Urban systems

Context

Today, 72% of the total population of the European Union (EU) live in cities, towns and suburbs.^[1] The environmental dimension of urban living is crucial for the health and well-being of their residents as well as the quality of the surrounding territories.^[2] The 'Urban Audit'^[3] data base and the 'Urban Atlas'^[4] provide detailed information on major urban areas.

Figure 1: The urban system

Various concepts have been coined to describe how complex interactions can impact on urban living (Figure 1).

• The 'urban metabolism' refers to the flows necessary to satisfy the needs of those living in cities.
• 'Grey infrastructure', such as roads, metros, railways, buildings and utilities, determines a city's layout. Yet without integrated urban planning, this urban 'engineering' generates soil sealing, fragments natural systems, increases mobility and associated pollution, energy and material consumption.^[5][6]
• 'Green infrastructure' is a way to work with nature to provide social, ecological and economic benefits to the urban population such as air filtration, temperature regulation, noise reduction, flood protection and recreational areas.^{[7][8][9][10]}

The high concentration of people and economic activities in cities cause environmental pressures. Yet cities can be planned, designed, managed and governed in an increasingly efficient way.

The EU has had a substantial impact on the development of cities over recent decades through its cohesion policy and sectoral policies (e.g. water, waste, noise, air). The Thematic Strategy on the Urban Environment^[11] and the recent 7th Environment Action Programme (7th EAP)^[12] promote integrated urban policy.

This could also apply for the principles of urban development in the EU as expressed in its 'Territorial Agenda of the European Union 2020'.^[13] An intergovernmental process, coupled with the practical experiences gained through the European Regional Development Fund (ERDF), has led to clear principles of urban development. This is known as the acquis urbain.^[14]

Key trends

Figure 2: Urban sprawl by country and within countries (2009)^[15]

Cities depend on their neighbouring areas for supply and disposal services. The densification of urban areas is viewed as a way to reduce their spatial growth and the associated environmental impacts.

Urban sprawl versus urban density: Between 2000 and 2006 about 1 000 km² of land^[16] was covered every year by artificial surfaces.^[17] Re-using land (e.g. rehabilitating industrial sites or contaminated land), which had previously been developed but is currently not in active use, is a way to further reduce land take. Around 2.5% of the increase in artificial surfaces^[18] created between 1990 and 2000 came about through the recycling of already developed land.^[19] 

Typically, European cities are dense but they are becoming less dense at their boundaries. Emissions of greenhouse gases (GHG) are higher in commuter towns not only because of car dependency but also due to the characteristics of the buildings. This is because high energy housing, such as detached and semi-detached dwellings, is dominant.^[20] Nevertheless some European urban areas continue to expand. There are large differences in the level of sprawl both between and within European countries (Figure 2).^[21] The more areas are built up and the lower their intensity of use, the higher the degree of urban sprawl.

The challenges of health and well-being: Up to one third of Europeans living in cities are exposed to levels of air pollutants^[22] exceeding EU air quality standards, in particular for particulate matter (PM) and ozone (O₃),^[23][24] road transport being a significant source. Half of the EU's urban population is exposed to traffic noise levels above 55dB.^[25] In the dense urban environment green spaces, correctly planned and managed, can contribute to improve the air quality and to reduce excessive heat.^[7][10][26]

Resource-efficient cities: Total municipal solid waste has decreased by 2% between 2004 and 2012. Significant progress has been made in recycling glass, paper, cardboard, metals and plastic.^[27] Thanks to better municipal waste management, life-cycle GHG emissions from municipal waste were cut by 57 million tonnes CO₂-equivalent during the period 1990-2012.

Urbanisation leads to an increase in land take and soil sealing. This permanent covering by impermeable artificial material, such as asphalt and concrete, affects, inter alia, food production, water absorption and filtration.^[5]

Cities need adequate amounts of water. They compete with agriculture, industry and tourism and this situation will be exacerbated with climate change. The largest cities are already transporting water over distances ranging from 100-200 km.

Cities emit 69% of Europe's CO₂.^[28] It is critical for cities to reduce GHG emissions and to enhance resilience to potential impacts from climate change.

Prospects

The role of cities is critical in a transition towards a low carbon, resource-efficient and ecosystem-resilient society.^[29] The cities of tomorrow have the potential to be healthier, denser, greener and smarter through better urban planning and governance.

Adapt to climate change now and at lower cost: Climate change will expose cities to more frequent and prolonged heatwaves, flooding, water scarcity and forest fires.^[26] Cities need to build climate change resilience through strong local and regional planning and investments to maintain the functioning of urban infrastructure and services (such as buildings, roads, railways, energy grids and sewage systems) and develop green infrastructure. The European Climate Adaptation Platform, Climate ADAPT^[32], launched by the European Commission's Directorate General for Climate Action (DG CLIMA), aims to support countries in adapting to climate change.

Modernising 'grey' infrastructure: Without renovation and restructuring, infrastructure that sustains everyday life — related to energy and water supply, waste management, housing and transport systems — can lead to overuse of resources and energy.^[33]

Smart urban design influences transport demand. Local authorities can encourage the use of sustainable forms of transport by providing efficient, reliable and affordable collective transport and convenient walking and cycling infrastructure.^[34]

Developing multifunctional green infrastructure: Cities are dependent on ecosystems inside as well as outside the city's limits. In built-up cities green spaces, from trees to large parks, improve the health and well-being of residents. Green infrastructure is seen as a cost-effective and efficient tool to combat the impacts of the climate change, to build disaster resilience and to deliver health-related benefits.^[8][9][10]

Smarter cities: Smart technologies and services, that often rely on information and communication technology, offer huge opportunities to make urban environments cleaner and healthier to live in. Eco-innovations^[35] can be used in many domains such as recycling, monitoring, renewable energy, transport, etc.^[36][37]

Engaging society: The transition to urban sustainability requires behavioural changes that need to be accepted by society. Municipalities can raise citizens' awareness, generate fruitful participation and support citizen initiatives such as car-sharing, urban gardening and collaborative consumption initiatives. It is now possible to empower citizens and generate communities through ICT-enabled solutions.