A Changing Environment for Human Security

32  Sustainability and cities

Meeting the grand challenge for the twenty-first century

Peter J. Marcotullio and William D. Solecki

Introduction

Urbanization in the twenty-first century is approaching a tipping point. The scale of increase in urban population and the rate of urbanization are unprecedented, and we are in the midst of a dramatic transition that will impact economic, social and environmental conditions at all scales (UNFPA, 2007; United Nations 2010). All the promises and challenges associated with human development are now increasingly concentrated in cities.

The scope, extent, speed, and timing of contemporary urbanization, combined with the demands for resource efficiency, pollution reduction, social equity and cohesion, and economic ...