02.0D BIO Communities & Ecosystem Dynamics - Human Population Growth (PART D)

Thomas Malthus

English Economist who believed that only war, famine, and disease could limit human population growth.
He also thought that human populations would be regulated by competition (war), limiting resources (famine), parasitism (disease), and other density-dependent factors.

Demography

The scientific study of human populations that examines characteristics of human populations and attempts to explain how those populations will change over time.

Demographic Transition

A dramatic change in a society's population from high birthrates and death rates to low birthrates and death rates.

Developed Countries

Countries that:
- Have low fertility rates
- Makeup 16% of world's population
- Use 80% of world's wealth
- Have 10-15% of the population in poverty
- Eat high on the food chain
- Fertility Rate < 2
- Negatively impact the environment due to affluence and technology
- Have a high % of older people

Developing Countries

Countries that:
- Have High fertility rates
- Makeup 84% of world's population
- Use 20% of world's wealth
- Have 45 % of population in poverty
- Have a large number of people that are malnourished
- Have a Fertility rate > 2
- Negatively impact the environment due to large population size
- Have a high % of younger people

Age- Structure Diagrams

Diagrams that show the population of a country broken down by gender and age group. Used by demographers to predict needs.

Consequences of Large Population

Deforestation, loss of agriculture, resource depletion, less biodiversity, more pollution

Factors that controlled early human population growth

Food was hard to find. Predators and diseases were common and life-threatening.

Factors that contributed to decreased human death rates

Improved nutrition, sanitation, medicine, and healthcare.

Demographic Transition (Stage I)

Birth rates and death rates are both high. In the U.S. this stage occurred prior to the industrial revolution.

Demographic Transition (Stage II)

Advances in nutrition, sanitation, and medicine lead to lower death rates. Birthrates remain high for a time, so births greatly exceed deaths and the population increases exponentially.

Demographic Transition (Stage III)

As the level of education and living standards rise, families have fewer children and the birthrate falls; population growth slows.

Demographic Transition (Completed)

Birthrate meets the death rate, and population growth stops.

Population pyramid

Another name for an age-structure diagram.

Future Population Growth

Current data suggest that global human population will grow more slowly over the next 50 years than it grew over the last 50 years. Because the growth rate will still be higher than zero in 2050, our population will continue to grow.