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Human Population

Chapter 8

Environmental Science

Computer simulations predict the future

• If the world does not

change…

• population and production will suddenly decrease
• in a sustainable world…
• population levels off
• production and resources stabilize
• pollution declines

Population distribution

• Increased density impacts the environment, but

relieves pressure in less-populated areas

• Humans are unevenly distributed around the globe

Age structure affects future population size

• Having many individuals in young age groups (wide base)

results in high reproduction and rapid population growth

• Even age distribution: remains stable because births =

deaths

Sex ratios

• Naturally occurring sex ratios for humans

slightly favors males (100 females born to 106

males)

• In China, 120 boys were reported for 100 girls
  • cultural gender preferences…combined with the government’s one-child policy… - led to selective abortion of female fetuses
• Undesirable social consequences of many single

Chinese men

• teenage girls were kidnapped and sold as brides

Population growth depends on various

factors

• Whether a population grows, shrinks, or remains

stable depends on:

• rates of birth, death, and migration
  • birth and immigration add individuals
  • death and emigration remove individuals
• Technological advances led to dramatic decline in

human death rates

• widening the gap between birth rates and death rates resulting in population expansion

Factors affecting total fertility rate

• Total fertility rate (TFR) = the average number of

children born per female

• Replacement fertility = TFR that keeps the size of a

population stable

• Increasing urbanization decreases TFR
  • children go to school
  • increase costs
• With social security…elderly parents need fewer

children to support them

• Greater education allows women to enter the labor

force…with less emphasis on child rearing

Life expectancy is increasing

• Natural rate of population change = due to birth

and death rates alone

• countries with good sanitation, health care, and food…people live longer
• Life expectancy = average number of years that

an individual is likely to continue to live

• increased due to reduced rates of infant mortality
• urbanization, industrialization, and personal wealth

The demographic transition’s four stages

Population growth is seen as a temporary phenomenon docsity.com

Is the demographic transition

universal?

• It has occurred in Europe, U.S., Canada, Japan,

and other nations over the past 200-300 years

• It may or may not apply to all developing

nations:

• Transition theory could fail in cultures that…
  • Place greater value on childbirth or
  • Grant women fewer freedoms

For people to attain the material standard of living of

North Americans, we would need the natural resources of four and a half more Earths

Population policies and family planning work

• Many countries provide incentives, education,

contraception, and reproductive health care

• Funding and policies that encourage family

planning lower population growth rates in all

nations

• Thailand has an educational based approach to family planning and its growth rate fell from 2.3% to 0.6%
• Brazil, Mexico, Iran, Cuba, and other developing countries have active programs

Poverty and population growth are correlated

• Poorer societies have higher growth rates than wealthier

societies

• consistent with the demographic transition theory
• they have
  • higher fertility and growth rates
  • lower contraceptive use 99% of the next billion people added will be born in poor, less developed regions that are least able to support them docsity.com

The wealth gap and population growth cause conflict

• The richest 20% use 86% of the world’s resources
  • leaves 14% of the resources for 80% of the world’s people to share
• Tensions between “haves” and “have-not’s” are

increasing

HIV/AIDS impacts African populations

• The AIDS epidemic is

having the greatest

impact since the Black

Death in the 14th

century

• Of 33 million infected,

two-thirds live in sub-

Saharan Africa; 3,

die/day

• Low rates of

contraceptive use

spread the disease