BrisUrbane

For a Better Brisbane

The value of trees & green spaces 2


Trees are a valuable part of the urban landscape. The above video explains some of the benefits in urban areas. Firstly trees remove pollution from the air and improve air quality. Pollutants removed include Ozone, fine airborne particulate matter (PM10), Nitrogen dioxide, Sulfur dioxide and Carbon monoxide. (1) Secondly, through transpiration they can make a more pleasant urban environment and dampen the ‘heat island effect’, and thirdly the shade cast by trees can mean that nearby buildings don’t have to spend so much money on air conditioning (which in turn means less emissions at the power plant). There is also some evidence that trees can increase the life of road asphalt.(2)

In 1994, trees in New York City removed an estimated 1,821 metric tons of air pollution at an estimated value to society of $9.5 million. Air pollution removal by urban forests in New York was greater than in Atlanta (1,196 t; $6.5 million) and Baltimore (499 t; $2.7 million), but pollution removal per m2 of canopy cover was fairly similar among these cities (New York: 13.7 g/m2/yr; Baltimore: 12.2 g/m2/yr; Atlanta: 10.6 g/m2/yr)

– The effects of urban trees on air quality, D.J. Nowak, USDA Forest Service, paper here

Not just any tree will do, as some species of tree actually seem to emit pollution (volatile organic compounds) into the air. See here.

Trees also have a positive impact on the market sale price of properties. Research done at QUT looked at a lower-middle class suburb in Christchurch, New Zealand, and using sales records from the Real Estate Institute of New Zealand, compared sales of properties on main roads, poor streetscapes and good streetscapes. In the study’s conclusion:

If all other purchase criteria are equal, such as age of the house, size, construction and
location and there are no external features such as views of parks, water, mountains or
rural landscapes, then simple factors such as tree plantings in a street can have a
significant impact on house prices.

In poorer socio-economic areas houses in streets with a good street appeal based on
tree plantings will sell for a higher price on average and also show a higher average
annual capital return at a lower level of risk compared to all other houses in the same
location.

Assessing the impacts of streetscape on residential property in lower to middle socio-economic areas, Eves, C (See ref. 3)

This blog isn’t arguing that every tree is untouchable. They are not. Nor is this necessarily an argument that developments cannot take place in or near parklands (future posts will visit some examples).

Rather, we don’t seem to realise just how valuable trees and green spaces are. Now that there are methods of putting a price on trees, where a tree has to be removed, compensation or in-kind remediation should follow. Many city councils such as the City of Sydney have now established databases and registers of their significant trees, along with dollar valuations of the the trees to ensure their ongoing protection.

More information:
Centre for Urban Forest Research

1. Air pollution removal by urban trees and shrubs in the United States, D.J. Nowak, D.E. Crane & J.C. Stevens, Urban Forestry and Urban Greening (2006), 4, p115 link here

2. Effects of street tree shade on asphalt concrete pavement performance, E.G. McPherson & J. Muchnick, Journal of Arboriculture (2005), 31 (6), p303 link here

3. Assessing the impacts of streetscape on residential property in lower to middle socio-economic areas, Eves, C., 16th Annual European Real Estate Society Conference, 24-27th June 2009, Royal Institute of Technology, Stockholm (unpublished) link here

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July 7, 2010 at 7:33 pm

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