3.2.3.8 - Sustainable cities, footprints and liveability

Local impacts and global ecological footprints

Cities concentrate consumption and production but draw resources from, and export impacts to, places far beyond their boundaries.

Locally, development changes habitat, drainage, air quality, noise and land values. Globally, imported food, fuel, construction materials and manufactured goods require land, water and energy elsewhere. Supply chains create embodied environmental impacts even when the city contains little manufacturing. Urban carbon emissions contribute to climate change; waste trade can transfer exposure.

A global hectare is standardised to world-average biological productivity. It is not the city's physical area, and an ecological footprint is not the same as tonnes of CO₂ equivalent. Consumption accounting includes imports and attributes appropriate exported production elsewhere. Different methods and years cannot be treated as a simple trend.

The London Sustainable Development Commission's 2005 quality-of-life report reported a Greater London footprint for 2000 of about 49 million gha, or 6.63 gha per person, citing the City Limits study. This historical major-city estimate demonstrates the large external resource area supporting urban consumption. It is not a current Salford or Detroit value. Total and per-person footprints answer different questions: a large city can have a high total but a lower per-person demand than a smaller, more car-dependent settlement.

Source: LSDC quality-of-life report, 2005.

Natural, physical, social and economic sustainability

Urban sustainability means maintaining environmental systems and a viable, fair urban life through time.

Natural sustainability protects biodiversity, water quality and ecological processes within and beyond the city. Physical sustainability provides durable housing, drainage, energy and transport infrastructure that can adapt to hazards. Social sustainability includes health, safety, inclusion, participation and access to affordable services. Economic sustainability requires viable employment, resources for maintenance and resilience to shocks. A strategy can improve one dimension while harming another.