Environmental ScienceEnvironmental ScienceCh.9 Guided Notes: Human PopulationCh.9 Guided Notes: Human Population

IntroductionIntroductionPaul Ehrlich published Paul Ehrlich published The Population The Population Bomb in 1968.Bomb in 1968.

IntroductionIntroduction

It created a lot of controversy. One of the It created a lot of controversy. One of the premises of the book is that any premises of the book is that any environmental issue is really just a human environmental issue is really just a human overpopulation issue.overpopulation issue.

Ehrlich believed that:Ehrlich believed that: Every environmental problem is directly Every environmental problem is directly

related to there being too many people on related to there being too many people on earth.earth.

The way to help the environment is to The way to help the environment is to control over populationcontrol over population

Questions to Ponder:Questions to Ponder:

Do we have a human population problem?Do we have a human population problem? If so, is overpopulation at the root of all If so, is overpopulation at the root of all

environmental problems?environmental problems?

Can the population be controlled?Can the population be controlled?

What strategies exist to keep population in What strategies exist to keep population in check, and will these measures help the check, and will these measures help the environment?environment?

Section 1: Studying Human Section 1: Studying Human PopulationsPopulations

Demography Demography is the study of populations is the study of populations but most often refers to the study of but most often refers to the study of humanhuman populations populations..

Demographers studyDemographers study the historical size and make up of populations the historical size and make up of populations

of countries in order to make comparisons and of countries in order to make comparisons and predictions.predictions.

Properties that affect population growth such as Properties that affect population growth such as economics and social structureeconomics and social structure

Demographers group countries into Demographers group countries into 2 categories:2 categories:

Developed countriesDeveloped countries have higher have higher average incomes, slower population average incomes, slower population growth and diverse industrial economiesgrowth and diverse industrial economies

Developing countriesDeveloping countries have lower have lower average incomes, simple and agriculture-average incomes, simple and agriculture-based economies, and rapid population based economies, and rapid population growthgrowth

How Does a Species Population How Does a Species Population Change?Change?

BirthBirth ( add more individuals) ( add more individuals)

DeathDeath (remove individuals) (remove individuals)

Migration Migration (immigration/emigration)(immigration/emigration)

Assuming no migrationAssuming no migration

If Births > Deaths, the population If Births > Deaths, the population growsgrows

If Births < Deaths, the population If Births < Deaths, the population declinesdeclines

Over the course of many years, Over the course of many years, population changes oscillate around population changes oscillate around a a dynamic equilibriumdynamic equilibrium..

The Human Population Over TimeThe Human Population Over Time

After growing slowly for thousands of After growing slowly for thousands of years, the human population grew years, the human population grew rapidly in the 1800s. The increase rapidly in the 1800s. The increase was was exponential exponential (J-curve) (J-curve) See Fig. 1 pg.235See Fig. 1 pg.235

This is the This is the Standard Growth Curve.Standard Growth Curve.

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Most hunter/gatherer populations existed Most hunter/gatherer populations existed before 10 KYA.before 10 KYA.

These populations were very small and These populations were very small and had very little population growth.had very little population growth.

Death rates and birth rates were both very Death rates and birth rates were both very highhigh

Catastrophic population crashes were also Catastrophic population crashes were also possiblepossible

The The Agricultural RevolutionAgricultural Revolution resulted resulted in a greater rate of population gowthin a greater rate of population gowth

better living conditionsbetter living conditions

Increase in birth rate due to the Increase in birth rate due to the abundance of foodabundance of food

Occurred through the development of Occurred through the development of cultivation of animals and plants.cultivation of animals and plants.

Occurred in many regions of the world.Occurred in many regions of the world.

The The Industrial Revolution Industrial Revolution resulted resulted inin

• Greater rise in populationGreater rise in population

• Decreased death rateDecreased death rate

• Increased birth rateIncreased birth rate

• Better health care and medicineBetter health care and medicine

• Better nutrition and sanitation practicesBetter nutrition and sanitation practices

• Increase in food productionIncrease in food production

• Technological advances in just about every field increasedTechnological advances in just about every field increased

• Demand for labor may have contributed to the increase in the Demand for labor may have contributed to the increase in the population.population.

The world population reached 1 billion The world population reached 1 billion for the first time in 1830for the first time in 1830

The world population reached 2 billion The world population reached 2 billion in 1930., only 100 years since 1830!in 1930., only 100 years since 1830!

Exponential Growth CurveExponential Growth Curve

The population doubles with each The population doubles with each generation.generation.

Growth is very slow at first, but as Growth is very slow at first, but as population increases over time, the population increases over time, the growth rate becomes enormous.growth rate becomes enormous.

Carrying capacityCarrying capacity – the maximum – the maximum number of individuals that the number of individuals that the environment can support.environment can support.

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Forecasting Population Size Forecasting Population Size ( Factors that affect population growth)( Factors that affect population growth)

Age structure – the distribution of Age structure – the distribution of ages in a specific population at a ages in a specific population at a certain timecertain time

If a population has more young If a population has more young people than old, the population size people than old, the population size will likely increase as the young will likely increase as the young grown and reproducegrown and reproduce

If a population has more older people If a population has more older people than young, the population will likely than young, the population will likely decreasedecrease

Population pyramidPopulation pyramid – a double-sided – a double-sided bar graph that shows age distribution bar graph that shows age distribution of a population.of a population.

Age PyramidAge Pyramid

http://www.infovis.net/printMag.php?lang=2&num=158http://www.infovis.net/printMag.php?lang=2&num=158

SurvivorshipSurvivorship

The percentage of members of a The percentage of members of a group that are likely to survive at group that are likely to survive at any given age.any given age.

To predict survivorship, To predict survivorship, demographers studies a group of demographers studies a group of people born at the same time and people born at the same time and notes when each person dies.notes when each person dies.

Type I survivorshipType I survivorship – wealthy – wealthy countries such as Japan and countries such as Japan and Germany. Most people live to be Germany. Most people live to be very oldvery old

Type II survivorshipType II survivorship – populations – populations have a similar death rate at all ages.have a similar death rate at all ages.

Type III survivorshipType III survivorship is the pattern in is the pattern in very poor human populations in very poor human populations in which many children die.which many children die.

Fertility RateFertility Rate

The number of babies born each year per The number of babies born each year per 1,000 women in a population.1,000 women in a population.

Total fertility rateTotal fertility rate – the average number of – the average number of children a woman gives birth to in her children a woman gives birth to in her lifetimelifetime

Replacement levelReplacement level – the average number – the average number of children each parent must have in order of children each parent must have in order to replace themselves in the population.to replace themselves in the population.

MigrationMigration

The movement of individuals between The movement of individuals between areasareas

Immigration Immigration – movement into an area– movement into an area

EmigrationEmigration – movement out of an area. – movement out of an area. The populations of many developed The populations of many developed

countries might be decreasing if not for countries might be decreasing if not for immigration.immigration.

Declining Death RatesDeclining Death Rates

More people now have access to More people now have access to clean water, adequate food and safe clean water, adequate food and safe sewage disposal.sewage disposal.

Discovery of vaccines in the 20Discovery of vaccines in the 20thth century contributed to declining century contributed to declining death rates (polio, small pox, death rates (polio, small pox, diptheria)diptheria)

Life ExpectancyLife Expectancy The average number of years members of The average number of years members of

a population are likely to live.a population are likely to live. Most affected by Most affected by infant mortality – the infant mortality – the

death rate of infants less than a year old.death rate of infants less than a year old.

By 2000, the rate of infant mortality was By 2000, the rate of infant mortality was less than one-third the rate in 1900.less than one-third the rate in 1900.

Infant health is most affected by the Infant health is most affected by the parents’ access to education, food, fuel, parents’ access to education, food, fuel, and clean water.and clean water.

Demographic TransitionDemographic Transition

A model that describes how economic and A model that describes how economic and social changes affect population growth social changes affect population growth rates.rates.

Stage 1Stage 1 – society is in pre-industrial – society is in pre-industrial condition.condition.

Birth rate and death rates are at high levelBirth rate and death rates are at high level Population stable.Population stable. The world was in this stage until 1700’sThe world was in this stage until 1700’s

Stage 2Stage 2 – population explosion occurs. – population explosion occurs. Death rates decline as hygien, nutrition and Death rates decline as hygien, nutrition and

education improve.education improve. Population can double in less than 30 years.Population can double in less than 30 years.

Stage 3Stage 3 – population growth slows because the birth – population growth slows because the birth rate decreases.rate decreases.

population stabilizespopulation stabilizes

Stage 4Stage 4 – birth rate drops below replacement level, – birth rate drops below replacement level, so the size of the population begins to decrease.so the size of the population begins to decrease.

Takes from one to three generations for the Takes from one to three generations for the demographic transition to occur in most demographic transition to occur in most developed countries.developed countries.

Women and FertilityWomen and Fertility

The factors most clearly related to a The factors most clearly related to a decline in birth rates are increasing decline in birth rates are increasing education and economic education and economic independence for women.independence for women.

Large families are valuable in Large families are valuable in communities in which children work communities in which children work or take care of older family or take care of older family members.members.

Section 2 : Changing Population Section 2 : Changing Population TrendsTrends

Populations that have high rates of Populations that have high rates of growth create environmental growth create environmental problemsproblems

Resources are used at an increased Resources are used at an increased rate and can overwhelm the rate and can overwhelm the infrastructure of a communityinfrastructure of a community

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Symptoms of an Overwhelming Symptoms of an Overwhelming PopulationPopulation

Suburban sprawlSuburban sprawl Overcrowded schoolsOvercrowded schools Polluted riversPolluted rivers Barren landBarren land Inadequate housingInadequate housing

Problems of OvercrowdingProblems of Overcrowding

Shortage of fuelwood – Shortage of fuelwood – wood is the main wood is the main fuel source for boiling water and cooking foodfuel source for boiling water and cooking food

Unsafe water Unsafe water – the main water supply used – the main water supply used for washing, drinking AND sewage. Water for washing, drinking AND sewage. Water systems cannot be expanded fast enough to keep systems cannot be expanded fast enough to keep up with growthup with growth

Shortage of arable land Shortage of arable land

Managing Population GrowthManaging Population Growth

China, Thailand, India China, Thailand, India use public use public advertising, family planning programs, economic advertising, family planning programs, economic incentives, legal punishment, forced abortion.incentives, legal punishment, forced abortion.

1994 – The United Nations held the 1994 – The United Nations held the International Conference on International Conference on Population and Development(ICPD)Population and Development(ICPD) and set goals to stabilize population growth and set goals to stabilize population growth through investments in development, and through investments in development, and improving women’s status.improving women’s status.

Growth is SlowingGrowth is Slowing

7 billion!!! Current population7 billion!!! Current population

Fertility rates decliningFertility rates declining

Most countries will have replacement Most countries will have replacement level fertility rates by 2050, if so, level fertility rates by 2050, if so, world population growth would world population growth would eventually stopeventually stop

United States FactsUnited States Facts

PopulationPopulation: : 313,232,044 (July 2011)313,232,044 (July 2011) Age StructureAge Structure:: 0-14 years: 20.1% 0-14 years: 20.1% 15-64 years: 66.8% 15-64 years: 66.8% 65 years and over: 13.1%65 years and over: 13.1%

Birth Rate: Birth Rate: 13.83 births/1,000 population 13.83 births/1,000 population

Per couplePer couple: 2.1 in 2005 (Europe 1.3): 2.1 in 2005 (Europe 1.3)

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