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Human Population

Discusses past and future human population growth.

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Too many people?

In October 2011, the human population passed 7 billion people. What problems could result if the human population continues its rapid rise? One issue is that overpopulation makes many environmental issues more serious. More people on the planet means more food and water is needed and more pollution is generated. Is there a carrying capacity for the human population?

Human Population

How quickly is the human population growing? If we look at worldwide human population growth from 10,000 BCE through today, our growth looks like exponential growth. It increased very slowly at first, but later grew faster and faster as the population increased in size (Figure below). And recently, the human population has increased at a faster pace than ever before. It has taken only 12 years for the world's population to increase from six billion to seven billion. Considering that in the year 1804, there were just one billion people, and in 1927, there were just two billion people, the recent increase in the human population growth rate is characteristic of exponential growth. Does this mean there are unlimited resources?

Worldwide human population growth from 10,000 BCE through today.

Five Stages

On the other hand, if you look at human population growth in specific countries, you may see a different pattern. On the level of a country, the history of human population growth can be divided into five stages, as described in Table below. Some countries have very high birth rates, in some countries the growth rate has stabilized, and in some countries the growth rate is in decline.

Stage Description
1 Birth and death rates are high and population growth is stable. This occurred in early human history.
2 Significant drop in death rate, resulting in exponential growth. This occurred in 18th and 19th century Europe.
3 Population size continues to grow.
4 Birth rates equal death rates and populations become stable.
5 Total population size may level off.

The United Nations and the U.S. Census Bureau predict that by 2050, the Earth will be populated by 9.4 billion people. Other estimates predict 10 to 11 billion.

Future Growth

There are two different beliefs about what type of growth the human population will undergo in the future:

  1. Neo-Malthusians believe that human population growth cannot continue without destroying the environment, and maybe humans themselves.
  2. Cornucopians believe that the Earth can give humans a limitless amount of resources. They also believe that technology can solve problems caused by limited resources, such as lack of food.

The Cornucopians believe that a larger population is good for technology and innovation. The 5-stage model above predicts that when all countries are industrialized, the human population will eventually level out. But many scientists and other Neo-Malthusians believe that humans have already gone over the Earth’s carrying capacity. That means, we may have already reached the maximum population size that can be supported, without destroying our resources and habitat. If this is true, then human overpopulation will lead to a lack of food and other resources. Overpopulation may also lead to increased disease, and/or war. These problems may cause the population of humans to crash. If these issues are not controlled, could the human population go extinct?

Which of the above theories makes sense to you? Why?


  • carrying capacity: Maximum population size that can be supported in a particular area without destroying the habitat.
  • Cornucopians: Believe that the Earth can give humans a limitless amount of resources; also believe that technology can solve problems caused by limited resources.
  • exponential growth: Pattern of population growth in which a population starts out growing slowly but grows faster and faster as the population size increases.
  • Neo-Malthusians: Believe that human population growth cannot continue without destroying the environment, and maybe humans themselves.


  • The human population is undergoing exponential growth.
  • Future outlooks on human population growth differ; some think we will have a limitless amount of resources, while others think we have already reached our carrying capacity.


Use the resource below to answer the questions that follow.

  1. How much land is the USA is lost to urban sprawl every year? Can you think of any way to alter this situation without stopping or limiting population growth?
  2. How has land use around Phoenix, Arizona, USA changed since 1912?
  3. How did urban areas change after agricultural expansion in Arizona? Can you think of any way these changes could have occurred in reverse order?
  4. How does urban growth affect water usage? What problems does this present for the sustainability of urban environments?


  1. Describe the rate of human population growth.
  2. How do the Cornucopians and Neo-Malthusians differ in their viewpoints?

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