HUMAN POPULATION DYNAMICS

Is the World Overpopulated?

Much of the world’s population growth occurs in developing countries like China and India.The world’s population is projected to increase from 7 billion to 10.8 billion by 2050.

Fig. 6-1, p. 125

Five Most Populous Countries, 2010 and 2050

Fig. 6-4, p. 127

Is the World Overpopulated?Some argue that the planet has too many people.Some feel that the world can support billions of more people due to technological advances.Constant debate over the need to reduce population growth.

Must consider moral, religious, and personal freedom.Do not know how long we can continue increasing the earth’s carrying capacity for humans. Likely to be between 7.8-10.8 billion people on earth by 2050.97% of growth in developing countries living in acute poverty.

Limits on Population Growth

No population can increase its size indefinitely.As the human population grows, so does the global total human ecological footprintCultural carrying capacity

Total number of people who could live in reasonable freedom and comfort indefinitely, without decreasing the ability of the earth to sustain future generations

Population Growth Cycle

Biotic potential– a populations capacity for growthAs a population levels off, it fluctuates slightly above and below the carrying capacity.Biotic Potential ex. Housefly can

lay 120 eggs in each generation. If nothing hurt the eggs or the flies, in 7 generations there would be 6,182,442,727,320 flies.

Humans Are Not Exempt from Nature’s Population Controls

IrelandPotato crop in 1845

Bubonic plagueFourteenth century

AIDSGlobal epidemic

Exceeding Carrying Capacity: Move, Switch Habits, or Decline in Size

Over time species may increase their carrying capacity by developing adaptations.Some species maintain their carrying capacity by migrating to other areas.So far, technological, social, and other cultural changes have extended the earth’s carrying capacity for humans.

Features of PopulationsPopulations are dynamic and exhibit attributes that are not shown by the individuals themselves.These attributes can be measured or calculated and include:

Population size: the total number of organisms in the population.Population density: the number of organisms per unit area.Population distribution: the location of individuals within a specific area.

Features of PopulationsPopulation composition provides information relevant to the dynamics of the population, i.e. whether the population is increasing or declining.Information on population composition (or structure) includes:

Sex ratios: the number of organisms of each sex.Fecundity (fertility): the reproductive capacity of the females.Age structure: the number of organisms of different ages.

Population Dynamics

‣ The study of changes in the size and composition of populations, and the factors influencing these changes, is population dynamics.

‣ Key factors for study include:Population growth rate: the change in the total population size per unit time.Natality (birth rate): the number of individuals born per unit time.Mortality (death rate): the number of individuals dying per unit time.Migration: the number moving into or out of the population.

Population size is influenced by births…

…and deaths

Migration‣ Migration is the movement of

organisms into (immigration) and out of (emigration) a population. It affects population attributes such as age and sex structure, as well as the dynamics of a population.

Populations lose individuals through deaths and emigration.Populations gain individuals through births and immigration.Net Migration = Immigration – EmigrationNet Migration rate = Number of Immigrates/ Number of people in population.

Migrating species may group together to form large mobile populations

Wildebeest - land based migrationWildebeest - land based migration

Canada geese - aerial migrationCanada geese - aerial migration

‣ Population Density - number of individuals per unit area or volume.‣ Can affect how rapidly a

population can grow or decline. Ex. Biotic factors like disease.

‣ Some population control factors are not affected by population density. Ex. Abiotic factors like weather.

At low densities, individuals are spaced well apart. Exs: territorial, solitary mammalian species such as tigers.At high densities, individuals are crowded together. Examples: colonial animals, such as rabbits, corals, and termites.

Population Density

High density populations

Low density populations

(population

) = Population Densityarea

‣ A crude measure of population density tells us nothing about the spatial distribution of individuals in the habitat.

‣ The population distribution describes the location of individuals within an area.

Distribution patterns are determined by the habitat patchiness (distribution of resources) and features of the organisms themselves, such as territoriality in animals or autotoxicity in plants.Individuals in a population may be distributed randomly, uniformly, or in clumps.

Population Distribution

Clumped distribution in termites

More uniform distribution in cacti

‣ A population’s distribution is considered random if the position of each individual is independent of the others.

‣ Random distributions are not common; they can occur only where:

The environment is uniform and resources are equally available throughout the year.There are no interactions between individuals or interactions produce no patterns of avoidance or attraction.

‣ Random distributions are seen in some invertebrate populations, e.g. spiders and clams, and some trees.

Random Distribution

Spider populations appear to show a random distribution

‣ Uniform or regular distribution patterns occur where individuals are more evenly spaced than would occur by chance.

‣ Regular patterns of distribution result from intraspecific competition amongst members of a population:

Territoriality in a relatively homogeneous environment.Competition for root and crown space in forest trees or moisture in desert and savanna plants.Autotoxicity: chemical inhibition of plant seedlings of the same species.

Uniform Distribution

Saguaro cacti compete for moisture and show a uniform distribution

‣ Clumped distributions are the most common in nature; individuals are clustered together in groups.

‣ Population clusters may occur around a a resource such as food or shelter.

‣ Clumped distributions result from the responses of plants and animals to:

Habitat differencesDaily and seasonal changes in weather and environmentReproductive patternsSocial behavior

Clumped Distribution

Sociality leads to clumped distribution

Density Dependent Factors‣ Density dependent factors

exert a greater effect on population growth at higher population densities.At high densities, individuals:

Compete more for resources.Are more easily located by predators and parasites.Are more vulnerable to infection and disease.

‣ Density dependent factors are biotic factors such as food supply, disease, parasite infestation, competition, and predation.

Parasites can spread rapidly through dense populations

Competition increases in crowded populations

‣ The effect of density independent factors on a population’s growth is not dependent on that population’s density:

Physical (or abiotic) factors

temperatureprecipitationhumidityaciditysalinity etc.

Catastrophic eventsfloods and tsunamisfiredroughtearthquake and eruption

Density Independent Factors

‣ Population growth depends on the number of individuals added to the population from births and immigration, minus the number lost through deaths and emigration.This can be expressed as a formula:

‣ Crude birth and Crude death rates used which is #live births per 1000 per year and # of deaths per 1000 per year

Population Growth

Population growth =(Births – Deaths) + (Immigration – Emigration)

(B) (D) (I) (E)

Growth rate

Global population growth rate(Birth rate-death rate)/10

National population growth rate(Birth rate-death rate) + (immigration – emigration) / 10

If a population of 10,000 experiences 100 births, 40 deaths, 10 immigrants and 30 emigrants in a year, what is the national population growth rate?

Annual Rate of Natural Population Change (%)=

Birth rate – Death rate 1,000 people x 100

Rates of Population Change

Ecologists usually measure the rate of population change. These rates are influenced by environmental factors and by the characteristics of the organisms themselves.Rates are expressed as:

Numbers per unit time,e.g. 2000 live births per yearPer capita rate (number per head of population),e.g. 122 live births per 1000 individuals (12.2%)

Many invertebrate populations increase rapidly in the right conditions

Large mammalian carnivores have a lower innate capacity for increase

Populations becoming established in a new area for the first time are often termed colonizing populations.

They may undergo a rapid exponential (logarithmic) increase in numbers to produce a J-shaped growth curve when plotted over time.Exponential growth- growth that increases at a constant rate per unit of time. Ex. - the growth sequence 2, 4, 8, 16, 32, 64 and so on

In natural populations, population growth rarely continues to increase at an exponential rate.Factors in the environment, such as available food or space, act to slow population growth.

Exponential Growth

Colonizing Population

Here the number being added to the population per unit time is large.

Exponential (J) curve Exponential growth is sustained only when there are no constraints from the environment.

Here, the number being added to the population per unit time is small.

Lag phase

Popu

latio

n nu

mbe

rs (N

)

Time

Logistic Growth ModelAs a population grows and it encounters environmental resistance, its increase will slow, and it will stabilize at a level that can supported by the environment.This type of sigmoidal growth (S) produces the logistic growth curve when plotted over time.

Environmental resistance increases as the

population overshoots K.

Environmental resistance decreases as

the population falls below K.

Established PopulationCarrying capacity (K)

The maximum population density that can be supported by the

environment on a long term basis.

The population tends to fluctuate around an 'equilibrium level'. The fluctuations are caused by variations in the birth rate and death rate as a result of the population density exceeding of

falling below carrying capacity.

In the early phase, growth is exponential (or nearly so)

Lag phase

Logistic (S) curveAs the population grows, the rate of population increase slows, reaching an equilibrium level around the carrying capacity.Po

pula

tion

num

bers

(N)

The population encounters resistance to exponential growth as it begins to fill up the environment. This is called environmental resistance.

Time

Exponential and Logistic Population Growth: J-Curves and S-Curves

Fig. 5-15, p. 115

2.0 Population overshoots carrying capacity

Carrying capacity

1.5Population recovers and stabilizes

Num

ber o

f she

ep (m

illio

ns)

.5

Exponential growth

Population runs out of resources and crashes

1.0

1800 1825 1850 1875 1900 1925

Year

Populations grow rapidly with ample resources, but as resources become limited, its growth rate slows and levels off.

Numerical data collected during a population study can be presented as a table of figures called a life table.

‣ Life tables provide a summary of mortality for a population. The basic data are the number of individuals surviving to each age interval. This gives the ages at which most mortality occurs in a population.

Life Tables

Age (yr)

No. alive at the start of

the age interval

Proportion of original no.

surviving at the start of the age

interval

No. dying during the

age interval

Mortality (d)

0 142 1.000 80 0.563

1 62 0.437 28 0.452

2 34 0.239 14 0.412

3 20 0.141 5 0.250

4 15 0.106 4 0.267

5 11 0.078 5 0.454

6 6 0.042 4 0.667

7 2 0.014 0 0.000

8 2 0.014 2 1.000

9 0 0.0 – –

Life table for a population of the barnacle Balanus

‣ The age structure of a population can represented with a survivorship curve. Survivorship curves use a semi-log plot of the number of individuals surviving per 1000 in the population, against age.

Because they are standardized (as number of survivors per 1000), species with different life expectancies can be easily compared.The shape of the curve reflects where heaviest mortality occurs:

Survivorship Curves

Type I: late losslarge mammals

Type II: constant losssmall mammals, songbirds

Type III: early lossoysters, barnacles

Num

ber o

f su

rviv

ors

(log

scal

e)

Relative age

‣ Species with Type I or late loss survivorship curves show the heaviest mortality late in life. Mortality is very low in the juvenile years and throughout most of adult life.

Late loss curves are typical of species that produce few young and care for them until they reach reproductive age.Such species are sometimes called K- selected species and include elephants, humans, and other large mammals.

Type I Survivorship Curves

Mortality is very low in early life

Mortality increases rapidly in old age

‣ Species with Type II or constant loss survivorship curves show a relatively constant mortality at all life stages.

Constant loss curves are typical of species with intermediate reproductive strategies. Populations face loss from predation and starvation throughout life.Examples include some many types of songbirds, some annual plants, some lizards, and many small mammals.

Type II Survivorship Curves

Constant mortality.No one age class is any more susceptible than any other.

‣ Species with Type III or early loss survivorship curves show the highest mortality in early life stages, with low mortality for those few individuals reaching a certain age and size.

Early loss curves are typical of species that produce large number of offspring and lack parental care.Such species are r- selected species (opportunists), and include most annual plants, most bony fish (although not mouth brooders), and most marine invertebrates.

Type III Survivorship Curves

Population losses are high in early life stages

Mortality is low for the few individuals surviving to old age

Two parameters govern the logistic growth of populations.

The intrinsic rate of natural increase or biotic potential. This is the maximum reproductive potential of an organism, symbolized by the letter r.The saturation density or carrying capacity of the environment, represented by the letter, K.

We can characterize species by the relative importance of r and K in their life cycles.

‘r’ and ‘K’ Selection

r-selected speciesThese species rarely reach carrying capacity (K). Their populations are in nearly exponential growth phases for much of the year. Early growth, rapid development, and fast population growth are important.

K-selected speciesThese species exist near asymptotic density (K) for most of the time. Competition and effective use of resources are important.

Time

Popu

latio

n nu

mbe

rs (N

)

K-Selected SpeciesSpecies that are K-selected exist under strong competition and are pushed to use available resources more efficiently.

These species have fewer offspring and longer lives.They put their energy into nurturing their young to reproductive age.K-selected species include most large mammals, birds of prey, and large, long-lived plants.

Climate Fairly constant and/or predictable

Mortality Density-dependent

Survivorship Usually types I and II(late or constant loss)

Population sizeFairly constant in time.

Near equilibrium with the environment.

Competition Usually keen.Specialist niche.

Selection favors

Slower development, larger body size, greater

competitive ability, delayed reproduction,

repeated reproductions

Length of life Longer (> one year)

Leads to: Efficiency

Correlates of K-selected species

r-Selected SpeciesSpecies with a high intrinsic capacity for population increase are called r-selected or opportunistic species.

These species show certain life history features and, to survive, must continually invade new areas to compensate for being displaced by more competitive species.Opportunists include algae, bacteria, rodents, many insects, and most annual plants.

Climate Variable and/or unpredictable

Mortality Density-independent

Survivorship Often type III(early loss)

Populationsize

Fluctuates wildly. Often below K.

Competition Variable, often lax. Generalist niche.

Selectionfavors

Rapid development, high rm, early reproduction, small body size, single reproduction (annual)

Length of life Short, usually less than one year

Leads to: Productivity

Correlates of r-selected species

DemographyDemography is the study of human populations, their characteristics and changes. Demographics will measure:

Statistics about people, such as births, deaths, and where they live as well as total population size.

Science Focus: Projecting Population Change

Why range of 7.8-10.8 billion for 2050?

Demographers must:1. Measure statistics about people, such as birth,

deaths, and where they live as well as total population size.

2. Determine reliability of current estimates3. Make assumptions about fertility trends4. Deal with different databases and sets of

assumptions

The world population, now over 7.1 billion, is growing at the rate of about 80 million per year. Projections put the world population at between 8 and 12 billion in 2050, with nearly all of this growth expected in the developing world.

Developing countries include: Africa, Asia, Latin America, the Caribbean, and regions of Melanesia, Micronesia, and Polynesia.The human population has grown rapidly because of the expansion of agriculture and industrial production and lower death rates from improvements in hygiene and medicine.

Human Population Growth

Developing countries grew at 0.1% Developed countries grew at 1.5% (15 times faster)

Growth Rate and percent change

Growth rate includes the birth rate, death rate, immigration and emigration. Usually calculated using the formulas: Change in pop = (B+I) – (D+E)

% change = change in value/old value x 100%

If a population of 10,000 experiences 100 births, 40 deaths, 10 immigrants and 30 emigrants in a year, what is the annual percentage growth rate?

Doubling Time: Rule of 70Doubling time is the time it takes for the population to double the number of people in the current population. Calculated as 70 / % growth rate

70/ growth rate = doubling time

If a population of a country grows at a rate of 5% a year, the number of years required for the pop to double is what?

Growth Rate(% per year)

Doubling Timein years

700

0.5 140

1 70

2 35

3 23

4 18

14

6 12

7 10

10 7

Doubling Time: Rule of 70

Estimates of likely future growth of the world human population are highly uncertain and projections for 2050 range from a low of 7.7 billion to a high of 11.2 billion.

Global Population Growth

Note: The latest ‘medium variant’ U.N. projection of 9.37 billion is nearly 500 million (4.7%) lower than the 9.83 billion projected in 1994.

Global Human Population GrowthHigh fertility rate: 11.2 billion

Medium fertility rate: 9.4 billion

Low fertility rate: 7.7 billion

North America

Latin America & Caribbean

Europe

Asia & Oceania

Africa

Demographic TransitionsProcess where countries become economically developed then their birth and death rates begin to decline. In the past this was referred to as “first” and “third” world countries or “developed” and “developing”.Currently this process is described by the different stages according to population growth:

Preindustrial stage shows little population growth due to high birth rate with high death rate.Transitional stage is where industrialization begins, death rates drops and birth rates remain high. Rapid population growth occurs.Industrial stage is birth rate dropping and approaching death rate. Population growth slowly declines.Postindustrial stage are birth rate and death rate become similar and population growth slows or declines.

Demographic Transition

Generalized model of demographic transition shows that the total fertility of a society decreases as the society progresses through the demographic transition.

Some developing countries may have difficulty making the demographic transition.

Demographic Transition

‣ Age structure refers to the number of organisms of different ages. Populations can be broadly grouped into those individuals of:

pre-reproductive agereproductive agepost reproductive age

Analysis of the age structure of populations can assist in their management because it can indicate where most population mortality occurs and whether or not reproductive individuals are being replaced.

Age Structure

Size/age classes in fish

Human Age StructureHuman age structure varies from country to country.Number of people younger than age 15 is the major factor determining a country’s population growth.In developing countries age structure tends to be in favor of younger individuals with a large proportion being under 15 years.

In developed nations, age structure is relatively even throughout the age groups.

Age Structure in Human Populations

Changes in distribution of a country’s age groups have long-lasting economic and social impacts.

Determining Population Growth The rate at which a population grows or declines depends on its age structure. Age structure diagrams show the distribution of different age groups. These groups are further broken into cohorts:

Prereproductive age (0-14) are persons who are not mature enough to reproduceReproductive age (15-44)are those persons that are capable of reproduction.Postreproductive age (45+) are those persons too old to reproduce.

Age Structure Diagrams: Histograms

Age StructureSince age structure diagrams are broken down by age, demographers can obtain:

Birth rateMaturity rateDeath rate of an entire population.

These diagrams are usually broken down by country and divided into genders.

29% of the people in developing countries were under 15 years old in 2012 versus only 16% in developed countries.

Age Structure: United States

Because of baby boom, the US has a bulge(yellow) in the pyramid with people in their 50’s-60’s.There are more women than men in the older group because of differences in longevity between sexes.

Rapid Growth Diagram

‣Pyramid shaped histograms have a birth rate that exceeds the death rate. Lower cohorts have more males and females.

‣Population growth is rapid in countries that have a pyramid shape.Current modern examples include Africa, Asia, and Latin America

Slow/Stable Growth Diagrams

‣When the histogram shape is “box”-like, then stable or slow growth is represented.

‣Birth rate is almost equal to death rate. Sometimes called Zero growth.Current examples of slow growth: USA, Australia, & Canada

Current examples of stable growth: Denmark, Austria, & Italy

Negative Growth Diagrams

‣If there is declining or negative growth, then the birth rate with be less than the death rate.

‣Pyramids with declining populations tend to show larger numbers of older persons in their population.

Current examples: Germany & Japan

Slow decline manageableRapid decline causes severe economic and social problems.

How do we pay for services for elderly?

Fig. 6-15, p. 138

Some Problems with Rapid Population Decline

Can threaten economic growth

Labor shortages

Less government revenues with fewer workers

Less entrepreneurship and new business formation

Less likelihood for new technology development

Increasing public deficits to fund higher pension and health-care costs

Pensions may be cut and retirement age increased

Developing vs. DevelopedDeveloping (Transitional, Third World):

Higher infant mortality rate because of a shortage in prenatal and pediatric care. Thus, they have more children to ensure some survive.Agricultural societies need children to help in the labor force.Lower per capita income or poorer countries need children to provide an income and sometimes contraceptives are not affordable.Women lack education and job opportunities.

Developed (Industrial, First World):Usually don’t have population problems but can be linked to poverty.Educated and working women tend to delay childbearing.Pension systems support people as they age.Family planning and the ability to control fertility.Higher cost of raising children causes people to have smaller families.Abortion is legal.

Where Population Growth Occurred, 1950-2010

Fig. 6-3, p. 123

UrbanizationUrbanization is the movement of people from rural areas into cities Urban areas must import most of its food, water, energy, minerals, & other resources because of large populationsLarge populations produce and consume enormous quantities of resources that can pollute the air, water & land.Disease can easily spread in urban areas because of the high density population.44% of world’s people live in urban areas that occupy only 5% of world’s land and they consume 75% of the world’s resources.

UrbanizationEnvironmental pressures of urbanization from population growth are reduced because birth rates in urban areas usually are 3-4x’s lower than in rural areas because cities provide education opportunities. Some countries, including China, penalize couples who have more than one or two children by:

1. Raising their taxes2. Charging other fees3. Eliminating income tax deductions for a couple’s third

child4. Loss of health-care benefits, free education, food

allotments and job options

Mortality and FertilityInfant mortality rate: The number of child and/or infant deaths.

If a mother lives in an area with a high infant mortality rate she will tend to have a lot of children to ensure some will make it to adulthood. This ensures care for aging parents and a labor force.Infant mortality rate is higher in developing countries than in developed countries.Along with life expectancy, the infant mortality rate is a good indicator of the quality of life of a country

Replacement-level fertility: the number of children a couple must bear to replace themselves.

Slightly higher than two children per couple. (2.1 in developed countries and 2.5 in some developing countries.)

Total Fertility RatesFertility rate – number of children born to a woman during her lifetime.Total fertility rate (TFR): the average number of children a woman has during reproductive years.

In 2012, the average global Total Fertility Rate was 2.4 children per woman.1.6 in developed countries (down from 2.5 in 1950.)3.0 in developing countries (down from 6.5 in 1950).

If fertility rate drops to replacement level fertility but the population continues to grow, this is called population momentum and can be seen in pyramid shaped age structure diagrams.Birth rates and fertility rates have been slowed or decreased because:

Cultural/religious practices prohibited birth control.Cultural/religious practices favored large families.Education/Employment/Status of women is low

Based on current trends, it is assumed that human fertility rates will continue to decline and life expectancy will continue to increase. Developing countries are expected to broadly follow these demographic trends.

Fertility Rates

Trends in Fertility Rates

South & Central America

Africa

Asia

Developing

Developed

Where are we going?

Fig. 6-B, p. 130

11 UN high-fertility variant (2008 revision)U.S. Census Bureau (2008 update)

10UN low-fertility variant (2008 revision)IIASA (2007 update)

9

8

Wor

ld p

opul

atio

n (in

bill

ions

)

7

62010 2020 2030 2040 2050

Year

UN medium-fertility variant (2008 revision)

Factors Affecting Birth Rates and Fertility Rates

The number of children women have is affected by:The cost of raising and educating them.Availability of pensions.Urbanization.Education and employment opportunities.Infant deaths.Child careMarriage age.Religious beliefs, politics, and cultural normsAvailability of contraception and abortion.

Factors Affecting Death RatesDeath rates have declined because of:

Increased food supplies, better nutrition due to Green Revolution

Advances in medicine. (Antibiotics and vaccines)Improvement in prenatal or neonatal careImproved sanitation, safer water supplies and personal hygiene due to Industrial Revolution.

U.S. infant mortality is higher than it could be (ranked 49th world-wide by CIA and 30th by Save the Childeren) due to:

Inadequate pre- and post-natal care for poor.Drug addiction.High teenage birth rate.

More children live past childbirth

Fertilizers and pesticides increased

crop yields

Fig. 6-10, p. 129

Infant Mortality Rates, 1950-2010

Populations Can Decline from a Rising Death Rate: The AIDS Tragedy

30 million killed: 1981-2012Many young adults die: loss of most productive workersSharp drop in life expectancyInternational community

Reduce the spread of HIV through education and health careFinancial assistance and volunteers

Fig. 6-15, p. 134

Human population growth is slower than predicted but because of the large and increasing population size the world population is still expected to increase substantially before stabilizing.

Population Stabilization

Progress Towards Population Stabilization

South & Central America

Africa

Asia Developing

Developed

Demographics in the USA

The baby bust that followed the baby boom was largely due to delayed marriage, contraception, and abortion.

Now becoming senior citizens (Graying of America) In 2012, the total fertility rate in the United States was slightly > 2.0

Demographics in the USANearly 2.3 million people were added to the U.S. in 2012:

70% occurred because of births outnumbering deaths30% came from illegal and legal immigration. Population increase in recent years has been because of immigrationTFR in U.S. dropped

Rate of population growth has slowed.

Current US Population: 320,367,731

Fig. 6-11, p. 135

Legal Immigration to the U.S. between 1820 and 2006

Fig. 6-7, p. 132

20th Century Lifestyle Changes in the U.S.

Developed CountriesHigh rates of resource use because of the availability of resources, production, and waste.Result in high levels of pollution and environmental degradation per person because of control methods, clean up, and education.The measure of a country’s economic growth is the Gross National Product (GNP) or the Gross Domestic Product (GDP).The Human Development Index is also commonly used to determine development.

Most developed countries have a GDP that is high and a population growth rate that is low.

Developing CountriesChina, the largest, has taken drastic population control methods.By 2050, India is predicted to pass China. Pakistan is projected to become 3rd (the US is 3rd now.)Russia is losing 600,000 people a year, after being the 4th largest country in 1950 due to pollution, crime, corruption, hyperinflation, disease, and despair.Environmentalists are concerned about resource use because developing countries are increasing their standard of living.

Environmental Impact Equation (Paul Ehrlich Formula)Population X affluence X technology = Environmental impactEstimated that a US citizen consumes 35x’s as much as the average citizen of India and 100x’s as much as the average person in the world’s poorest countries.

Thus, poor parents in a developing country would need 70-200 kids to have the same lifetime environmental impact as 2 typical US kids.

‣ India has tried population control methods with modest success. Poor planning, bureaucratic inefficiency, low status of women and lack of support have led to low success. The family planning method calls for:

Education of women including basic literacy.Encouraged education of contraception use among women & birth spacing.

‣ Possible problems include:Cultural/Social issues.Cost of programs.

India’s Population Control

‣ China has used a government-enforced program, “One-Child Policy”, to reduce the fertility rate. The One-Child Policy includes:

Paid leave to women for fertility operations.Monthly Subsidy to one-child families.Tuition and job priorities for only children.Housing preferences.Additional food rations.Monetary compensation.

‣ Problems include: Preference toward genderIncrease in orphansConsequences or punishment for multiple births

China’s Population Control

Core Case Study: Slowing Population Growth in China: A Success Story

1.35 billion peopleCurrently, China’s TFR is 1.5 children per women.China has moved 300 million people out of poverty.China’s policy penalizes couples who have more than one or two children by:

Raising their taxes, charging other fees, eliminating income tax deductions for a couple’s third child, and loss of health-care benefits, food allotments and job options

Total fertility rate

Percentage of worldpopulation

Population

Population (2050)(estimated)

Illiteracy (% of adults)

Population under age 15 (%)

Population growth rate (%)

17%20%

1.1 billion1.3 billion

1.6 billion

IndiaChina

GDP PPP per capita

Percentage livingbelow $2 per day

Life expectancy

47%17%

36%20%

1.6%0.6%

1.4 billion

$5,890$3,120

47 80

70 years62 years

2758

1.6 children per women (down from 5.7 in 1972)Infant mortality rate

2.9 children per women (down from 5.3 in 1970)

1994 Global (Cairo) Conference: Population & Development

The summit at Cairo, Egypt, encouraged action to stabilized the world’s population at 7.8 billion by 2050, instead of the projected 11-12.5 billion.

Provide universal access to family-planning servicesImprove the health care of infants, children & pregnant women and improve the status of women by expanding education & job opportunitiesEncourage development of national population policiesIncrease men’s involvement in child-rearing responsibility & family planning and increase access to education for girlsTake steps to eradicate poverty

INFLUENCING POPULATION SIZEThe best way to slow population growth is:

Investing in family planning(has reduced number of births and abortions throughout world).Reducing poverty.EducationElevating the status of women by not suppressing their human rights and having paying job outside of home.

Family planning in less-developed countriesResponsible for a 55% drop in TFRsFinancial benefits: money spent on family planning saves far more in health, education costs

Global Contraceptive Usage

Two problems1.42% pregnancies

unplanned, 26% end with abortion

2.Many couples do not have access to family planning

Thomas Malthus 1798 “diminishing returns” – Human population increases exponentially while food supplies increase at a slower linear rateArgued rising wages and improved well-being would lead to excess reproduction among the working class.

A labor surplus would then cause wages to fall below subsistence levels, resulting in starvation, disease and crime.

Argued, land for food production was limiting factor in both population growth and economic development.

Problems with a Growing Population

Problems with a Growing PopulationReasons for World Hunger Issues

Unequal distribution of available foodLoss of arable landIncreasing population growth rateIncreasing poverty in developing countries

Strategies for ensuring adequate nutrition for a growing population:

Increase the number of new food crops from a diversity of plant speciesDistribute food more equitablyIncrease land are that is dedicated to grain production rather than meat productionAssist developing countries in efficient crop irrigation systems.

Environmental ImpactDeforestation destroys habitats and reduces biodiversity:

Farming and the creation of monocultures, housing or development projects that cause urbanization, fuel from wood, and fossil fuel recovery from mining.

Fossil fuel burning releases CO2:Results in climate change, change in temperature and precipitation patterns changing habitats.

Intensive fishing and fish farming:Spreads disease to native fish and causes unsustainable fish populations.

Diversion and damming of water:For agricultural, municipal, and industrial use reduces water supplies.

Building landfills:To accommodate increased amounts of trash.

HUMAN ASPECTS ON NATURAL SYSTEMS

We have used technology to alter much of the rest of nature in ways that threaten the survival of many other species and could reduce the quality of life for our own species.