Chapter 9: Applying Population Ecology: The Human Population and Its Impact

December 2011

Human Population Growth: Historical PerspectiveThe human population has experienced exponential

growth over the past 200 years. Why?

Expanded into diverse habitats and climate zones.Development of modern agricultureModern sanitation and public health advancesDevelopment of antibiotics and vaccinationsHarnessed concentrated sources of energy

The Bottom LineNo population can continue to grow indefinitely.Degradation of natural systems and resources jeopardizes our ability to

sustain populations and build economies.Differential effect of developed vs. developing countries

In 2006, developed countries added 1.2 million people Developing countries added 79.5 million people.

Population Growth Projections

By 2050, human population is projected to be between 7.2 and 10.6 billion people.

97% of the growth in developing countries.

Factors Affecting Human Population Size

When births plus immigration exceed deaths plus emigration, population increases; when the reverse is true, population declines.

This is true of other species as well as humans.

Comparison of birth rates and death rates

Demographers use:

Birth rate or crude birth rate: number of live births per 1,000 people in a population in a given year (U.S. – 14.18)

Death rate or crude death rate: number of deaths per 1,000 people in a population in a given year (U.S. – 8.27)

Declining Population: Observing Fertility Rates

Fertility – number of children born to a woman during her lifetime.replacement –level fertility - number of children a couple

must bear to replace themselves Typically between 2.1 and 2.5 children per couple

Total fertility (TFR) – average number of children a woman typically has during her reproductive years Global average about 2.7 Developed countries about 1.6

United States – 2.06 Developing countries about 2.9 Range according to CIA (0.91 in Macau and 7.68 in Niger)

Population Projections

Case Study: Fertility and Birth Rates in the U.S.

1900 – 76 million AmericansBaby boom – post WWII – 1946 to 1964

Birth rate up to 3.7 at one pointCorresponding “baby bust” – 1964 to 1977

Due to delayed marriage, contraceptive use, and abortion2007 – saw 300 millionth American

56% growth due to birth rate, 44% due to immigrationImmigration shift from Europe to Latin American/Southeast

AsiaHigh per capita resource use

Case Study: Fertility and Birth Rates in the U.S.

Case Study: Fertility and Birth Rates in the U.S.

Think about how life has changed…

Case Study: Fertility and Birth Rates in the U.S.

In the United States in 1905… Three leading causes of death: pneumonia,

tuberculosis, and diarrhea 90% of doctors had no college education 1 out 5 adults cannot read or write Average U.S. worker earns $200-$400 per

year Only 9,000 cars in the U.S. with 144 miles of

paved roads 3 minute phone call cost $11 30 people live in Las Vegas, NV Most women washed their hair once a

month

In the United States NOW… Three leading causes of death: heart

disease, cancer, stroke Common path to becoming a physician

requires 8 years of college and 3-8 years of internship and residency

99% literate Average U.S. worker earns $42,028 per

year (2005 figures according to Worldsalaries.com)

450 million cars in the U.S. with 5.7 million miles of paved roads

3 minute phone call costs $0.51 (according to Mr. Bromwell’s cell phone plan)

567,641people live in Las Vegas, NV I would imagine hair washing is daily

among other things…

Tractor-plow, 1905

Factors Affecting Birth Rates and Fertility RatesImportance of children as part of the labor forceCost of raising and educating childrenAvailability of private and public pension systemsUrbanizationEducational and employment opportunities available for

womenInfant mortality rateAverage age at marriage (or first child)Availability of legal abortionsAvailability of reliable birth control methodsReligious beliefs, traditions and cultural norms

Factors Affecting Death RatesAvailability of food suppliesNutrition quality of available food suppliesAvailability of medical care, immunization, and

antibioticsSanitationSafe drinking water suppliesCivil, governmental, or societal unrest or disadvantageInfant mortality rate

Life Expectancy and Infant Mortality RateTwo useful indicators of overall health of a population:Life expectancy – average number of years a newborn

infant can expect to liveInfant mortality rate – number of babies out of every

1,000 born who die before their first birthdaySingle best measure of a society’s qualityReflects overall nutrition and health care

Infant Mortality in the U.S.

In U.S. approximately 6.3 deaths / 1,000 births

Higher than expected due to inadequate health care for poor women during pregnancy,

drug addiction among pregnant women,

and a high birth rate among teenagers.

Migration Immigration + emigrationSince 1820, U.S. admitted twice as

many immigrants as all other nations combined!

Legal vs. illegal immigrationRacial/ethnic shift Pros

‘land of opportunity’ Accept undesirable jobs, pay taxes,

create jobs Will replace aging boomer

generationCons

Increase countries population, strain resources

Magnet for world’s poor

Population Age StructureThe distribution of males and

females in each age group in the world’s population

Age structure diagrams Examine # of people in three age

categoriesprereproductivereproductivepostreproductive

Population Age Structure Diagrams

The Baby-BoomersThis generation makes up half of all adult workers and

dominates demand for goods and services.

Consequences of Population Decline• Can threaten economic growth • Less government revenues with fewer

workers• Reduces availability of young people for

military service• Less entrepreneurship and new

business formation• Less likelihood for new technology

development• Increasing public deficits to fund higher

pension and healthcare costs

Global Aging

The Demographic Transition

Fig. 9-15, p. 186

Total fertility rate

Percentageof world

populationPopulation

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

4780

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)

ReferencesAnnual Estimates of the Resident Population for Incorporated Places in Nevada: April 1, 2000 to July 1, 2009" (CSV). United States

Census Bureau, Population Division. 2010-09. http://www.census.gov/popest/cities/tables/SUB-EST2009-04-32.csv. Retrieved 2010-11-16

“Infant Mortality Rate (per 1,000 live births)” Digital Image. Unnatural Causes. 2008. California Newsreel. 11 January, 2009. http://www.unnaturalcauses.org/interactivities_04-6.php

Miller, G.T. Living in the Environment: 15th edition. Brooks/Cole, Belmont, CA, 2007.“Population by region” Digital Image. The Sustainable Scale Project. 2003. The Santa-Barbara Family Foundation. 11 January,

2009. http://www.sustainablescale.org/AreasofConcern/Population/PopulationandScale/QuickFacts.aspx“Population growth” Digital Image. The Sustainable Scale Project. 2003. The Santa-Barbara Family Foundation. 11 January, 2009.

http://www.sustainablescale.org/AreasofConcern/Population/PopulationandScale/QuickFacts.aspx"Rank Order - Total Fertility Rate." CIA - The World Fact Book. 18 Dec 2008. Central Intelligence Agency. 11 Jan 2009

<https://www.cia.gov/library/publications/the-world-factbook/rankorder/2127rank.html>.