The growth of urban centres also requires the building of communication and transport networks, with the demand for roads, bridges, railways etc rising. All this development requires raw materials. In particular, it requires steel to build the apartments in which the new city dwellers live and to build the infrastructure that supports those cities.
For example, a typical 90m2 apartment in China requires about six tonnes of steel, and 10km of metropolitan subway requires around 75,000 tonnes. On average, every tonne of steel that is produced requires around 1.7 tonnes of iron ore and over half a tonne of coking coal, and Australia is in the fortunate position of having ample low-cost, high-quality supplies of both.