Urbanisation

Urbanisation replaces open land with buildings, roads and other infrastructure. Buildings add weight to cliffs, which can contribute to instability. Roads and tarmac alter drainage patterns: water runs off hard surfaces rather than soaking into the ground beneath them.

These changes help explain three connected outcomes: changing fertility and death rates, increasing urbanisation, and differences between more prosperous and less developed regions. Growth does not reach every place equally, so improving national conditions can coexist with large regional inequalities.

Urbanisation means an increase in the percentage of a country's population living in urban areas. These are connected, but they are not identical: an urban population can grow without its share of the national population increasing, if the rural population grows just as quickly.