How Zero Population Growth Works

Causes and Effects of Overpopulation

Over the past 110 years – a blink of the eye in human history – the world population has exploded from 1.6 billion to 7.2 billion [source: Graf and Bremner]. This exponential growth has many causes, most of them positive and directly related to improvements in health care [sources: CDC, Wattenberg, WHO]:

  • Global life expectancy increased from an average of 31 years in 1900 to 70 in 2012.
  • The global infant mortality rate in 1900 was 165 deaths per 1,000 live births; in 2013 it was 34 deaths per 1,000 live births.

Still, the vast gains humanity has made in terms of health, economic security and human rights have not been distributed equally among the world's 7.2 billion inhabitants [sources: FAO, UN]:

  • An estimated 1.4 billion people worldwide in 2010 lived on less than $1.25 a day, down from 1.8 billion in 1990.
  • Worldwide, an estimated 805 million people went to bed hungry every night in 2014, more than half of them living in Asia.
  • One in four people in sub-Saharan Africa in 2014 was chronically malnourished.

Global population growth also puts a strain on natural resources like clean water and forests [sources: WHO, WWF].

  • In 2014, 750 million people worldwide lacked access to clean water, contributing to 842,000 deaths each year from diarrhea-related illnesses
  • Millions of hectares of forest and jungle are cleared each year for increased agricultural production to feed soaring demand for soybeans, palm oil and grazing land for beef cattle

In 2014, more than half of the world's population lived in cities [source: UN]. While cities can provide improved economic opportunities for people in developing countries, they are also home to slums and sweatshops. In the poorest nations, more than half of city-dwellers live in slums with limited or no access to clean water, sanitation or permanent shelter, let alone education or health care. In sub-Saharan Africa, 61.7 percent of the urban population lives in slums. The United Nations predicts that almost all of future population growth will happen in cities.

Even if Ehrlich's original predictions were wrong, there are clearly regions of the world in which too many people are struggling to survive on too few resources. Next we'll look at some of the solutions to overpopulation proposed by the zero population growth movement.