lecture outlines chapter 8 environment: the science behind the stories 4th edition

© 2011 Pearson Education, Inc.

Lecture Outlines

Chapter 8

Environment:The Science behind the Stories

4th Edition

Withgott/Brennan


This lecture will help you understand:• Human population growth• Different viewpoints on this

growth• Population, affluence, and

technology’s effects• Demography • Demographic transition• Factors affecting population

growth• The HIV/AIDS epidemic• Population and sustainable development


Case study: China’s one-child policy• In 1970, China’s 790 million

people faced starvation• The government instituted a

one-child policy- The growth rate plummeted- The policy is now less strict

• The successful program has unintended consequences:- Killing of female infants - Black-market trade in

teenage girls


Our world at seven billion• Populations continue to rise in most countries

- Particularly in poverty-stricken developing nations

• Although the rate of growth is slowing, we are still increasing in numbers

It would take 30 years, counting once each second, to count to a billion! It would take 210 years to count to 7 billion!


The human population is growing rapidly• Our population grows by over 80 million each year• It took until 1800 to reach 1 billion• In 1930 (130 years later) we reached 2 billion• We added the most recent billion in 12 years

Due to exponential growth, even if the growth rate remains steady, population will continue to grow


Rates of growth vary from region to region

• At today’s 1.2% global growth rate, the population will double in 58 years (70/1.2 = 58)

• If China’s rate had continued at 2.8%, it would have had 2 billion people in 2004


Is population growth a problem?• Technology, sanitation, medication, and increased food

increase population- Death rates drop, but not birth rates

• Population growth was seen as good- Support for elderly, a larger labor

pool• Thomas Malthus’ An Essay on the

Principles of Population (1798)- Humans will outstrip food supplies- War, disease, starvation reduce

populations


Paul Ehrlich’s Population Bomb (1968)

• Neo-Malthusians: population growth will increase faster than food production

• Population growth causes famine and conflict- Civilization would end by the

end of the 20th century• Intensified food production fed

more people


Population growth will affect quality of life

• Population growth has caused famine, disease, conflict• Prosperity, education, gender equality reduce birth rates• Cornucopians (e.g., economists) say new resources will

replace depleted ones- But some resources (e.g., species) are irreplaceable

• Quality of life will suffer with unchecked growth- Less space, food, wealth per person


Some governments fear falling populations

• Policymakers believe population growth increases economic, political, and military strength

• But growth is correlated with poverty, not wealth- Strong, rich nations have low growth rates- Weak, poor nations have high growth rates

• Some nations offer incentives for more children- Elderly need social services

• 49% of non-European nations feel their birth rates are too high


Population growth affects the environment

• The IPAT model: I = P × A × T × S• Total impact (I) on the environment results from:

- Population (P) = individuals need space and resources- Affluence (A) = greater per capita resource use- Technology (T) = increased exploitation of resources- Sensitivity (S) = how sensitive an area is to human

pressure• Further model refinements include the effects of

education, laws, and ethics on the formula


Population growth with limited resources• Impact equates to pollution or resource consumption

- Humans use 25% of Earth’s net primary production• Technology has increased efficiency and reduced our

strain on resources- Resulting in further population growth- For example: increased agricultural production

• Modern China’s increasing affluence is causing:- Increased resource consumption- Farmland erosion, depleted aquifers, urban pollution

• China shows us what the rest of the world can become


Population growth: causes and consequences


Human population growth and regulation


Demography

• Demography: the application of population ecology to the study of change in human populations- All population principles apply to humans- Environmental factors limit population growth

• Humans raise the environment’s carrying capacity through technology

• How many humans can the world sustain? - 1–33 billion: prosperity to abject poverty- Population growth can’t continue forever


Demography

• Demographers study: - Population size - Density and

distribution- Age structure- Sex ratio - Birth, death, immigration, and

emigration rates


Population size and density

• The UN predicts 9 billion by 2050

• Increased density impacts the environment- But relieves pressure in

less-populated areas• Highest density: temperate,

subtropical, tropical biomes- Cities

• Lowest density: away from water


Population distribution• Humans are unevenly distributed around the globe• Unpopulated areas tend to be environmentally sensitive

(high S value in the IPAT equation)- Vulnerable to humans (e.g., deserts, arid grasslands)


Age structure affects population size• Age structure diagrams (population pyramids) show age

structure• Wide base = many young:

- High reproduction - Rapid population growth

• Even age distribution:- Remains stable- Births = deaths


Canada’s age structure is balanced

Madagascar’s age structure is heavily weighted toward the young

Age structures: Canada vs. Madagascar


Changing age structures pose challenges

• China’s age structure is changing- In 1970, the median age was 20- By 2050, it will be 45

• By 2050, over 300 million will be over 65 - Fewer people will be

working to support social programs


Many populations are aging• Many populations are getting older

- They will need care and financial assistance- Taxes will increase for Social Security and Medicare

• But fewer dependentchildren means lower crime rates

• The elderly can remain productive


Sex ratios

• Human sex ratios at birth slightly favor males - For every 100 females born, 106 males are born

• Chinese females are selectively aborted- 120 boys were reported for 100 girls- Cultural gender preferences - The government’s one-child policy

• The undesirable social consequences?- Many single Chinese men- Teenage girls are kidnapped and sold as brides


Factors in population change

• 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 caused decreased deaths- The increased gap between birth and death rates

resulted in population expansion• Natural rate of population change = due to birth

and death rates alone


Immigration and emigration

• War, civil strife, and environmental degradation cause people to flee their homes- Each year, 25 million refugees escape poor

environmental conditions• This movement causes environmental problems

- No incentives to conserve resources


Falling growth rates do not mean fewer people

Slower rates of growth do not mean a decreasing population—population size continues to increase


Factors affecting total fertility rate

• Total fertility rate (TFR) = the average number of children born to each female

• Replacement fertility = the TFR that keeps the size of a population stable (about 2.1)

• Causes of decreasing TFR:- Medical care reduces infant mortality- Urbanization increases childcare costs- Children go to school instead of working - Social Security supports the elderly- Educated women enter the labor force


Life expectancy is increasing

• In 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- Increases with reduced rates of infant mortality

• Urbanization, industrialization, and personal wealth reduce infant mortality rates

• Demographic transition = a model of economic and cultural change - Explains the declining death and birth rates in

industrializing nations


The demographic transition

• A stable pre-industrial state of high birth and death rates changes to a stable post-industrial state of low birth and death rates

• As mortality decreases, there is less need for large families- Parents invest in quality of life

• Death rates fall before birth rates- Resulting in population growth


The demographic transition’s four stages

Population growth is seen as a temporary phenomenon


Is the demographic transition universal?

• It has occurred in Europe, the U.S., Canada, Japan, and other nations over the past 200–300 years

• But it may or may not apply to developing nations• The transition 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


Birth control: key to controlling growth

• The greatest single factor slowing population growth• Birth control = controlling the number of children born

- Reducing the frequency of pregnancy• Contraception = deliberate prevention of pregnancy

through a variety of methods• Family planning = affects the number and spacing of

children- Clinics offer advice, information, and contraceptives- Hindered by religious and cultural influences- Rates range from 10% (Africa) to 90% (China)


Contraceptive methods for birth control


Empowering women reduces growth rates

• Fertility rates drop when women gain access to contraceptives, family planning programs, and educational opportunities

• Women with little power have unintended pregnancies- Two-thirds of the world’s illiterate are women

Educating women reduces fertility rates, delays childbirth, and gives them a voice in reproductive decisions


We are a long way from gender equity

• Over 60% of the world’s poor are women• Violence against women remains shockingly common

- Many men resist women’s decision making• The gap is obvious at high levels of government

- We are a long way from achieving gender equality

The U.S. lags behind the world in proportion of women representatives


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’s educational-based approach to family

planning reduced its growth rate from 2.3% to 0.6%- Brazil, Mexico, Iran, Cuba, and other developing

countries have active programs• 1994’s UN population conference in Cairo, Egypt called

for universal access to reproductive health care


Family planning reduces fertility rates

Blue = with family planning

Red = without family planning


Poverty and population growth are correlated• Poorer societies have

higher population growth rates- Consistent with the

demographic transition theory

- They have higher fertility and growth rates, with 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


Correlation of poverty and population

• Poverty exacerbates population growth - Population growth exacerbates poverty

• In 1960, 70% of all people lived in developing nations- As of 2010, 82% live in these nations- 99% of the next billion will be born in these nations


Poverty causes environmental degradation• Population growth in poor nations increases

environmental degradation- Farming degrades soil in arid areas (Africa, China)- Poor people cut forests, deplete biodiversity, and hunt

endangered species (e.g., great apes)

Africa’s Sahel and western China are turning to desert


Wealth also impacts the environment• The population problem is not only in poor countries • Affluent societies have enormous resource consumption

and waste production- People use resources from other areas, as well as

from their own- Ecological footprints are huge

• We are living beyond our means

One American has as much environmental impact as 4.5 Chinese or 10 Indians or 19 Afghans


The Earth can’t support our consumption

Humanity’s global ecological footprint surpassed Earth’s capacity in 1987

• Biocapacity = the amount of biologically productive land and sea available to us- Ecological deficit = ecological footprint > biocapacity- Ecological reserve = ecological footprint < biocapacity

• We are running a global ecological deficit


The wealth gap and population growth cause conflict• The contrast between rich and poor societies causes

social and environmental stress- The richest 20% use 86% of the world’s resources- Increasing tensions between “haves” and “have-nots”


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; 3,800 die/day• Low rates of contraceptive use spread the disease

HIV is established and spreading quickly around the world


AIDS has severe effects

• AIDS undermines the ability of poor nations to develop- Millions of orphans are created- Fewer teachers and workers to fill jobs- Families and communities break down- Income and food production decline- Debt and medical costs skyrocket


Demographic fatigue• Demographic fatigue = governments face

overwhelming challenges related to population growth- With the added of stress of HIV/AIDS, governments

are stretched beyond their capabilities- Problems grow worse and citizens lose faith

• Good news: HIV transmission has slowed recently

Decreased AIDS deaths are due to policy, collaboration, research, NGOs, and grassroots efforts


Sustainable development and population

• Millennium Development Goals = UN’s 2000 declaration - Specific targets can be met with concrete strategies- Global partnerships with corporations, governments,

etc.• Population control is not a goal

- But to achieve the goals, population growth and resource consumption must be addressed


Millennium Development Goals


Conclusion

• The human population is larger than at any other time• Rates are decreasing but populations are still rising• Most developed nations have passed through the

demographic transition• Expanding women’s rights slows population growth• How will the population stop rising?

- The demographic transition, governmental intervention, or disease and social conflict?

• Sustainability requires a stabilized population to avoid destroying natural systems

lecture outlines chapter 8 environment: the science behind the stories 4th edition

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