|Initial Environmental Assessment: Urban Development - Series no 12 (NORAD, 1996)|
|Part I: Urban development. The urban environment, projects and environmental impacts.|
|3 Possible environmental impacts|
Population growth and increased concentration of people in urban areas will result in increased strains on natural resources if a sound management is not secured. Water, forestry, soil and mineral resources etc. which are vital for urban economic development can easily be excessively exploited and be lost. Deforestation, erosion, changes to the groundwater table and various other impacts may be the result. Land use conflicts in the urban fringe are common, for instance through development projects being implemented on agricultural areas or areas used for other natural resource exploitation or recreation. The impacts of urban utilisation of natural resources and areas may be found far away from the city limits.
The urban need for building materials may function as an example. Use of concrete and bricks may represent a substantial pressure on gravel, sand and clay resources. Impacts may be considerable for landscape, vegetation, groundwater, etc. (see booklet 10 "Mining and extraction of sand and gravel"). Currently a large portion of the global economy is spent on materials for buildings, including construction, maintenance of houses, offices etc.. A considerable percentage of the global resources of wood, minerals, water and energy is used for construction purposes. Much of this consumption takes place in industrial countries, but construction activities are also increasing in several developing countries. Many environmental impacts caused by buildings occur before the buildings are put into use - through construction activity, production of building materials, and transport. In addition the operation and running of many modern buildings may require large amounts of energy.
Both construction and destruction of modern buildings generate large amounts of waste. A reduction of materials used may have potential long-term impacts on local and global environment and natural resources. Both reuse and recycling of materials are relevant. Reuse is defined as using material components, for instance roof tiles, again in their entirety. Recycling means that the components are broken down to their single constituent parts which are then used again, like for instance melted copper from electrical circuits. Both loss of materials and consumption of energy can be reduced. To the degree it is possible, materials and design which are adapted to local conditions and access local natural resources should be chosen during construction. In tropical areas, for instance, soil and woven palm leaves etc. represent possible construction materials. These can be recycled by nature itself when they have served their duty (cf. also 2.1).
An ecologically sound use of materials may entail:
· that choice of technology is done closer to the user, and that production takes place in smaller industries in the vicinity of the user,
· that consumption of raw materials is based on renewable resources or rich stock resources, and that products are suitable for recycling and material-saving constructions,
· that production processes using less energy and durable materials are preferred, and that transport distances are made as short as possible, and
· that polluting industrial processes and materials are avoided, and that consumption of energy based on fossil fuel is kept as low as possible.