Human Population Human Population GrowthGrowthChristina HullChristina Hull

210 The Dynamic Earth210 The Dynamic Earth

Dr. Michael SandyDr. Michael Sandy

Present Population StatusPresent Population Status

In 2000, the world had 6.1 billion human In 2000, the world had 6.1 billion human inhabitants. inhabitants.

In the last 50 years, world population multiplied In the last 50 years, world population multiplied more rapidly than ever before, especially in more rapidly than ever before, especially in underdeveloped and poverty-stricken countries. underdeveloped and poverty-stricken countries.

FertilityFertility The current growth of population is driven by fertility.  The current growth of population is driven by fertility.  Fertility is largely controlled by economics and by human Fertility is largely controlled by economics and by human

aspirations. aspirations. The high fertility of a developing world can be partially explained by The high fertility of a developing world can be partially explained by

the large number of hands needed to perform low-technology the large number of hands needed to perform low-technology agricultural tasks. In these areas, families with large numbers of agricultural tasks. In these areas, families with large numbers of children realize an enhanced economic status. children realize an enhanced economic status.

As technology improves, parents realize that having more children As technology improves, parents realize that having more children decreases rather than increases their standard of living. decreases rather than increases their standard of living.

MortalityMortality In the developing world, the death rate has dropped, more or less In the developing world, the death rate has dropped, more or less

continuously, since the start of the industrial revolution. continuously, since the start of the industrial revolution. Personal hygiene and improved methods of sanitation have played a major Personal hygiene and improved methods of sanitation have played a major

role and preceded the impact of modern medicine and, in particular, the role and preceded the impact of modern medicine and, in particular, the development of antibiotics capable of reducing death due to infection. development of antibiotics capable of reducing death due to infection.

The combination of decreasing death rate due to the march of progress in The combination of decreasing death rate due to the march of progress in sanitation and medicine, along with the fluctuating birth rate due to sanitation and medicine, along with the fluctuating birth rate due to economic changes, has led to a profound change in the population growth economic changes, has led to a profound change in the population growth curve in the developed world. This change is called the Demographic curve in the developed world. This change is called the Demographic Transition.Transition.

The Demographic TransitionThe Demographic Transition Stage 1: Birth rates and death rates are both high. No demographic Stage 1: Birth rates and death rates are both high. No demographic

transition has occurred. transition has occurred.

Stage 2: Standards of hygiene and more modern medical techniques began Stage 2: Standards of hygiene and more modern medical techniques began to drive the death rate down, leading to a significant upward trend in to drive the death rate down, leading to a significant upward trend in population size. The birth rate remained high, as much of the economy was population size. The birth rate remained high, as much of the economy was based on agriculture. based on agriculture.

Stage 3: Urbanization actively discouraged from having large families. In Stage 3: Urbanization actively discouraged from having large families. In response to these economic pressures, the birth rate started to drop, response to these economic pressures, the birth rate started to drop, ultimately coming close to the death rate.ultimately coming close to the death rate.

Stage 4. The last stage of the demographic transition in Europe was Stage 4. The last stage of the demographic transition in Europe was

characterized by a higher, but stable, population size. Birth and death rates characterized by a higher, but stable, population size. Birth and death rates were both relatively low and the standard of living became much higher were both relatively low and the standard of living became much higher than during the earlier periods. The developed world remains in the fourth than during the earlier periods. The developed world remains in the fourth stage of its demographic transition.stage of its demographic transition.

The Demographic TransitionThe Demographic Transition

The Demographic TransitionThe Demographic Transition

Projected World Population GrowthProjected World Population Growth

Future Global Population GrowthFuture Global Population Growth

An eventual world population of 8-12 billion is expected by An eventual world population of 8-12 billion is expected by the end of the century.  the end of the century. 

According to a report from the United Nations Population According to a report from the United Nations Population Fund, based on 1998 analyses, projections for the future Fund, based on 1998 analyses, projections for the future global population are being revised downward.  The global population are being revised downward.  The projection for 2050 now is 8.9 billion, substantially lower projection for 2050 now is 8.9 billion, substantially lower than the 1996 projection of 9.4 billion.  than the 1996 projection of 9.4 billion. 

The major reason for the lower projection is good news: The major reason for the lower projection is good news: global fertility rates have declined more rapidly than global fertility rates have declined more rapidly than expected, as health care, including reproductive health, has expected, as health care, including reproductive health, has improved faster than anticipated, and men and women improved faster than anticipated, and men and women have chosen to have smaller families.  have chosen to have smaller families. 

About one-third of the reduction, however, is due to About one-third of the reduction, however, is due to increasing mortality rates in sub-Saharan Africa and parts increasing mortality rates in sub-Saharan Africa and parts of the Indian subcontinent. The most important factor is of the Indian subcontinent. The most important factor is HIV/AIDS, which is spreading much faster than previously HIV/AIDS, which is spreading much faster than previously anticipated. anticipated.

Future Global Population GrowthFuture Global Population Growth

Is There Carrying Capacity For Is There Carrying Capacity For Human Beings?Human Beings?

Such growth cannot continue. If it does, every Such growth cannot continue. If it does, every square foot of the Earth's surface will be taken up square foot of the Earth's surface will be taken up by a human within the next few hundred years. by a human within the next few hundred years.

Experience with other species tells us that Experience with other species tells us that resource limitations and/or habitat degradation resource limitations and/or habitat degradation will force the human population curves to will force the human population curves to approach an upper limit, or the carrying capacity.approach an upper limit, or the carrying capacity.

What Can Be Done?What Can Be Done?

Increase human productive capacities Increase human productive capacities through technology and innovation through technology and innovation

Reduce numbers and expectations of Reduce numbers and expectations of people through such means as family people through such means as family planning and vegetarian diets planning and vegetarian diets

Change the terms of people’s interactions Change the terms of people’s interactions through improved planning and through improved planning and government to enhance social justice.government to enhance social justice.

ReferencesReferences

http://www.globalchange.umich.edu/http://www.globalchange.umich.edu/globalchange2/current/lectures/humaglobalchange2/current/lectures/human_pop/human_pop.htmln_pop/human_pop.html

http://www.prb.org/Content/Navigatiohttp://www.prb.org/Content/NavigationMenu/PRB/Educators/Human_PopulanMenu/PRB/Educators/Human_Population/Population_Growth/Population_Gtion/Population_Growth/Population_Growth.htmrowth.htm