Urban trees face a range of challenges brought about by the restricted and usually paved areas in which they must exist. In cities trees increasingly have to share above ground space with pedestrians and cars and below ground space with utilities of many kinds.
Challenges to healthy tree growth include compacted soil, lack of water and oxygen, excessive wind forces and damage from vehicles and vandals. Tree roots have to accommodate the close proximity of underground infrastructure and related excavations as well as pavements and roadways.
Finding landscape solutions to these challenges is well justified by the innumerable benefits conferred by trees in the urban environment as described Nowak, Stein et al (2010) . For the conterminous United States, the benefits and estimated annual savings in 2010 include:
- Real estate and business—Landscaping with trees, in yards, in parks and greenways, along streets, and in shopping centres, can increase property values and commercial benefits. One study found that on average, prices for goods purchased were 11%higher in landscaped areas than in areas with no trees;
- Individual well-being and public health—Urban trees and forests can make the environment a more aesthetic, pleasant, and emotionally satisfying place in which to live, work, and spend leisure time. Urban trees also provide numerous health benefits; for example, tree shade reduces ultraviolet radiation and its associated health problems, and hospital patients with window views of trees have been shown to recover faster and with fewer complications than patients without such views;
- Community well-being—Urban forests make important contributions to the economic vitality and character of a city, neighbourhood, or subdivision. A stronger sense of community and empowerment to improve neighbourhood conditions in inner cities has been attributed to involvement in urban forestry efforts.
- Noise abatement – properly designed plantings of trees and shrubs can significantly reduce noise. Wide plantings of tall dense trees combined with soft ground surfaces can reduce apparent loudness by 50% or more;
- Wildlife and biodiversity – urban forests help create and enhance animal and plant habitats and can act as reservoirs for endangered species. Urban forest wildlife offer enjoyment to city dwellers and can serve as indicators of local environmental health;
- Local climate and energy use – trees influence thermal comfort, energy use and air quality by providing shade, transpiring moisture and reducing wind speeds (saving $2b in reduced energy costs);
- Air quality – trees improve air quality by lowering air temperatures, altering emissions from building energy use and other sources and removing air pollutants (value $3.8b).
Urban trees are increasingly raised in the context of climate change because they directly store carbon within their tissues and reduce carbon emissions from power plants through lowered building energy use (saving $14.3b). Trees and soils also improve water quality and reduce the need for costly storm water treatment by intercepting and retaining or slowing the flow of precipitation reaching the ground. Water Sensitive Urban Development treepits, for example, can dramatically reduce potential runoff and channel water to tree roots. Finally trees and other plants help remediate soils at landfills and other contaminated sites by absorbing, transforming and containing a number of contaminants.
Citygreen offers landscape solutions to many challenges affecting healthy urban trees, starting with the provision of adequate, uncompacted soil able to provide nutrients for the tree as well as support pavements and roads. A range of root guidance products enable tree roots to be managed effectively, kept away from utilities and protected during building works.
Above and below ground solutions are available through Citygreen to provide tree support and protection. Our range of tree guards and grilles are both functional and aesthetic, enhancing the streetscape whatever its character. Deep watering and aeration systems ensure the provision of adequate water and oxygen at all times, while rainwater harvesting applications can save water, improve quality and support healthy tree growth at the same time.
 D.J. Nowak, S.M.Stein, P.B.Randler. E.J.Greenfield, S.J.Comas, M.A.Carr and R.J.Alig, June 2010,Sustaining America’s Urban Trees and Forests, United States Department of Agriculture Forest service, General Technical Report NRS-62.