Protected Trees
The benefits of urban trees
Introduction
Trees and woodlands are of vital importance in maintaining and improving the quality of life of those who live and work in the Borough. Trees are one of the most obvious of our natural assets, by virtue of their sheer size and prominence.
Because they do not last forever and are vulnerable to changes in their surroundings, it is our duty to ensure that future generations are able to enjoy the many benefits that trees bring to our environment.
Cost and benefit
Trees confer many benefits and are considered as being essential to our well being and generally enhancing our built and natural environments. Trees in towns bring with them both benefits and the associated costs of maintaining them properly. Whilst many of the costs are well known to those responsible for urban trees the benefits can sometimes be seen as indistinct and difficult to quantify or justify. Nevertheless, a considerable and expanding body of global research exists on the benefits that urban trees provide to their communities.
The Council recognizes the important contribution trees and woodlands make to the environment of Fareham and are committed to the responsible and sustainable custodianship of this valuable resource. Below we have attempted to provide a summary of the many benefits of urban trees.
Social Benefits
Strengthening communities
People gain a great deal of satisfaction from growing and planting trees, caring for them and sharing that experience with others. A strong sense of ownership can develop between individuals and their personal trees, vandalism is less common and the sense of individual and communal achievement builds confidence. Success with trees can help to encourage people to deal with other shared aspects of the local environment.
Education
Trees and woodlands can be used as an educational resource. It is possible to relate them to the national curriculum and to use them in teaching a wide range of topics, from biology and geography to maths, languages, art and design. Equally importantly, children (and adults) learn through play, adventure and exploration. Easy access to trees and woodland provides a vital facility for both formal and informal learning in the urban environment.
Other social benefits
A wealth of research has been undertaken in the United States that has identified numerous beneficial effects that trees have on society. Many of these benefits relate to encouraging people out of their homes and into public open space, where they react more with others and build stronger social relationships.
Office workers who can see nature from their desks were found to experience less time off sick than those who can not see any nature. Desk workers who can see nature also report greater job satisfaction, whilst hospital patients with views of trees have been found to recover significantly faster than those who can not see any natural features.
Environmental Benefits
Wildlife and biodiversity
Whilst all vegetation is of some benefit to wildlife, there is evidence that in general, species with a long established presence in a region support the greatest variety and biomass of insects, and thus the birds and other creatures which depend on them. By favouring such native or long established species of trees in new planting, it is possible to accommodate more wildlife.
Different kinds of wildlife will thrive in different types of woodland and the structure of woodland is also influential in terms of species diversity.
In an urban setting, linear corridors of habitat are among the most important, connecting otherwise isolated areas to each other and beyond, out into the rural surroundings and countryside. Trees and other vegetation along highways, waterways and railways are particularly important to wildlife in this respect.
Pollution interception
Research undertaken in the UK has established that trees can remove a number of pollutants from the atmosphere, including ozone, nitrogen dioxide and particulates. However, trees also produce volatile organic compounds, VOCs, which in combination with some man made pollutants can lead to an increase in ozone, particulates and other pollutants.
Different species of tree can have a different net effect on air quality. Willows, poplars and oaks can potentially worsen air quality during hot weather, whilst ash, alder and birch have amongst the greatest beneficial effects.
Carbon sequestration
It is well known that trees, in common with all vegetation, absorb carbon dioxide (one of the principal greenhouse gases) and release oxygen during the process of photosynthesis. The carbon absorbed by trees in this process is stored in the wood.
However, whilst this most well known of benefits is real it seems that it is sometimes overstated. A study by Lancaster University of trees in the West Midlands estimated that the total amount of carbon stored in trees within the conurbation represents the equivalent of about three weeks worth of CO2 emissions. Never the less, trees do have an important role to play in reducing the effects of greenhouse gases, not only through carbon sequestration but perhaps more importantly through the effects that careful planting can have on fuel use.
Fuel use
Careful tree planting can reduce the amount of fuel used for both heating and cooling buildings. A considerable amount of research has been undertaken to quantify this in the United States, but little such research has been undertaken in the UK. Clearly differences in climate mean that figures here can not be directly related to any part of the USA.
Trees provide shelter and reduce wind speed, thus reducing heat loss from buildings during winter. They also provide shade in the summer, whilst the eva po-transpiration of water from the leaf surface has a general cooling effect on surrounding air. This can significantly reduce the need for air conditioning during hot weather.
Noise reduction
Trees and other vegetation can play an important role in attenuating noise through reflecting and absorbing sound energy. One estimate suggests that 7db noise reduction is achieved for every 33m of forest, whilst other reported field tests show apparent loudness reduced by 50% by wide belts of trees and soft ground.
Hydrology
The canopy of the urban forest plays a valuable role in reducing the impact of rain storms. The rain is intercepted by the leaves and then evaporates or drips gradually to the ground. This lessens the likelihood of flash – flooding and helps to conserve ground water. Perhaps the most important effect in Britain at present, given the trend for increasingly intense rainfall, leading to flash - flooding, is the reduction in ground water run-off. One study has estimated that for every 5% increase in tree cover area, run-off is reduced by 2%. Using trees in towns as part of a storm - water management strategy is a self sustaining and cost effective remedy, which should be used to compliment more expensive hard - engineering options.
Economic Benefits
Inward investment
The attractiveness of an environment is an important factor in attracting inward investment. Both consumers and businesses have been found to favour districts with high tree cover and the increase in retail prices that can be commanded in well landscaped areas can reasonably be assumed to be a positive benefit in attracting businesses to the area.
Property values
Several studies, principally in North America, have analysed the effect of tree cover on the average price of residential house sales, finding that values of properties in well - treed areas are between 5% and 18% higher than in similar areas without mature trees.
The market in the UK is different and a direct comparison with this data is not available. Never the less, there are some financial benefits which are clearly attributed to trees and more than just anecdotal evidence that properties in tree lined areas are said to be in higher demand and sell faster.
If you would like any further information please contact the Arborist within the Department of Planning and Transportation on Tel: 01329 236100 or e-mail conservation@fareham.gov.uk
References
Coder, KD, 1996, Identified Benefits of Community Trees and Forests, University of Georgia Cooperative Extension Service - Forest Resources Publication FOR96-39
Dwyer, JF, McPherson, EG, Schroeder, HW and Rowntree, R, 1992, Assessing the Benefits and Costs of the Urban Forest, [in] Journal of Arboriculture 18(5), pp 227 - 234.
Hewitt, N, Stewart, H, Donovan, R and MacKenzie, R, undated. Trees and Sustainable Urban Air Quality, Research summary from Lancaster University at http://www.es.lancs.ac.uk/people/cnh/docs/UrbanTrees.htm
Kuo, FE and Sullivan, WC, 2001(a), Environment and Crime in the Inner City. Does Vegetation Reduce Crime [in] Environment and Behavior 33(3), pp 343 - 367
Kuo, FE and Sullivan, WC, 2001(b), Aggression and Violence in the Inner City - Effects of Environment via Mental Fatigue, [in] Environment and Behavior 33(4), pp 543 - 571
Kuo, FE, 2003, The role of Arboriculture in a Healthy Social Ecology [in] Journal of Arboriculture 29(3), pp148 – 155
Learning through Landscapes (1992) Trees in school grounds
Morales DJ (1980) The Contribution of Trees to Residenetial Property Value [in] Journal of Arboriculture 6(11): pp 305 - 308
National Urban Forestry Unit (1998) Tree Matter – The Benefits of Trees and Woods in Towns
Nowak, DJ, undated, The Effects of Urban Trees on Air Quality, USDA Forest Service, Syracuse, NY
Wolf, K, 1998(a), Trees in Business Districts - Positive Effects on Consumer Behaviour, University of Washington College of Forest Resources, Fact sheet #30.
Wolf, K, 1998(b), Trees in Business Districts - Comparing Values of Consumers and Business, University of Washington College of Forest Resources, Fact sheet #31.
Wolf, K, 1998(ac), Urban Forest Values: Economic Benefits of Trees in Cities, University of Washington College of Forest Resources, Fact sheet #29.
Wolf, K, 1998(d), Urban Nature Benefits: Psycho-Social Dimensions of People and Plants, University of Washington College of Forest Resources, Fact sheet #1.
Wolf, K, 1999, Grow for the Gold, [in] Tree Link 14, Washington State Department of Natural Resources
Wolf, K, 2000, Community Image - Roadside Settings and Public Perceptions, University of Washington College of Forest Resources, Fact sheet #32.
Wolf, K, 2003, Public Response to the Urban Forest in Inner-City Business Districts, [in] Journal of Arboriculture 29(3) pp 117 - 126
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