A population is the number of individuals of a given species, usually within a specified habitat or area. Within the science of ecology, the study of population dynamics, or the ways in which the number of individuals in a community expands and contracts, makes up an important subfield known as population biology. While ecologists and wildlife biologists rely on understanding the nature of population change and the factors that influence population size, one of the main ways population studies have been used is in projecting the growth of the human population. Since the 1960s human population growth has been an issue of fierce theoretical debate. Many scientists and social planners predict that the human population, like animal populations frequently observed in nature, is growing at a perilous rate that will ultimately lead to a catastrophic die-off in which billions of people will perish. Other scholars and...