ap environmental science human population: growth, demography and carrying capacity “can we...
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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
© Brooks/Cole Publishing Company / ITP
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
© Brooks/Cole Publishing Company / ITP
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
© Brooks/Cole Publishing Company / ITP
-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
© Brooks/Cole Publishing Company / ITP
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
1.1 billion1.4 billion
294 million
349 million
219 million308 million
179 million
211 million
159 million
229 million
144 million137 million
141 million
205 million
128 million
121 million
137 million206 million
Population Size and FertilityPopulation Size and Fertility
© Brooks/Cole Publishing Company / ITP
•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
© Brooks/Cole Publishing Company / ITP
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
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Typical effectiveness of birth control methods in the United States
The US is the #1 industrialized country for teen pregnancy rate
Birth ControlBirth Control
© Brooks/Cole Publishing Company / ITP
Typical effectiveness of birth control methods in the United States (continued):
Death RatesDeath Rates
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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
© Brooks/Cole Publishing Company / ITP
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.
Birth and Death Rates Over TimeBirth and Death Rates Over Time
© Brooks/Cole Publishing Company / ITP
In developed countries decreases in death rates are being accompanied by decreases in birth rates over time.
Fig.11–11a
Birth and Death Rates Over TimeBirth and Death Rates Over Time
© Brooks/Cole Publishing Company / ITP
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
© Brooks/Cole Publishing Company / ITP
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.
Population Age StructurePopulation Age Structure
© Brooks/Cole Publishing Company / ITP
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.
Population Age StructurePopulation Age Structure
© Brooks/Cole Publishing Company / ITP
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
Population Age StructurePopulation Age Structure
© Brooks/Cole Publishing Company / ITP
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
294 million179 million
137 million
349 million211 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 StructurePopulation Age Structure
© Brooks/Cole Publishing Company / ITP
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
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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
© Brooks/Cole Publishing Company / ITP
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
© Brooks/Cole Publishing Company / ITP
Fig.11–20
Demographic transition- a generalized model that explains how death rates fall before birth rates when a country becomes industrialized.
Demographic TransitionDemographic Transition
© Brooks/Cole Publishing Company / ITP
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.
Demographic TransitionDemographic Transition
© Brooks/Cole Publishing Company / ITP
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.
Demographic TransitionDemographic Transition
© Brooks/Cole Publishing Company / ITP
Fig.11–20
3) Industrial Stage: Birth rate drops and eventually approaches a balance with death rate, leading to a slowing of population growth.
Demographic TransitionDemographic Transition
© Brooks/Cole Publishing Company / ITP
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.
Demographic TransitionDemographic Transition
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%
1.1 billion1.3 billion
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
© Brooks/Cole Publishing Company / ITP
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
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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
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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
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Tobacco use is the leading cause of preventable death (data from 1993).
Physical HazardsPhysical Hazards
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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
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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
Biological HazardsBiological Hazards
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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
Biological HazardsBiological Hazards
© Brooks/Cole Publishing Company / ITP
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
Biological HazardsBiological Hazards
© Brooks/Cole Publishing Company / ITP
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