1. A Changing Human Population
Environmental Science

2. Studying Human Populations
Demography – the study of the characteristics of populations (usually human populations)
Countries are divided into 2 categories by demographers:
Developed – higher average incomes, slower population growth, diverse industrial economies
Developing – lower average incomes, rapid population growth, agriculture-based economy

3. Forecasting Population Size
Demographers try to predict what will happen to a population in order to plan for future infrastructure and services
Demographers look at several different factors to make their predictions

4. Age Structure
Age structure describes the distribution of ages of a population
Countries with high growth rates have more young people than old people
Countries with slow growth or no growth have an even distribution of ages in the population

5. Survivorship
The percentage of members of a group that are likely to survive to a given age
To predict survivorship, demographers study a group of people born at the same time and notes when each member of the group dies.
Age

6. Fertility Rates
The number a babies born each year per 1000 women of childbearing age (15-44)
Replacement level – the average number of children parents must have to “replace” themselves

7. Declining Death Rates
Increased access to food, clean water, and safe sewage disposal have lead to a decrease in the world death rate
This decrease has more to do with the huge increase in the human population than the birth rate.

8. Migration
Migration in general, is any movement of individuals or populations from one location to another.
The populations of many developed countries might be decreasing if not for immigration.

9. Declining Death Rates
The dramatic increase in Earth’s human population in the last 200 years has happened because death rates have declined more rapidly than birth rates.
Death rates have declined mainly because more people now have access to adequate food, clean water, and safe sewage disposal.
The discovery of vaccines in the 20th century also contributed to the declining death rates.

10. Life Expectancy
The average number of years that a member of a population is likely to live
Infant mortality rates have the largest influence on life expectancy numbers
Better medical care has lead to higher life expectancy in developed and developing nations.

11. Demographic Transition
The demographic transition is the general pattern of demographic change from high birth and death rates to low birth and death rates.
Industrial development causes economic and social progress that then affects population growth rates.

12. Women and Fertility
A decline in birth rates can most clearly be related to increasing education and economic independence for women.
Educated women learn family planning techniques and find that they do not need to bear as many children to ensure that some will survive.
Women are able to increase the prosperity for their families while spending less energy bearing and caring for children.