A Changing Human Population Environmental Science

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

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

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

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

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

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

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

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 have access to adequate food, clean water, safe sewage disposal, medicine/health care.  The discovery of vaccines in the 20th century also contributed to the declining death rates.

Life Expectancy The average number of years that a member of a population is likely to live 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 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. Better medical care has lead to higher life expectancy in developed and developing nations.

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.

Women and Fertility  A decline in birth rates can most clearly be related to increasing education and economic independence for women (jobs).  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.  Educated women delay child bearing.