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THE VALUE OF TREES
Trees and woodlands in urban areas provide environmental, aesthetic and cultural benefits both locally and globally. These benefits include:
Reduction in carbon dioxide levels
As trees grow they lock up carbon dioxide, one of the major 'greenhouse' gases. This is fixed in the wood, therefore trees act as sinks for carbon dioxide and help to ameliorate the 'greenhouse effect'
Production of oxygen
It is proven that a mature tree produces enough oxygen over a year to meet the annual requirement of ten people.
Filtration and absorption of pollution
Gaseous pollution, for example from nitrogen oxide, sulphur dioxide and carbon monoxide, is absorbed into plant tissue, notably leaves. Particulate pollution (notably smoke, dust and ash) is also trapped by leaves, branches and stems, and is washed off by precipitation. It is estimated that a beech wood extracts nearly five tons of dust per hectare per year.
Absorption of noise
Block planting of trees and shrubs can reduce noise levels appreciably; 5 to 15 decibels depending on the species of tree and shrub and the height and width of the planting. Moreover, trees absorb high sound frequencies, the frequencies to which humans are most sensitive.
Attraction of wildlife
People place high values on wildlife in urban areas. Trees provide homes for many species of flora and fauna that could not survive in the alien environment of a city. In essence the trees bring the countryside into the town. A city rich in tree species, abundance and distribution of trees will provide a habitat for a diverse wildlife population.
Improvements in landscape quality
Urban environments can detach their inhabitants from the countryside and nature. Trees provide a fundamental contact with nature and the seasons and heighten pleasure in our surroundings. They provide variety in colour, form, texture, sound, odour and patterns in the landscape. Trees also soften architectural lines and accentuate structural details, provide focal points, form vistas and define space. Trees can also add to the character of an area, and provide a sense of historical continuity.
Psychological benefits
Research has shown that, compared with an urban scene which lacks vegetation, people have a preference for views containing trees and shrubs. Trees evoke positive feelings, and reduce negative emotions such as fear, anger and sadness, and accordingly block or reduce stressful thought.
Economic benefits
The presence of trees in urban areas, particularly in streets and open spaces, can increase the value of residential and commercial property by 7 to 15%. The value of undeveloped land which has trees on it can be increased by 20 to 25%.
Trees provide shelter from cold winds and hot sunlight, thus helping to reduce heating and cooling energy requirements in buildings.
As a result of tree and woodland management, timber and brushwood are produced. These 'by-products' can be used for firewood, charcoal, mulch, landscape materials, building materials and furniture grade timber. With an eye on Agenda 21 (Earth Summit, Rio de Janeiro 1992) local authorities are investigating how the products of tree management can be recycled to generate revenue.
For an article on the financial value of trees click here.
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