Population Population is viewed by many as the driver of global environmental change. Even if the rate of growth is constant, the number of people added over each year or time interval increases as the population becomes larger. Only by slowing the rate of population growth, until eventually the growth rate is zero, can population be stabilized. An examination of global patterns in population serves as a useful reminder that global averages, as important as they are, tell only a fraction of the story. Regional and local patterns are extremely important.
Human population has many direct and indirect effects on other variables.
Two that are very directly connected are urbanization and disease. The world's population is quickly becoming urbanized as people migrate from rural to urban areas, in search of a better life and better future for their children. Such is the pull of perceived opportunity , however, that urban growth continues unchecked. Disease spreads more readily under crowded conditions, where sanitation is lacking or overwhelmed by urban growth, and where individual health faces additional challenges from an inadequate food supply, air pollution,etc. Some of the most important are old enemies diarrheal diseases, tuberculosis , malaria , cholera .