Description:
By concentrating people, cities concentrate consumption of resources and materials. The IES calls for the city’s renewable and non-renewable resources to be sourced, allocated, managed and recycled responsibly and equitably, and without adversely affecting human health or the resilience of ecosystems. Resources and materials should also be primarily sourced from within the bioregion (www.ecocitystandards.org).

The ecological footprint of high-income/high-consuming cities is approximately 200 times their physical area (Rees 1996). This means the amount of land required to produce the resources consumed is 200 times greater than the physical space the city occupies. If one excludes food and energy from this estimate, the resources needed to produce consumer goods along with the materials used to construct the city requires an ecosystem area approximately 43 times the city’s physical area, with half the demand attributed to consumables and half to construction (Rees and Moore 2013). The latter may seem surprisingly low considering how much materials are used to build cities. However, it is important to consider the duration of the materials’ life once incorporated in the built environment. Whereas most goods are consumed and discarded within the year, the buildings and infrastructure of the city typically last 50 to 75 years, if not longer.

To achieve the IES principle of responsible resources/materials use requires a focus on both the type and amount of goods we consume as well as the way we build and maintain our cities. Manufacturing processes associated with production of just four products: paper, plastics, chemicals and metals, account for 71% of USA toxic emissions (Young and Sachs, 1994). Paper and metal products enjoy high recycle rates in many industrialized economies, but the process remains energy intensive, and some products such as plastics can only be down-cycled not recycled. This means that decisions about what we consume and the durability and capacity for reuse of what we consume are important. Decisions about what materials to use in city-building are also important from both the perspective of the functioning of the city and its impact on local and global ecosystems. For example, local governments in high-income cities are typically the largest users of concrete for municipal infrastructure, including roads and sidewalks. For every tonne of concrete produced, one tonne of greenhouse gas emissions is also produced as part of the cement manufacturing process.

Sustainable cities use materials responsibly. This means building durable cities that allow for flexible use and reconfiguration of space. It also means avoiding materials with toxic substances. Cities that make use of locally available materials reduce the need for importing foreign substances and support locally appropriate building technologies that enable people to access materials to construct their own residences. Appropriate technologies that match supply of materials to demand for services is also an important strategy. For example, not all urban surfaces need to be paved. Maximizing green spaces and using alternatives such as pebbles to line heavily trodden paths can provide similar surface integrity to concrete.

References:
Rees, W.E. 1996. Revisiting Carrying Capacity: Area-Based Indicators of Sustainability, Population and Environment, Vol. 17, No. 3.
Rees, W.E. and J. Moore. 2013. Ecological Footprints, Fair Earth-Shares and Urbanization, Chapter 1 in Robert Vale and Brenda Vale, eds., Living within a Fair Share Ecological Footprint. London: Earthscan.
Young, J. and A. Sachs. 1994. The Next Efficiency Revolution: Creating a Sustainable Materials Economy. Worldwatch Paper 121. Washington DC: Worldwatch Institute (http:// www.worldwatch.org/bookstore/publication/worldwatch-paper-121-next-efficiency- revolution-creating-sustainable-materials).

Rationale:
It would be unrealistic to assume that some materials, steel for example, could be reused in the city but that it seemed reasonable to assume that everything can be reused within 2000 km of a city. The lower bar for the ecoregion assumes that it would be preferable but more difficult to reuse all materials within a bioregion.)