Cities: Managing Densely Settled Social-Ecological Systems

Abstract

The transition from a rural to urban population represents a demographic, economic, cultural, and environmental tipping point. In 1800, about 3% of the world’s human population lived in urban areas. By 1900, this proportion rose to approximately 14% and now exceeds 50% in 2008. Nearly every week 1.3 million additional people arrive in the world’s cities (about 70 million a year), with increases due to migration being largest in developing countries (Brand 2006, Chan 2007). People in developing countries have relocated from the countryside to towns and cities of every size during the past 50 years. The urban population on a global basis is projected by the UN to climb to 61% by 2030 and eventually reach a dynamic equilibrium of approximately 80% urban to 20% rural dwellers that will persist for the foreseeable future (Brand 2006, Johnson 2006). This change from 3% urban population to the projected 80% urban is a massive change in the social-ecological dynamics of the planet.