More than one half of the world population lives in cities, and every country of the world is becoming increasingly urbanized. Urbanization—the gradual shift in residence of the human population from rural to urban areas—combined with overall growth of the world’s population could add another 2.5 billion people to urban areas by 2050. Close to 90% of this increase will take place in Asia and Africa, according to the United Nations. This trend is changing the landscape of human settlement, with significant implications for living conditions, the environment, and development.
As the world continues to urbanize, sustainable development depends increasingly on the successful management of urban growth. Many countries face challenges in meeting the needs of their growing urban populations, including housing, transportation, energy systems, and other infrastructure (e.g., water, sanitation, electricity, roads), as well as employment and basic services such as education and health care. Integrated policies to improve the lives of both urban and rural dwellers are needed, while strengthening the linkages between urban and rural areas, building on their existing economic, social, and environmental ties.