Since the 1950s, the world’s urban population has grown more than 400% to 3.9 billion today. About 60% of the total population is expected to live in urban areas by the year 2025. For the United States (U.S.), 80% of the population lives in urban areas. The Earth has entered into the Anthropocene, a new geological epoch dominated by urbanization and people.
Sun, Ge; Caldwell, Peter. 2015. Impacts of urbanization on stream water quantity and quality in the United States. Water Resources Impact, Volume 17 Number 1. 4 p.