The Human Population

Miss Napolitano & Mrs. RodriguezEnvironmental 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