The Human Population Miss Napolitano & Mrs. Rodriguez Environmental Science

The Human Population Over Time  Demography : the study of human populations  Includes size, makeup, & growth  Developed countries : higher average incomes, slower population growth, diverse industrial economies  Developing countries: lower average incomes, agriculture- based economies, & rapid population growth

The Human Population Over Time  Human population began to grow rapidly in 1800s  Growing exponentially – growth rates increased during each decade  Growth rate due to increases in food production & hygiene  Unlikely to be able to sustain current growth rate for much longer

Age Structure  Age structure: distribution of ages in a specific population at a certain time  Ex: population has more young people  population size will increase  Graphed in a population pyramid  High growth rates have more young people  Slow/no growth rates have even distribution  Fewer young people when parents have fewer children

Age Structure Diagrams

Survivorship  Survivorship: percentage of members of a group that are likely to survive at any given age  Notes when members of a population die  Type I: more people survive to old age  Developed countries  Type II: similar death rate at all ages  Type III: many children die young  Developing countries

Fertility Rates  Fertility rate: number of babies born each year per 1,000 women  Total fertility rate : average number of children a woman gives birth to in her lifetime  Replacement level: average number of children each parent must have in order to “replace” themselves  ~2.1 because not all born will survive to reproduce  Fertility level of US dropped below replacement level for first time in 1972

Migration  Migration : movement of individuals between areas  Emigration: movement out of an area  Immigration : movement into an area  Populations might be decreasing if not for immigration in many developed countries

Life Expectancy  Death rates have declined drastically due to access to adequate food, clean water, safe sewage disposal, & vaccines  Life expectancy: average number of years a person is likely to live  Affected by infant mortality (death rate of infants)  Average life expectancy around the world is ~67 years  Increased to almost 80 in developed countries  More people means more diseases like HIV and TB 

The Demographic Transition  Demographic transition : describes how populations have stopped growing in developed countries  Industrial development causes economic and social progress that then affects population growth rates

4 Stages of Transition  Stage 1 :Birth & death rates both high, population stable  Stage 2 : Population explosion  Hygiene, nutrition & education improve, leading to lower death rates  Stage 3 : Population slows & starts to stabilize  Due to birth rate decrease  Stage 4 : Birth rate drops below replacement level  Population starts to decrease

Problems of Rapid Growth  Shortage of fuel wood  Unable to boil water & cook food in many countries  Unsafe water  Drinking, washing, sewage disposal  Causes diseases & parasites  Negative impacts on land  Shortage of land for crops, housing, or natural habitats  Causes urbanization (moving to cities) or suburban sprawl ( cities become crowded, move to suburbs)

Demographically Diverse World  Not all countries fit the terms “developed” or “developing”  Some mix between the two – ex: modern industries with low incomes  Focus is on least developed countries  Few signs of development, increasing death rates, high birth rates  Populations are relatively stable in Europe, the US, Canada, Russia, South Korea, Thailand, China, Japan, Australia, & New Zealand  Populations growing rapidly in less developed regions (mostly in Asia)

Managing Population Growth  Some governments tried to reduce birth rates  China, Thailand, & India created campaigns to reduce fertility rates of citizens  Campaigns include advertising, family planning, economic incentives, or legal punishments  Currently, fertility rates have declined since 1970  Rates still higher in less developed regions  UN projects population will be between 8 billion & 11 billion by 2050, depending on fertility rates