Cunningham - Cunningham - Saigo: Environmental Science 7 th Ed. Human Populations.

Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

Human Populations


Outline:

• Population Growth Limits to Growth

• Human Demography Fertility and Mortality Life Span and Expectancy

• Population Growth - Opposing Factors• Demographic Transition• Family Planning• Future of Human Populations


POPULATION GROWTH

• Until the Middle Ages, human populations were held in check by diseases, famines and wars, and thus grew very slowly. It took all of human history to reach 1 billion. 150 years to reach 3 billion 12 years to go from 5 to 6 billion (1999)

- Population 3x during 20th c.


Human Population History


LIMITS TO GROWTH

• Thomas Malthus (1798) argued human populations tend to increase exponentially while food production is plentiful. Humans inevitably outstrip food supply and

eventually collapse.- Human population only stabilized by

positive checks.- Humans are too lazy and immoral to

voluntarily reduce birth rates.


Malthus Theory of “Overpopulation”


Social Justice Perspective

• Population growth is a symptom rather than a root cause of poverty and other social problems. Real causes of these problems are

exploitation and oppression.- The way to slow population growth and

alleviate many social problems is through social justice.


Population Perspectives Today

• Neo-Malthusians - Believe we are approaching, or have already surpassed, the Earth’s carrying capacity. We should make over-population issues

our first priority.• Social Justice - Believe eliminating

oppression and poverty through social justice is the only solution to the population problem. Wealth and resource distribution must be

addressed.


The Role of Technology

• Technological optimists argue that Malthus was wrong in his predictions because he failed to account for scientific progress.

Current burst of growth was stimulated by the scientific and industrial revolutions.


Can More People be Beneficial ?

• More people mean larger markets, more workers, and increased efficiency due to mass productions.

• Greater numbers also provide more intelligence and enterprise to overcome problems. Human ingenuity and intelligence.


DEMOGRAPHY

• Vital statistics about people

Births, deaths,

distribution, and

population size.


Population Density (persons / square km)


Two Demographic Worlds

• Periphery is poor, young, and rapidly growing.

- Contain 80% of world population, and will account for 90% of projected growth.

• Core is wealthy, old, and mostly shrinking.- Average age is about 40.- Populations expected to decline.


Estimated Human Population Growth


Fertility Rate(# children per woman of childbearing age)


Population growthin Periphery:

Cause or symptomof poverty and environmental degradation?


Ehrlich Theory of “Population Bomb”

• Population growth would deplete resources Can be true on local/national level

• Treats population as cause


Core responsibility for Periphery growth

• Core consumes far more resources

• Demands cheap, unskilled young labor

• Population growth as a symptom of poverty


Why parents in Periphery have kids

Better chance for one kid to survive

Bring in the crops and income

Help parents in old age

Women often lack power to not have kids


Fertility declines, real and projected

1

2

3

4

5

6

7

1950 1965 1980 1995 2010 2025 2040

Children per Woman

(2.1 = no population growth)

Developing

Developed

Africa

Asia

South andCentralAmerica


Women’s empowerment:Contraception Rates


Policies to lower birth rate

• Voluntary Availability of birth control Incentives for small families

• Forced One-child policy (China) Coercive “population control”

•Social–Empowerment of women–Better health care and education–End to child labor–Social security


Fertility and Birth Rates

• Crude Birth Rate - Number of births in a year per thousand. (Not adjusted for population characteristics)

• Total Fertility Rate - Number of children born to an average woman in a population during her life.

• Zero Population Growth - Occurs when births plus immigration in a population just equal deaths plus emigration.


Mortality and Death Rates

• Crude Death Rate - Number of deaths per thousand persons in a given year. Poor countries average about 20 while

wealthier countries average about 10.- Some rapidly growing countries have

very low crude death rates compared to slower growing countries, due to a higher proportion of young people in the population.


Population Growth Rates

• Natural Increase (Crude Birth Rate - Crude Death Rate)

• Total Growth Rate Includes immigration and emigration


Life Span and Life Expectancy

• Life Expectancy - Average age a newborn can expect to attain in any given society. Declining mortality is the primary cause of

most population growth in last 300 years.

Worldwide, average has risen from 40 to 65.5 over the past century.

- Greatest progress has been in developing countries.


Demographic Implications of Living Longer

• A population growing rapidly due to natural increase has more young people than a stationary population. Both rapidly and slowly growing countries

can have a problem with dependency ratio.- The number of non-working compared to

working individuals in a population.


Germany (effect of wars)


Canada, 1971-2006


Russia, 1990-2006


Emigration and Immigration

• Emigration and Immigration play a large role in human population dynamics.

Developed regions expect 2 million immigrants a year for next 50 years.

Locals complain immigrants take away jobs and overload social services.

Sierra Club debate over immigation.


POPULATION GROWTH, OPPOSING FACTORS

• Pronatalist Pressures Factors that increase the desire for children.

- Source of pleasure, pride, comfort.- Source of support for elderly parents.- Current source of family income.- Social Status- Replace members in society as they die.

Boys frequently valued more than girls.


Birth Reduction Pressures

• Higher education and personal freedom for women often result in decisions to limit childbearing. When women have more opportunities to

earn a salary, they are less likely to have children.

Education and socioeconomic status are usually inversely related to fertility in wealthier countries.


Birth Reduction Pressures

• In developing countries, higher income often means families can afford more children, thus fertility often increases.

• In less-developed countries, adding another child to a family usually does not cost much, while in developed countries, raising an additional child can carry significant costs.


United States Birth Rate


DEMOGRAPHIC TRANSITION

• Model of falling death rates and birth rates due to improved living conditions accompanying economic development. Pre-Modern Society - Poor conditions keep

death rates high, thus birth rates are correspondingly high.

Economic Development brings better conditions and standard of living thus death rates fall. Birth rates stay constant or even rise.


Demographic Transition

• Eventually, birth rates begin to fall. Populations grow rapidly in time between

death rates and birth rates fall.• Developed Countries - Transition is complete

and both death and birth rates are low and population is in equilibrium.


Demographic Transition


Optimism or Pessimism

• Some demographers believe the Demographic Transition is already taking place in developing countries, and world population should stabilize during the next century.

• Others argue that many poorer countries are trapped in the middle phase of transition, and that their populations are growing so rapidly that human demands exceed sustainable resource yields.


Social Justice

• Still other demographers believe that in order for the Demographic Transition model to work, resources must be distributed more equitably. The world has enough natural resources,

but inequitable social and economic systems cause maldistribution.


FAMILY PLANNING

• Family Planning allows couples to determine the number and spacing of their children.

• Birth Control - Any method used to reduce births. Traditional Methods

- Long breast-feeding, taboos against intercourse while breast-feeding, celibacy, folk medicines, abortion, infanticide.


FUTURE OF HUMAN POPULATIONS

• Most demographers believe the world population will stabilize sometime during the next century. Projections of maximum population size:

- Low 8 billion- Medium 9.3 billion- High 13 billion

Cunningham - Cunningham - Saigo: Environmental Science 7 th Ed. Human Populations.

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