaves of a plant have a much higher albedo than pavement or concrete, and plants release only a small amount of in-frared radiation in the form of heat [2]. he more surface area of a city occupied by pants, the less severe the Urban Heat Island. hrough this efect, planting trees and other vegetation can reduce the costs of building maintenance within a city.

he other economic beneit of integrating nature with the urban comes from the visual appeal of a city. A bet-ter-looking city can charge more for building space and property taxes, supplementing the city’s economy. Vegeta-tion makes a city more pleasant to live in because it pro-vides color against the normal grays and blacks of concrete and asphalt, and the shade it provides during the warmer months makes the city a more attractive place to live.

Green roofs are possible ways of integrating nature with the urban environment. A green roof is similar to a patch of vegetation that covers the top of a building. It increases the albedo of the building (lowering the Urban Heat Is-land Efect), and the vegetation can be drought-tolerant, minimizing the amount of water the owner would need to use to maintain it [4]. However, this limits the selection of plants available for the roof. Green roofs can be made to be aesthetic as well as functional; tropical or exotic vegetation can be added if the area is intended for recreation [4]. Pre-cautions for aesthetic green roofs are that extra structural support is needed to hold up the extra weight, and exotic plants may require additional maintenance [4]. Both types of green roofs are capable of increasing a roof membrane’s longevity, improving a building’s sound insulation, reduc-ing a building’s energy costs, and reducing the rainwater runof [4]. Plain green roofs are cheap and easy to install, but aesthetic green roofs require planning in advance so that additional supports can be set up within the building shell. he typical cost of a green roof is only around $100 to $300 per square meter. Green roofs are an easy and ef-icient way to incorporate nature into its city surroundings.

Many of the problems caused by urban sprawl can be either reduced or eradicated by introducing vegetation into the urban environment. All at once, it can improve

Modern cities are not perfect. As they expand, they be-come centers for human civilization, but also centers for civilization’s greatest problems. As more and more of the human population moves into the city, the space we need increases, causing severe urban sprawl [1]. Urban sprawl creates the Urban Heat Island Efect, along with air and water pollution [1, 2]. he Urban Heat Island Efect, in turn, increases the cost of living, reduces a city’s comfort level, and can have detrimental impacts on a city’s sur-rounding environment [1]. To improve this situation, many researchers have proposed the added introduction of vegetation into the urban environment [2]. his prac-tice will diminish pollution, reduce the Urban Heat Island, and even produce a proit for the city [2]. Integrating na-ture into the urban will produce better, cleaner, and more cost-efective cities.

For any city, pollution can be a major problem, espe-cially in the air. Smog is a common phenomenon around large cities. Smog, a noxious combination of smoke and fog, contains chemicals such as sulfur dioxide and nitro-gen oxides, key compounds in acid rain formation [2]. hese chemicals are both harmful to the lungs and odor-ous, lowering a city’s residential appeal. Introducing plants into this environment would solve the problem almost im-mediately. Many types of vegetation absorb those harmful airborne chemicals, preventing them from forming acid rain [2]. hese plants would efectively clean the surround-ing air, lowering the chance of acid rain and improving the health of the city residents.

he Urban Heat Island is one of the most-studied ef-fects of the current urban sprawl, and they key to the prob-lem lies in albedo, the relative relectivity of a material [3]. he higher an object’s albedo, the more light it relects. Concrete and asphalt, the primary modern construction building materials, have very low albedo [3]. his means that during the day, the concrete and asphalt in cities ab-sorb radiation from sunlight, and then release it at night as heat [3]. his creates a heat “bubble” around a city. Because of the increased temperature, air conditioning systems in every building inside of this “bubble” must consume more energy in order to maintain a comfortable interior temper-ature. More energy consumed means more energy bought from the power companies, which means a higher mainte-

A Photosynthetic City: Combining Nature with the Urban

Environment

2 | 2012-2013 | Volume 2

Emmanuel Assa was selected as the winner of the 2012-2013 Broad Street Scientiic Essay Contest. His award included the opportunity to interview Dr. Lefkowitz as part of the Interview section of the journal.

Essay

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air quality, reduce the cost of living in an urban area, and create a beautiful cityscape. Implementing this concept on a city-wide scale also requires very little capital. By maintaining a careful balance between nature and human constructions, we can accommodate the increasing urban population with ease.

References

[1] Golden, J. S. (2004). he built environment induced urban heat island efect in rapidly urbanizing arid regions – a sustainable urban engineering complexity. Environ-mental Sciences, 1(4), 321-349[2] Manning, W. J. (2008). Plants in urban ecosystems: Essential role of urban forests in urban metabolism and succession toward sustainability. International Journal of Sustainable Development and World Ecology, 15(4), 362-370. http://search.proquest.com/docview/197928423?accountid=12723[3] Hecht A., Fiksel J., Fulton S., Yosie T., Hawkins N., Leuenberger H., Golden J., & Lovejoy T. 2012. Rejoinder: Creating the future we want. Sustainability: Science, Prac-tice, & Policy 8(2) Published online Apr 20, 2012. http://www.google.com/archives/vol8iss2/1203-002.rejoinder.html[4] Oberndorfer, E., Lundholm, J., Bass, B., Cofman, R. R.; et al. (2007). Green roofs as urban ecosystems: Ecolog-ical structures, functions, and services. Bioscience, 57(10), 823-833.