Abstract
The exponential growth of the global human population during the 20th century was perhaps our most profound impact on Earth since the dawn of civilization. The 21st century, on the other hand, is already characterized by slowing population growth, negative growth in some countries, and the prospect of global population stabilization by 2100. This chapter summarizes the population history, trends, and policies that led to a world of 8 billion humans; the causes and consequences of demographic change around the world; and visions of achieving population stabilization.