The benefits of urban trees

[edit] Introduction

Trees and urban green infrastructure are a core aesthetic and environmental component of the urban landscape. Unfortunately, until recently the common attitude to urban trees was not to place them in the centre of initial planning, but rather to treat them as an optional addition to a completed project.

Attitudes are changing now. Good urban planning and placemaking tend to take advantage of the existing green infrastructure and provide space and place for planting more trees and greenery.

The importance of green urban forests is difficult to overestimate: it influences all major areas of residents' wellbeing from physical health, to the level of a community's engagement and mental wellbeing. The potential benefits must be estimated at the initial phase of planning, and green infrastructure should be central to any development.

[edit] Environmental benefits

• Tree canopies provide valuable habitat for all kind of species, helping restore and maintain healthy species diversity.
• Trees prevent soil erosion, protecting urban hillsides and slopes from the destructive force of rainwater.
• Trees produce oxygen. An acre of mature trees can generate enough oxygen for 18 people a year.

[edit] Regulating urban climate

Trees play a vital role in the temperature regulation of cities. Research undertaken by the UK Forestry Commission shows that trees and green infrastructure can reduce the urban heat island effect (UHI), and can cool air by between 2ºC and 8ºC. This can be life saving. According to the same research, during hot summers the UHI effect is the cause of heat-related stress, which accounts for around 1,100 premature deaths a year in the UK.

Urban trees are an effective tool in cooling down cities and towns, fulfilling three important functions:

• They use solar energy to convert water inside them into water vapour thus preventing it from being transferred into the actual heat.
• They reflect heat, thus preventing it from being absorbed, stored and warming the local environment.
• They shade people and buildings from direct exposure to the sun thus reducing overheating and excessive heating through windows that creates an internal green house effect

[edit] Community benefits

Trees and green spaces are also an essential element of placemaking, they are central to creating public realms that draw people in and bring communities together.

A 2001 study [1] of a Chicago public housing development showed a dramatic reduction in crime in apartment buildings surrounded by trees and greenery compared to the nearby identical apartment block surrounded by barren land. The study revealed a significant 48% reduction in property crime and a 56% reduction in violent crime.

Green infrastructure reduces crime in several ways:

• Urban trees produce a more relaxing environment reducing anxiety and aggression.
• Trees and greenery encourage people to spend more time outdoors increasing surveillance and discouraging antisocial behaviour.
• Green and landscaped urban areas inspire higher levels of the residents' attention and involvement in watching over the property and each other.

[edit] Economic benefits

Tree-lined areas and retail districts with enhanced green infrastructure create an attractive environment that encourages shoppers to linger longer.

Trees also make a significant contribution to the value of property in a neighbourhood.

[edit] Urban tree canopy: taking stock for better urban planning

In the UK, levels of urban deforestation have been increasing for the last 30 years.

In an attempt to reverse this trend, the urban canopy initiative (UK UCI) was launched in 2008. The initiative set the following objectives:

• Identifying why trees are being lost.
• Investigating how canopy loss can be reversed.
• Documenting viable solutions.
• Establishing a mechanism for disseminating those solutions.
• Lobbying government for a coordinated strategy to increase urban canopy cover.
• Monitoring, reviewing, delivering, and reporting on progress.

Taking stock of the existing urban canopy is vital in identifying the ways to maintain and support urban forests. This type of survey answers the main questions that form the basis of urban tree policy:

• How many healthy and mature trees does an area have?
• Is the number enough for the local residents to benefit?
• Which species thrive in the area and which don't?
• Which trees should be planted in the area to enhance its green infrastructure?
• What are the best places for planting?

[edit] Urban trees survey in Wales

The 'Tree Cover in Welsh Towns and Cities study' was designed to help address the lack of knowledge and accountability as far as Wales' urban trees are concerned. The study also provided a valuable insight into how trees contribute to the quality of those most used places in towns and cities.

This has paved a way to understanding what green resources Welsh cities and towns already have. This invaluable information provides planners and urban designers with a context in which they can plan redevelopment projects and new built areas.

[edit] Related articles on Designing Buildings

• Definition of tree for planning purposes.
• Deforestation.
• Forests.
• Forest ownership.
• Green roof.
• Green space.
• Green walls.
• Landscape officer.
• Placemaking.
• Planting.
• Rain garden.
• Timber.
• Tree dripline.
• Tree hazard survey.
• Tree preservation order.
• Tree rights.
• Urban heat island effect.
• Urban trees.

[edit] External references

1. Kuo, F.E., & Sullivan, W.C. (2001). “Environment and crime in the inner city: Does vegetation reduce crime?” Environment and Behavior, 33(3), 343-367.