Source: Spectrum Colour Library
THE PROBLEM |
Important changes in the quality of the urban environment have occurred in Europe in the last few decades. Despite the progress achieved in controlling local air and water pollution, urban areas show increasing signs of environmental stress (Chapter 10). Major concerns for European cities are the quality of air, acoustic quality and traffic congestion. Open spaces and green areas are under continuous threat due to more competitive uses of limited land resources. The quality of life in cities is also affected by the deterioration of buildings and infrastructure and the degradation of the urban landscape. On the other hand, cities absorb increasing amounts of resources and produce increasing amounts of emissions and waste, causing significant burdens on the regional and global environment. A summary of major urban environmental problems in Europe is presented in Box 37A. These problems are warning signals of a more deep-seated crisis, and call for a rethink of current models of organisation and urban development.
Symptoms of environmental stress in cities become evident when the quality of environmental components and their effects on the health and quality of life of the urban population are examined. However, the causes of urban stress can be understood only when examining how cities work and how their spatial organisation affects their environmental performance. The quality of the urban environment is a result of the interactions of many interdependent variables and between urban activities and city structure. The impact of urban activities on the local environment is not the sum of each effect taken individually. In cities, people are exposed simultaneously to the concentrations of pollutants into the air, water and soil. Synergies among these factors generate environmental stress. Addressing the causes of environmental problems, instead of treating their symptoms, is necessary if current efforts to improve the quality of the urban environment are to succeed.
Urban environmental problems are often referred to as local problems. The high concentration of people and activities in cities is the cause of heavy pressures on the local environment. Local environmental conditions affect the health of the exposed population. However, environmental problems affecting urban areas are closely linked with regional and global problems by their common causes and interdependent effects. Urban air pollution is linked to acidification, photochemical smog and climate change through the emissions of atmospheric pollutants from the burning of fossil fuels. As cities deplete their local resources and increase their dependence on imported global resources, they become more vulnerable to the effects of global environmental change. On the other hand, the implementation of measures to improve the urban environment have corresponding beneficial effects on the regional and global environment.
CAUSES AND CONSEQUENCES |
Urban air pollution, noise and traffic congestion are the most recognised symptoms of urban environmental stress. Causes of such stresses are clearly related to rapid changes in urban lifestyles and increased urban activities which have occurred in the last decades. Yet, their links with the patterns of urban development are often not fully appreciated. The interrelated nature of urban environmental problems can be best explained by examining, for example, the relationship between air pollution, energy consumption and transportation trends.
Major causes of air pollution in cities are the processes involving the combustion of fossil fuels. These include the production and consumption of energy for domestic and commercial building heating systems, industrial activities and transport. There are important differences in energy patterns among European cities and within cities' inner and outer areas, as illustrated by the examples of London and Berlin (Figure 37.1a, b and c). These are reflected in the levels of emissions of air pollutants and air quality levels. Fuel substitution in domestic heating has reduced dramatically the emissions of sulphur dioxide and particulates per unit of energy consumed in Western European cities. The substitution of natural gas for coal and oil in European cities has also reduced emissions of carbon dioxide per unit of energy. However, the majority of cities still exceed short-term WHO-AQGs (air quality guidelines), and in most Eastern and Southern European cities long-term exposure to particulates and sulphur dioxide is still an important concern. Furthermore, as emissions from stationary sources of urban air pollution from domestic and industrial activities have receded, traffic-generated pollutants such as nitrogen oxides, carbon dioxide, particulates and volatile organic compounds have steadily increased.
Urban traffic is an increasingly important source of urban air pollution (Figure 37.2). Road transport in cities accounts for most of the summer smog in Europe and the exceedances of WHO-AQGs for ozone, nitrogen oxides and carbon monoxide. Urban transport as a whole represents around 30 per cent of total energy consumption in most European cities, second only to the domestic sector, which accounts for one third of the urban energy consumption. Energy consumption by urban transport has almost doubled in the last two decades, and its share of total urban energy consumption is expected to increase further following urban mobility trends. Most energy-intensive transport is road transport, which accounts for more than 85 per cent of total transport energy consumption. Total fuel consumption by vehicles has increased substantially in the last decades despite the improvement achieved in their energy efficiency.
Current trends in urban mobility, and their increasing environmental impacts, are closely related to changes in the urban structure. Urban population density varies considerably from city to city, but almost all cities are experiencing decentralisation of population, whether they are growing or not (see Chapter 10). The decentralisation of urban activities traditionally located in urban centres as a result of economic specialisation, and the relocation of urban activities far from public transport links, have changed urban mobility patterns and increased car dependency of urban residents. Traffic flows in European cities have increased in terms of number and length of trips over the past decade. During the same period, the share of public transport of total motorised urban travel has fallen in most cities to about 20 per cent. The car's share of urban mechanised transport has reached over 80 per cent. These trends are major concerns in most European cities for their effects on human health and the environment.
The physical health of the European population is closely linked to environmental stress in urban areas (see Chapter 11). European urban areas are where environmental problems most affect the quality of life of citizens. Most air pollutants, such as sulphur dioxide, particulate matter, nitrogen oxides and carbon monoxide, directly affect human health. Other urban traffic-related factors of environmental stress in urban areas are noise, road accidents and congestion. Unacceptable noise levels of more than 65 dB(A) affect between 10 and 20 per cent of urban inhabitants in most European cities. Urban road accidents remain a significant problem despite the important progress achieved in the implementation of traffic safety measures. Traffic congestion has caused the reduction of average speed in urban centres by 10 per cent in the last two decades. These problems are among the most severe urban problems as perceived by people living in urban areas in a recent OECD survey of 132 cities (OECD/ECMT, 1993).
European cities contribute to local, regional and global environmental change. Major local environmental changes are the result of urbanisation and the transformation of the surface structure and thermal balance. Urban activities give rise to multiple environmental stress factors. Air pollution in cities combines with critical climatic conditions to generate high-level exposure episodes. Inner-city green areas are subject to high levels of pollution. Many historic monuments and buildings, especially those made from marble, calcareous sandstone, or other materials susceptible to damage, are affected by air pollutants. In urban air, soot and other primary particles are important contributors to visibility effects.
The state of the urban environment is inevitably linked to the state of the regional and global environment by the same causes of stress. Sulphur dioxide and nitrogen oxides emissions contribute to transboundary air pollution and increased acid deposition levels (Chapter 31). Nitrogen oxides are also precursors of ozone, which is the main constituent of photochemical smog (Chapter 32). Motor vehicles account for a considerable proportion of the total emissions of nitrogen oxides to the atmosphere in Europe, and their contribution is expected to increase in the long term following the growth in the use of the private car. Energy consumption and urban traffic are also major contributors to carbon dioxide emissions, which form the principal cause of the greenhouse effect (Chapter 27). Cities are also important sources of stratospheric ozone-depleting substances (Chapter 28).
TRENDS AND SCENARIOS |
The share of Europe's population living in urban areas is expected to increase over the next decade, with the largest cities housing a very significant proportion of the population. Urban lifestyles are already predominant in all European countries despite regional differences in the level of urbanisation and stage of urban development. Distinct phases of urban environmental problems in Europe can be associated with various stages in urbanisation. Urban air pollution in European cities can be related to the level of urban development as illustrated schematically in Figure 37.3. During the period of rapid urbanisation, air pollution levels rose rapidly, mainly from domestic and industrial sources. Switch in fuel use and the introduction of emission control measures have emerged as air pollution in European cities becomes a serious public concern. This has led to stabilisation of air quality condition and successive improvement. Suburbanisation and de-urbanisation, accompanied by a sharp decline in the manufacturing industry in the main Western European conurbations, have led to further improvement in air quality and a drastic reduction in emissions from industrial and domestic sources. However, the decentralisation of economic activities traditionally located in urban centres has contributed to the growth in travel demand and the use of the private car, which constitutes an increasing source of air pollution in cities. The current process of re-urbanisation is now accompanied by new air pollution concerns.
Future environmental conditions in European cities are highly dependent on the sustainability of economic development and the introduction of new technologies. While there is a paucity of information available to demonstrate the impact of regulations aimed at controlling individual emission sources, observed trends in sulphur dioxide, nitrogen oxides and lead concentrations show evidence of the effectiveness of these measures. Emission controls have been particularly successful in the reduction of dust and fly-ash emissions to the atmosphere, and in the reduction of the emissions of gases from process industries. To a large extent the exceedances of air quality guidelines for sulphur dioxide and suspended particles in European cities can be attributed to the burning of coal in small domestic stoves and boilers, and to uncontrolled emissions of dust from industrial sources. This is still a major problem in Central and Eastern European cities because of their heavy reliance upon coal typically poor-quality brown coals and lignite. The supply of cleaner fuels, such as natural gas and low-sulphur distillate oil, to domestic heating applications and dust removal from industrial sources and larger boilers, together with increased energy efficiency, is expected to produce major improvements.
Although detailed emissions inventories for most European cities are not available, observed trends in national emissions inventories show that emissions of nitrogen oxides from stationary sources have decreased in many urban areas, while emissions from motor vehicles have increased, since the growth in traffic and road transport has been much larger than the reduction in emission factors. Motor vehicles are already the major source of urban air pollution in most Western European cities. Although the regulation on exhaust emissions of cars and lorries is expected to reduce substantially emissions of air pollutants from individual vehicles, the projected increase in car ownership and urban travel will largely offset the potential reductions. The relative contribution of mobile sources to total air pollution load is expected to increase substantially in Eastern European cities in the next decade.
Under current policies, European sulphur dioxide emissions are expected to decrease by about 30 per cent between 1990 and 2000. For aerosol particles, including both emitted dust and soot and secondary sulphate and nitrate aerosol, future developments are uncertain. No international policy framework exists for these pollutants and even present levels are not well known. Following emission reductions of sulphur dioxide and nitrogen oxides, sulphate and nitrate aerosol levels are expected to decrease by 20 to 30 per cent. Concurrent with technological changes and shifts in fuel use, primary dust emissions from power generation and industry in Central and Eastern Europe are expected to decrease in the next 20 years by at least 30 per cent. While industrial particulate emissions are expected to decrease, the trend in future traffic emissions is uncertain, particularly with respect to soot.
Emission reductions in European cities will result in decreasing occurrence of winter smog and less pollution-induced visibility reduction. However, these reductions are not sufficient to prevent exceedance of the WHO-AQGs for sulphur dioxide and aerosol particles. This probably requires emission reductions of the order of 80 per cent, especially in hot-spot regions (eg, the Black Triangle). Significant emission reductions for dust and aerosol particles can be achieved by implementing various filtering techniques, such as electrostatic precipitators (ESP) on power plants and baghouse filters on industrial installations; fuel change from coal to gas in power production and residential heating; and energy saving.
SUSTAINABILITY GOALS |
Sustainable urban patterns are essential to achieve sustainability in Europe. These imply bringing urban activities into balance with the capacity of ecosystems to provide life support services important for human health. These also require minimising the pressure of urban activities on the local, regional and global environment. Sustainable cities are cities that provide a livable and healthy environment for their inhabitants and meet their needs without impairing the capacity of the local, regional and global environmental systems to satisfy the needs of future generations. These challenges are interdependent and require coordinated efforts.
Making cities sustainable entails:
In order to achieve these goals, the design and management of urban systems need to be guided by urban sustainability principles. These include environmental capacity, reversibility, resilience, efficiency and equity.
The capacity of the environment to provide resources and absorb emissions and waste imposes absolute limits on human activities. The principle of environmental capacity requires that cities are designed and managed in order to deliver basic environmental, social and economic services within the limits imposed by the natural environment. The concept of environmental capacity helps set the limits to the activities that a space can sustainably absorb. In ecology, carrying capacity is the maximum population size of any given species that a habitat can support indefinitely without permanently damaging the ecosystem upon which it is dependent. When applied to human systems, such limits are mediated by consumption patterns, technological development and lifestyles. In cities, this capacity applies to both the natural and built environments and the interactions between natural and human-made systems.
One important premise to the management of the urban environment is a view of cities as dynamic systems. Cities are continuously challenged by the need to adapt to new demands from changes in population and economic activities. The management of the urban environment needs to cope with such changes. The ability of cities to respond to these challenges without impairing environmental capacity is a measure of their vitality. Planning interventions in the urban environment should as much as possible be reversible. A crucial feature of the sustainable city is resilience. A resilient city is one able to respond and recover from external stresses.
Sustainable development is a much broader concept than environmental protection (CEC, 1994). Economic and social dimensions need to be integrated with the ecological dimension of urban systems. Two other notions relevant to urban sustainability are efficiency and equity. The efficiency principle requires getting the maximum economic benefit for each unit of resources used (environmental efficiency) and the greatest human benefit from each unit of economic activity (welfare efficiency). Equal access for urban inhabitants to resources and services (equity) is important to modify unsustainable behaviour exacerbated by inequitable distribution of wealth.
The stated objectives imply that a broad definition of urban health is adopted by urban planning and management. Cities are integrated systems that facilitate the delivery of a wide range of services and activities (Brugmann, 1992). Every service that is delivered in urban systems is dependent upon the productive capacity and the efficient management of many subsystems. A systems approach can help understand and manage the complex relationships that take place in cities.
To date, there is no such universally accepted definition of urban health that brings together all the significant aspects of urban life, nor such an approach that describes the relationships between urban life and the state of the urban environment. Different approaches focus on specific components of the urban environment, such as the air, land and water, or on the various functions of urban systems, such as housing, water and energy supply, or transport. In the same way, responses to environmental problems in urban areas have focused for a long time on the various symptoms, and problems have been dealt with in a compartmentalised fashion, often reflecting the structure of local authorities. Today, many European cities recognise that moving towards a sustainable city requires an integrated approach.
STRATEGIES |
European cities have adopted various environmental strategies and pollution control measures to improve the urban environment. There is a wide range of planning and management options that can be classified under five main categories (Table 37.1): urban planning; urban management; economic instruments; standards; and public information.These are examined in a recent report on 'Sustainable Cities' prepared for the European Commission by the expert group on the urban environment (CEC, 1994).
This report stresses that there is no single set of actions which can apply equally to all European cities. Cities experience environmental problems in relation to their geographical profiles, demographic trends and economic assets. Cultural differences are also important determinants of the way people perceive urban problems. In addition, the organisational basis for implementing measures aiming at improving the urban environment varies between European countries according to the degree of decentralisation of competence and responsibilities. Nevertheless, a common European framework is important to identify and assess a broad range of options to operationalise sustainable development in urban areas.
The extent of the interrelationships within the urban system demonstrates the potential danger of ad hoc decision-making: the solution to one problem is often the cause of another. Effective management of urban air quality requires a strategy based on an overview of the urban system, with integrated decision-making in key areas. Few cities possess an administrative structure that can ensure such integration, most critically between landuse and transportation planning. While the city is the main focus of economic activity and the associated pressures on the environment, it cannot be analysed in isolation from the region within which it is located.
The range of actions of a European approach to urban areas is laid down in the Green Paper on the Urban Environment developed by the European Commission in 1990 (CEC, 1990). Two major areas of actions are identified: policies which relate to the physical structure of cities (landuse, mobility, green areas and historical heritage); and policies which relate to reducing the impact of urban activities on the environment (energy, water and waste management). An important step forward in this direction is taken by the policy report 'Sustainable Cities' (CEC, 1994) which followed the publication of the Green Paper. The report explores the application of sustainable development in urban areas and strongly recommends a systems approach to achieve integration across the policy areas emphasised by the EC's Fifth Environmental Action Programme.
In the light of these recommendations, the following five strategic levels can be considered.
Sustainable urban planning |
At the planning level, principles of urban sustainable design can be applied to urban landuse. A wide range of options can be considered to incorporate environmental considerations into urban planning, focusing on:
The scope for integrating environmental considerations into the design and management of urban systems varies in cities depending on their different planning systems. European cities have common objectives and targets as well as sets of procedures to influence the urban form and promote a balanced use of built-up and open areas.
Integrated transport management |
Improved environmental quality in cities can be achieved by integrated transport strategies aimed at reducing the impact of urban traffic and the overall amount of fuel consumed by transportation. A wide range of measures are available in order to:
These measures include:
Efficient management of urban flows |
Urban design and renewal projects need to be oriented towards reducing the use of water, energy and materials. This can be achieved through the implementation of low-impact technologies and the rational allocation of resources. Reducing energy consumption in urban areas requires energy efficiency and energy conservation measures. Energy efficiency refers to measures aimed at improving the efficiency of energy transformation processes through technological improvements, switches in technology and maintenance programmes. Energy conservation includes measures to improve the efficiency of end use and the rational allocation of energy sources. The visibility of ecotechnological solutions is particularly important for its high information value.
Targets and standards-setting |
Achieving better urban environmental quality requires setting targets and implementing systematic monitoring to ensure that environmental quality standards and the objectives established by the international conventions are met in urban areas. This can be achieved by adopting add-on technologies for specific pollution sources or by measures aimed at preventing pollution at source (1, 2, 3 above). Environmental standards aim to protect human health as well as ecological health. Air quality standards established by national authorities or international bodies set both limit values (critical for human health) and guide values values set as the objective for environmental improvement to prevent any long-term impact on health and the quality of life. Although lists of air quality guidelines published by WHO (WHO, 1987) or the EC (eg, 80/779/EEC) are already relatively extensive, there are many other chemicals in the air we breathe which pose a potential health hazard. Synergistic effects between compounds may also complicate the task of setting sound and safe guideline values (see also Chapter 38).
Urban environmental information |
The collection of consistent information on urban environmental quality and the pressure of urban activities on the regional and global environment is required to establish clear relationships between changes in the state of the urban environment and patterns of urban development. The environmental performance of urban areas needs to be monitored through a consistent set of urban environmental indicators to provide guidance in formulating and implementing urban environmental policies. Public information strategies are also important to provide the general public with immediate feedback on the state of the urban environment and the environmental effects of their actions. Information strategies include: public information systems, pollution alert systems and local environmental reporting.
Urban environmental stress is an increasing concern for the majority of European people. The importance of urban environmental problems in Europe is emphasised by the numerous links that can be made with almost all problems treated in the present report. Cities share an important role in achieving sustainable development. European cities are therefore challenged with an important responsibility. The Charter of European Cities and Towns Towards Sustainability adopted at Aalborg (Denmark, 27 May 1994) recognises this and provides the basis to implement the Local Agenda 21 process (Box 37B) in order to meet the mandate of the UN Conference on Development and the Environment (UNCED, 1992).