Week 8: Role of Plants

When you look at trees in parks or around busy cities, you focus on the aesthetic of it. How it brightens up your mood, how the smell of the trees opens up your airways, and how the green and colorful flowers break the visual block of the stone and brick buildings around you. What you DON’T think about, is the greater role of these plants.

Urban city planners intentionally include plants in their city plans for the following strategic reasons.

Ozone Layer

According to Latest News, for every 10% increase in urban tree canopy, ozone is reduced by 3-7%. Trees are also proven to remove carbon from the air, getting absorbed and stored as cellulose in their trunks, branches, and leaves (a process known as sequestration). “A single mature tree can absorb CO2 at a rate of 21.6 KG/year and release enough oxygen back into the atmosphere to support 2 humans - those are numbers to be paid attention to” (“Why We Need Trees in Our Cities”). Research has also shown a 60% reduction in particulates from car exhaust fumes on streets lined with trees.


Rain Water

Additionally, leafy tree can absorb up to 450 litres of water through its roots every day, as well as capturing rain water on the surface of its leaves (“Building Greener Cities”). Their roots also reduce soil erosion in the ground and slow the filtration of water into our cities drainage networks. This is particularly important in cities where a large proportion of the grounds surface is made up of impermeable materials, like tarmac and concrete. When we get a sudden downpour, this can quickly cause flash flooding if the water has nowhere to go. This is when trees come into play in these environments.

Energy Conservation

Trees are most effective when located to shade air conditioners, windows, or walls and when located on the side of the home receiving the most solar exposure. In a study released in August 2001, American Forests found that tree cover in the metro Atlanta area saved residents approximately $2.8 million annually in reduced energy costs (What Is Urban and Community Forestry?). In 1999, a 3.2 million acre area around Houston was found to benefit by $26 million annually as a result of the cooling effects of its tree cover. These effects of having plants conserve energy for rural areas.

Works Cited

“Building Greener Cities: Nine Benefits of Urban Trees.” Food and Agriculture Organization of the United Nations, www.fao.org/zhc/detail-events/en/c/454543/.

What Is Urban and Community Forestry? www.envirothon.org.

“Why We Need Trees in Our Cities.” Latest News, www.smartcitiesdive.com/ex/sustainablecitiescollective/why-we-need-trees-our-cities/1100050/.