ap environmental science human population: growth, demography and carrying capacity “can we...

AP Environmental ScienceAP Environmental Science

Human Population:Human Population:Growth, Demography and Growth, Demography and

Carrying CapacityCarrying Capacity“Can we stabilize population by reducing

fertility before nature takes over and stabilizes our numbers by raising mortality?” Lester

Brown

© Brooks/Cole Publishing Company / ITP

1. Factors Affecting Human 1. Factors Affecting Human Population SizePopulation Size


Human population is currently growing exponentially.

-Earth History

-What will be the ultimate size of the human population?

-What is Earth's carrying capacity?

World Population ClockWorld Population Clock

Factors Affecting Human Population Factors Affecting Human Population SizeSize


Population ChangeBirths

+Immigration

Deaths+

Emigration–=

Population change is calculated as the difference between individuals entering and leaving a population:

-Birth rate- the number of births per year

-Death rate- the number of deaths per year

-Zero population growth (ZPG)- occurs when factors that increase and decrease population size balance.

-NOTE: when considering world population growth rates, immigration and emigration play no part (YET!)

DemographyDemographyDemography- the study of changes in size, composition and distribution of human populations.

Demographers study these trends, as well as their causes and consequences.

Birth RatesBirth RatesBirth rates are the numbers of births/year.

Seems equal, right? But what if Country A has 1000 people and Country B has 10,000? Which country is potentially growing faster?

45 BIRTHS/YEAR

Country A

45 BIRTHS/YEAR

Country B

BIRTH RATE BIRTH RATE

Crude Birth and Death RatesCrude Birth and Death Rates

Crude birth rate- number of births per year/1000 people. Crude death rates calculated in the same way. – LDC’s typically have higher crude birth and

death rates—Africa #1– Birth rates in LDC’s: 1.5%– Birth rates in MDC’s: 0.1%

Crude RatesCrude RatesCrude birth rates take into account the population size and shows a better picture of what is actually happening.

45 BIRTHS/YEAR/1000Country A

4.5 BIRTHS/YEAR/1000

Country B

CRUDE BIRTH RATE:

CRUDE BIRTH RATE:

Average crude birth rate Average crude death rate

World

All developedcountries

All developingcountries

Developingcountries

(w/o China)

21

9

11

10

24

8

27

9

© 2004 Brooks/Cole – Thomson Learning

Africa

LatinAmerica

Asia

Oceania

UnitedStates

NorthAmerica

Europe

38

14

22

6

20

7

18

7

14

8

14

8

10

12

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Population Growth RatesPopulation Growth Rates


-The annual rate of population growth is generally expressed as a percentage that is representative of the growth per year. Note the distribution of growth rates in 1998.

-To figure the % rate: (Popfinal - Popinitial) / Popinitial X 100

OR use the rule of 70!

Population ChangePopulation ChangeBetween 1963 and 2004 the world’s annual

population growth dropped 41% from 2.2% to 1.25%.– In this same time, the world population doubled

to 6.4 billion.– A small, exponential population growth rate can

still have large effects, especially if the population base is large.

– The world is currently adding another New York City every month.

The Most Populous CountriesThe Most Populous Countries


The world’s top five most populated countries :#1 China1.3 billion#2 India1.1 billion

-These two countries together make up 37% of the world’s total population#3 United States#4 Indonesia#5 Brazil

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India

USA

Indonesia

Brazil

Pakistan

Russia

Bangladesh

Japan

Nigeria

2004 2025

1.3 billion1.4 billion


294 million

349 million

219 million308 million

179 million

211 million

159 million

229 million


141 million

205 million

128 million

121 million


Population Size and FertilityPopulation Size and Fertility


•Fertility- the number of births that occur to an individual woman or in a population.•Two types of fertility rates that affect a country’s population size and growth rate:

•1)Replacement-level fertility rate•2)Total fertility rate (TFR)

Replacement-Level Fertility vs. Replacement-Level Fertility vs. Total Fertility RateTotal Fertility Rate

Replacement-level fertility: the number of kids a couple must have to replace themselves.

2.1 developed, 2.5 developing due to fact that some females die before reproducing

Reaching replacement levels does not mean immediate halt in population growth b/c many future parents are still alive.

Replacement-Level Fertility vs. Replacement-Level Fertility vs. TFRTFR

Total fertility rate: the average number of kids a woman typically has during her reproductive years.These have dropped sharply since 1950’s– Developed: 2.51.5– Developing 6.53.1 ** Highest currently in Africa

World

Developedcountries

Developingcountries

Africa

LatinAmerica

Asia

Oceania

NorthAmerica

Europe

5 children per woman2.8

2.5

1.6

6.53.1

6.65.1

5.92.6

5.92.6

3.82.1

3.52.0

2.61.4

1950 2004

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Total Fertility RateTotal Fertility RateThe expected population in future years depends on the world’s projected average TFR (high:2.5, medium:2.0, low:1.5)

97% of the growth in all three estimates is projected to take place in developing countries.

2008 TFR for world 2.5

Interactive TFR graph

High

Medium

Low

12

11

10

9

8

7

6

5

4

3

21950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050

High10.6 billion people

Medium8.9 billion people

Low7.2 billion people

Year

Po

pu

lati

on

(b

illio

ns)

Total Fertility in the United StatesTotal Fertility in the United States


Fig.11–9

-In the U.S. the time of the highest TFR was in the 1950’s after WWII. This was called the “Baby Boom.”-Total fertility in the United States had a major increase during the "baby boom" (1946–64) and is now hovering just below replacement level.

Factors Affecting Fertility RatesFactors Affecting Fertility RatesEducation and affluenceImportance of child laborUrbanization—access to family planning– Availability of reliable birth control– Availability of legal abortions

Cost of raising and educating childrenEducational and employment opportunities for women– Decreased infant mortality– Average age of marriage

Availability of pensionsReligious beliefs, traditions, and cultural norms

Birth ControlBirth Control


Typical effectiveness of birth control methods in the United States

The US is the #1 industrialized country for teen pregnancy rate

Birth ControlBirth Control


Typical effectiveness of birth control methods in the United States (continued):

Death RatesDeath Rates


Infant death rates are lower in developed countries than developing countries.

Fig.11–12

Death RatesDeath RatesInfant mortality- the number of babies of every 1,000 born who die before their first birthday.

At least 8 million infants (most in developing) die of preventable causes during their first year of life22,000 per day = 55 jumbo jet crashes with no survivors.

**Life expectancy and infant mortality rates (deaths/1000 before first birthday) determine health of people in a country.

Birth and Death Rates Over TimeBirth and Death Rates Over Time


The rapid growth in the world's population has not resulted from an ↑ in birth rates, but a ↓ in death rates.

• Death rates have ↓ markedly during past 100 years

• Birth rates have also ↓, but not as fast as death rates

• The increasing difference between birth and death rates is what has lead to exponential population growth

• Patterns of change in birth and death rates are different for developed vs. developing countries.



In developed countries decreases in death rates are being accompanied by decreases in birth rates over time.

Fig.11–11a



In developing countries decreases in death rates have not been accompanied by as large of decreases in birth rates over time, leading to major population increase.

Fig.11–11b

2. Population Age Structure2. Population Age Structure

Age structure- refers to the proportion of the population in each age class:– Prereproductive (0–14 years)– Reproductive (15–44 years)– Postreproductive (45 and up)

Population Age StructurePopulation Age Structure


Age structure of a rapidly growing vs. a slower growing population.

Fig.11–13a

Rapidly growing populations have pyramid–shaped age structures, with large numbers of prereproductive individuals. Slower growing populations have a more even age distribution.



Age structure of populations with zero growth vs. negative growth.

Fig.11–13b

-Populations with zero population growth have nearly equal proportions of prereproductive and reproductive individuals;

-Populations with negative growth have a greater proportion of reproductive than prereproductive individuals.



Developing countries are expected to continue to have a pyramid shape through the year 2025, although the age structure will become somewhat more evenly distributed.

Fig.11–14a



Populations of developed countries are expected to have an increasingly even age distribution through the year 2025.

Age Structure Video Clip from hippocampus.org

Fig.11–14b

Population(2004)

Populationprojected

(2025)

Infantmortality

rate

Lifeexpectancy

Fertilityrate (TFR)

%Populationunder

age 15

% Populationover

age 65

Per capitaGDP


137 million


206 million

6.733

100

77 years

71 years52 years

2.02.2

5.7

21%30%

44%

12%6%

3%

$36,110$7,450

$800

United States (highly developed)

Brazil (moderately developed)

Nigeria (less developed)

© 2004 Brooks/Cole – Thomson Learning



Population age structure of the United States continues to show a bulge as the baby boom generation ages. This has been compared to watching a boa constrictor swallow a pig.

Fig.11–15

3. Solutions: Stabilizing Human 3. Solutions: Stabilizing Human PopulationPopulation


In 1972 the projections of a model, published in The Limits to Growth, indicated that if current economic, resource use and population trends continue then we can expect economic and ecological collapse in the next century.

-The results of this admittedly crude model challenged basic assumptions of industrial societies that there are no limits to industrial and population growth

-20 later the authors updated their work in Beyond the Limits: Confronting Global Collapse, Envisioning a Sustainable Future (Donella Meadows et al. 1992)

-Despite limitations, computer models are an effective means for exploring possible future scenarios.

Computer Models of Human Computer Models of Human PopulationPopulation


Fig.11–18

This computer model projects what might happen if the world's population and economy continue to grow exponentially at 1990 levels.

Computer Models of Human Computer Models of Human PopulationPopulation

© Brooks/Cole Publishing Company / ITPFig.11–19

This computer model projects how we can avoid overshoot and collapse to make a fairly smooth transition to a sustainable future by stabilizing fertility at two children per couple.

Demographic TransitionDemographic Transition


Fig.11–20

Demographic transition- a generalized model that explains how death rates fall before birth rates when a country becomes industrialized.



Fig.11–20

1) Preindustrial Stage: both birth and death rates are relatively high (harsh living conditions) and approximately equal, such that the population does not increase, and the population size is small.



Fig.11–20

2) Transitional Stage: The population grows rapidly b/c death rate decreases markedly due to industrialization, increased food production, and improved health care.

Birth rates remain relatively high, so the population grows rapidly.



Fig.11–20

3) Industrial Stage: Birth rate drops and eventually approaches a balance with death rate, leading to a slowing of population growth.



Fig.11–20

4) Postindustrial Stage: Birth rate and death rates approximately balance, zero population growth (ZPG) is attained, and the population stabilizes at a size much higher than the preindustrial size.

If birth rate declines below death rate negative population growth may even be attained.


Most developing countries are in the transitional stage because death rates have fallen.Some analysts believe that some of the conditions needed the developing countries to develop are no longer available.– Skilled workers to compete in today’s economy– Capital and resources for economic development– Some have a sharp rise in debt to other countries,

leaving little for improvement– Receive less economic assistance since 1980’s

Demographic transition at hippocampus.org

Pre-industrial Transitional Industrial Post-industrial

4. Case Studies4. Case Studies

Immigration in the U.S.– As TFR decreases,

immigration has become a major source of population increase

– In 1998 we received about 935,000 legal immigrants and 400,000 illegal--40% of our annual population growth!

– Working immigrants boost the economy in the long run

– Increasing levels of legal and illegal are expected.

– The TFR of immigrants in the U.S. is greatly higher than those of the rest of the population

Case Studies: IndiaCase Studies: India

Population control in India– In 1952 India began the first

national family planning program

– The program has been disappointing because of poor planning, inefficiency, low status of women, extreme poverty, and lack of funds

– Couples still have an average of 3.5 children because of the belief that they need children to work and care for them in old age.

– TFR 2.74 in 2008

Case Studies: ChinaCase Studies: ChinaPopulation control in China:– Since 1970, with the world's

largest population, has initiated efforts to better feed its people and control population growth

– Family planning successful– Strict population control

measures prevent couples from having more than one child

– Although considered coercive, the policy is significantly slowing population growth.

– TFR 1.77 in 2008

Percentageof world

population

Population

Population (2025)(estimated)

Illiteracy (%of adults)

Population under age 15(%)

Population growth rate (%)

Total fertility rate

Infant mortality rate

Life expectancy

GDP PPP per capita

17%20%


1.4 billion

1.4 billion

47%17%

36%

22%

1.7%0.6%

3.1 children per woman (down from 5.3 in 1970)1.7 children per woman (down from 5.7 in 1972)

6432

62 years

71 years

$2,650

$4,520

IndiaChina

Family Planning WorldwideFamily Planning WorldwideFamily planning: – Provide info about prenatal care – Help parents space births– Help parents regulate family size

Globally family planning:– Raised the use of modern

contraception by married women in LDC’s from 10% in 1960’s to 50% in 2004

– Responsible for at least 55% of the drop in TFR’s in LDC’s from 6 in 1960 to 3.1 in 2004

5. Human Population and 5. Human Population and SustainabilitySustainability


How can governments reduce population growth?-Improve access to family planning

-Improve heath care for infants, children, and pregnant women

-Encourage development of national population policies

-Improve equality between men and women

-Increase access to education, especially for girls

-Increase the involvement of men in child rearing and family planning

-Reduce poverty

-Reduce and eliminate unsustainable patterns of production and consumption.

Women Empowerment and Women Empowerment and SustainabilitySustainability

Three factors that lead to women having fewer, healthier children– Education– Job outside home – Equal rights

Women do 60-80% of the work associated with growing food, gathering fuel and hauling water in rural areas

Women Empowerment and Women Empowerment and SustainabilitySustainability

Globally women account for 2/3 of all hours worked but….– Receive only 10% of the world’s income – Own 2% of the world’s land– Receive a low status of care….

Approximately 39,000 BABY girls in China die EVERY YEAR (3250/month) due to lack of treatment that their male counterparts normally receive.Girls in India from 1 to 5 years old die more often than 50% of their male counterparts.

Equality would slow population growth, promote freedom, reduce poverty and slow environmental degradation.Women in India

6. Risks and Hazards6. Risks and Hazards


Risk- the possibility of suffering harm from a hazard that can cause injury, disease, economic loss or environmental damage.

-Risk expressed as a probability (1 in 250)

-Risk assessment- using data, hypotheses and models to estimate the probability of harm to human health, society, or the environment that may result from exposure to specific hazards

-Risk management- deciding how or whether to reduce a possible risk to a certain level and at what cost.

Major HazardsMajor Hazards


There are four major types of hazards:

-Chemical hazards from harmful chemicals in air, water, soil and food…already discussed in Ch 3

-Cultural hazards, such as unsafe working conditions, smoking, poor diet, drugs, drinking, driving, criminal assault, unsafe sex and poverty.

-Physical hazards, such as noise, fire, tornadoes, hurricanes, earthquakes, volcanic eruptions, floods and ionizing radiation.

-Biological hazards from pathogens, pollen and other allergens and animals, such as bees and poisonous snakes.

Cultural HazardsCultural Hazards


Tobacco use is the leading cause of preventable death (data from 1993).

Physical HazardsPhysical Hazards


Preventing loss:

-Understand where risk is high

-Establish building codes to regulate placement and design of buildings in high risk areas

-Determine if prediction is feasible.

Map of expected damage

from earthquakes.

Physical HazardsPhysical HazardsIonizing radiation has enough energy to damage body tissues.

Biological HazardsBiological Hazards


Biological hazards include both non-transmissible and transmissible diseases.

-Non-transmissible diseases- those not passed from one person to another (diabetes, emphysema and malnutrition)

-Transmissible diseases- caused by bacteria, viruses, protozoa, or parasites, and can be passed from one person to another (colds, flus, hepatitis, STD’s, malaria)

-Globalization is increasing the spread of some transmissible diseases (Lyme disease carried by ticks and spread by people is now widespread over North America)

7 Deadliest Infectious Diseases7 Deadliest Infectious Diseases



The complex life cycle of Plasmodium, a 500,000 year old protist that causes malaria, involves transmission between infected individuals by Anopheles mosquitoes .

Malaria Video



Worldwide distribution of malaria today (red) and its projected distribution in 2046 (orange). If the world becomes warmer, as projected by current climate models, by 2046 malaria could affect 60% of the world’s population.

Case Study: Growing Germ Case Study: Growing Germ Resistance to AntibioticsResistance to Antibiotics

1 bacteria can produce 16,777,216 offspring in 24 hours– This allows them to become

genetically resistant to antibiotics through natural selection

Other factors that play a role in the increase in serious infectious bacterial diseases– Globalization– Overuse of pesticides– Overuse of antibiotics

Case Study: Growing Germ Case Study: Growing Germ Resistance to AntibioticsResistance to Antibiotics

Overuse of antibiotics– 50% prescribed unnecessarily– Available in some countries

without a prescription– In U.S., 75% are fed to

livestock.Resistant strains can spread to humans through contact with infected animals

– Every major disease-causing bacterium now has strains that resist at least one of the roughly 160 existing antibiotics.

– Antibiotic Resistance Video

Case Study: The Global Case Study: The Global Tuberculosis ThreatTuberculosis Threat

TB bacterium kills about 1.7 million people a year and could kill 28 million by 2020It is an airborne pathogen– It has infected 1 in 3 people in

the world– May be in the body, whether

you are sick or not– Over ½ the infected people

do not know they are infected and do not feel sick

– Silent global epidemic

Case Study: The Global Case Study: The Global Tuberculosis ThreatTuberculosis Threat

Increase in TB caused by– Lack of screening and control programs– Antibiotic resistance – Population growth and urbanization – AIDS weakens immune system and allows TB to

multiplyCan be cured by a combination of 4 inexpensive drugs– Must be taken daily for 6-8 months– Symptoms disappear, people think they are cured and

stop taking their medicine causing disease to recur in more resistant form

TB Evolution Movie

VirusesVirusesHIV (human immunodeficiency virus) transmitted by– Unsafe sex, sharing of needles, infected

mother to offspring before or after birth, and exposure to infected blood.

Influenza (flu) is transmitted by body fluids and airborne emissions of infected persons– 1918 Swine Flu killed 500 million

worldwide (20-30 million in U.S.)– Today flu kills 1 million per year worldwide

(20,000 in the U.S.)

VirusesVirusesHepatitis B virus (HBV) damages the liver and is transmitted same way as HIV--vaccineWest Nile virus transmitted by mosquitoes that have been feeding on infected birds2002 Severe Acute Respiratory Syndrome virus (SARS) emerged in China and is easily transmitted.Human Papillomavirus (HPV) causes venereal warts and several types of cancer—50% of all sexually active people will get it in their lifetimes—vaccineUganda: Out of the Wild

HBV Risk Areas

VirusesVirusesViral infections are harder to fight than infections caused by bacteria and protozoa.– Drugs that kill viruses harm the

cells of the host– Antibiotics are useless and increase

genetic resistance in body’s bacteria

– Main issue is prevention!!!!– Vaccines stimulate the immune

system to produce antibodies to ward off viral infections and help reduce the spread of viral diseases

Polio, influenza, measles, smallpox, rabies, and hep B.Many viral diseases do not have vaccines like HIV



Generalized model of the epidemiological transition that may take place as countries become more industrialized.

Biological HazardsBiological HazardsWhat are some ways we reduce infectious diseases?

-Reduce overcrowding, unsafe drinking water, poor sanitation, inadequate health care systems, malnutrition and poverty

-Increase funding for disease monitoring

-Reduce antibiotic use to prevent evolution of resistant organisms

-Protect biodiversity as a means of reducing disease spread

-Increase research.

-Careful hand washing

ap environmental science human population: growth, demography and carrying capacity “can we...

Documents

population change

birth rates birth rates

world population growth

population base

crude rates crude birth

population growth zpg

population size balance

crude death rates