week 5: human population as environmental factor supplement—latitude and...

Week 5:Week 5:Human population as environmental Human population as environmental

factorfactor

• Supplement—Latitude and LongitudeSupplement—Latitude and Longitude• Chapter 5 B&KChapter 5 B&K

• Rates of growthRates of growth• The prophecy of Malthus and quality of lifeThe prophecy of Malthus and quality of life• Population growth and exponential growthPopulation growth and exponential growth• The logistic growth curve and human populationThe logistic growth curve and human population• Limiting factorsLimiting factors• Age StructureAge Structure• Fertility rates and life expectancy Fertility rates and life expectancy • Controlling population growthControlling population growth

Ward Island as a SystemWard Island as a System

Shape of the EarthShape of the Earth

We think of the earth as a sphere

It is actually a spheroid, slightly larger in radius at

the equator than at the poles

Cutting Plane of a MeridianCutting Plane of a Meridian

P

Meridian

Equator

plane

Prime Meridian

Definition of Longitude, Definition of Longitude,

0°E, W

90°W(-90 °)

180°E, W

90°E(+90 °)

-120°

-30°

-60°

-150°

30°

-60°

120°

150°

= the angle between a cutting plane on the prime meridianand the cutting plane on the meridian through the point, P

P

Definition of Latitude, Definition of Latitude,

(1) Take a point S on the surface of the ellipsoid and define there the tangent plane, mn(2) Define the line pq through S and normal to thetangent plane(3) Angle pqr which this line makes with the equatorialplane is the latitude , of point S

O

Sm

nq

p

r

Latitude and Longitude on a Latitude and Longitude on a SphereSphere

Meridian of longitude

Parallel of latitude

X

Y

ZN

EW

=0-90

°S

P

OR

=0-180°E

=0-90°N

•

Greenwichmeridian

=0°

•

Equator =0°

•

•=0-180°W

- Geographic longitude - Geographic latitude

R - Mean earth radius

O - Geocenter

Earth to Globe to MapEarth to Globe to Map

Representative Fraction

Globe distanceEarth distance

=

Map Scale: Map Projection:

Scale Factor

Map distanceGlobe distance

=

(e.g. 1:24,000) (e.g. 0.9996)

Definition of ElevationDefinition of Elevation

Elevation Z

•

Pz = zp

z = 0

Mean Sea level = Geoid

Land Surface

Elevation is measured from the Geoid

Cylindrical ProjectionsCylindrical Projections(Mercator)(Mercator)

Transverse

Oblique

Longitude was a major problem of Longitude was a major problem of the 1700’sthe 1700’s

• Although the shape of the world was reasonably well known, and latitude could be calculated from the angle of the sun at noon, mariners could not calculate their longitude.

• The British government offered a huge prize (£20,000) for a solution in 1714.

• The prize was claimed in 1760 by John Harrison, who invented the modern timepiece.

Prophecy of MalthusProphecy of Malthus

• English clergyman & economist (1766-1834) derives his “prophecy from two postula:

• First, That food is necessary to the existence of man.

• Secondly, That the passion between the sexes is necessary and will remain nearly in its present state.

The prophecyThe prophecy• Famine seems to be the last, the most dreadful

resource of nature. The power of population is so superior to the power in the earth to produce subsistence for man, that premature death must in some shape or other visit the human race. The vices of mankind are active and able ministers of depopulation. They are the precursors in the great army of destruction; and often finish the dreadful work themselves. But should they fail in this war of extermination, sickly seasons, epidemics, pestilence, and plague, advance in terrific array, and sweep off their thousands and ten thousands. Should success be still incomplete, gigantic inevitable famine stalks in the rear, and with one mighty blow levels the population with the food of the world.

Environmental ProblemsEnvironmental ProblemsWhat’s your top priority?What’s your top priority?

• Climate Change• Biodiversity• Air pollution• Water pollution• Solid waste• Loss of wilderness• Six Billion Human Beings (explore world population growth)

Total Fertility Rate (TFR)Total Fertility Rate (TFR)• The average number of children expected

to be born to a woman during her lifetime.• Note that demographers and population

scientists usually express population size as the number of females in a population and ignore males.

• How do social practices affect fertility?– For example: polygamy in Arab countries,

among early Mormans?– For example: preference for males in China?

• Six Billion Human Beings (learn about TFR)

Basic ConceptsBasic Concepts• Rates of Growth

– Growth rates—inversely related to a nation’s per capita income; positive feedback loop increasing poverty.

• Populations, Density, and Consumption (technology)– Population impact: number of people and

environmental impact per person.– Total environmental impact of a population = number

of people (population) x impact per person (Consumption & technology); raising either variable increases the total impact.

– Impact depends on consumption rates and population density.

– Dense populations have large local impact.– Consumptive populations have large global reach and

utilize vastly more resources.

Human Population ErasHuman Population Eras

• Early hunter-gatherers ~few million people.Growth rate <0.0001%

• Early agriculture – first rise of population.Growth rate ~0.03%

• Industrial revolution – improvements in health care & food supply lead to sharp increase in human population.Growth rate ~0.1%

• Today – slowing rate of population growth for Europe and U.S., rapid in Asia, Africa, South America. Growth rate 1.4-2%

Population dynamicsPopulation dynamics• The crude birthrate of a population is the

number of births per 1000 individuals in a population.

• The crude growth rate is the crude birthrate minus the crude death rate, or the net change in a population of 1000 over a year.

• Maximum lifetime is the maximum possible age for an individual of a species.

• Life expectancy is the average remaining years of an individual at a given age; it is often used to refer to the average lifespan of individuals in a population.

Quiz 5aQuiz 5a1. Assume that the rate of increase for goats is 14% per

year. At this rate, if Mr. Champini’s herd of 150 goats had not been stolen by bandits, it would have increased to how many after 5 years? a) 2,521,018; b) 200; c) 3000; d) 300; e) 600.

2. The Geographic Positioning System uses what principle to locate objects on earth? a) synchronized detection of laser pulses; b) radio signals from an array of transmitter towers; c) precise measurement of distance to satellites whose exact orbit is known; d) receivers in a series of satellites detect the GPS position and transmit it back to the user; e) position of celestial bodies such stars and planets.

3. The prophecy of Malthus predicts that human population will increase without limit until all only humans remain on Earth. a) True; b) False.

4. A major cause for population increase has been: a) rising birth rates; b) falling death rates; c) rising birth rate & falling death rate; d) improved educational; e) none of these

Differences in causes of deathDifferences in causes of death

Equations of Population ChangeEquations of Population Change

• Population sizeP2 = P1 + (B – D) + (I – E)

• Growth rateg = (B-D)/N (Births-Deaths)/Number of people

• Exponential growth & doubling timePt = P0 exponent gt

Doubling time = 70/g%

• If world growth rate is 1.75%, doubling time is 70/1.75 = 40 years

Demographic Changes Among Demographic Changes Among RegionsRegions

• Modern history is dominated by population shifts—Do consumption patterns match?

Total Fertility Rates and Pop. Total Fertility Rates and Pop. GrowthGrowth

• Population growth depends more on TFR than life expectancy.

• However, survival to child-bearing ages is a crucial factor.

• The TFR in future populations will have major impact on population growth.

Different rates, different outcomesDifferent rates, different outcomes

DemographyDemography

• Age Structure– Numbers of people and gender balance

• Demographic transition (rem logistic curve)

• Total Fertility• Population and environment• Death rate and environment• Population change and standard of living• Six Billion Human Beings (learn about age structure and survival rates)

Population structurePopulation structure

Replacement-level fertility and Replacement-level fertility and momentummomentum

• The TFR required for a population to remain constant is about 2.1 children/female.

• Even if birth rates are declining in a population, population momentum will cause population to grow after replacement-level TFR is achieved.

• Why?

Pop. Growth and the Logistic Pop. Growth and the Logistic Curve Curve

• The logistic curve predicts that growth will slow as a population approaches its carrying capacity.

• Change from increase to maintenance rates of growth called demographic transition.

• Can this information be used to predict eventual size of human population?

Demographic TransitionDemographic Transition• Note that limits to human population levels

reflect societal choices rather than limiting factors that control wildlife populations.

• What limits do affect population growth?

Demographic transitionDemographic transition

The Carrying Capacity of EarthThe Carrying Capacity of Earth

• Improving the standard of living in poor countries by traditional means may negate the benefits of controlling population growth. Why?

• Earth’s maximum sustainable human population cannot be calculated without making value judgments about the quality of life we desire for that population.

• To what degree do Earth’s populations (nations or societies) compete for resources?

Limiting FactorsLimiting Factors

  Limiting factors are those which limit population growth; they may be short-term (limiting growth within one year of occurrence), intermediate-term (limiting growth after one year but before 10 years of occurrence) or long-term (limiting growth ten or more years after occurrence).

Limiting factors cont.Limiting factors cont.   The food supply is the resource most

susceptible to constraint by short-term limiting factors.Some forms of pollution, energy shortages, desertification, and disruption in supply of renewable and non-renewable resources are examples of intermediate-term limiting factors.

• Long-term limiting factors include soil erosion, groundwater depletion, and global climatic changes and pollution effects.

  The declining per capita availability of certain biological resources suggests a human population near or beyond its current long-term carrying capacity.

Limits to GrowthLimits to Growth• Food supply:

– 1984: 346 kg per capita1994: 311 kg per capita

• Land/soil resources– Decline since 1954 to 1.7 ha per capita– Predict in 2050 1.0 ha per capita

• Water resources– 350 to 1000 l/day developed countries – 2 to 5 l/day

in developing countries• Population density source http://www.photius.com/wfb1999/rankings/population_density_0.html

– Hong Kong: 6,570 people/km2

– Netherlands: 466 people/km2

– Africa (all): 66 people/km2

– United States: 30 people/km2

ChinaChina • Population: 1.25 billion• 134 people/km2

• Birth rate: 1.5%• (U.S. 1.4%)• One-child policy • Rapid economic growth

• China is now experiencing a demographic bonus due to having a high proportion of productive adults relative to children.

• As China changes its standard of living, resource usage—particularly water use—will have a profound impact.

• Aging, gender balance and population growth will remain important issues.

• Six Billion Human Beings (Check current population size)

Quiz 5b—pg 1Quiz 5b—pg 1Choose the best suited answer to questions 1-3 from concepts a-e.

1) The s-shaped curve according to which a population grows rapidly but eventually reaches a constant population:

a) demographic transistion

2) The maximum number of a particular species that an environment can support without degradation to the environment:

b) replacement fertility curve

3) The movement of a nation from a high population growth to a low population growth:

c) logistic growth curve

d) sustainablity

e) carrying capacity

Quiz 5b—pg 2Quiz 5b—pg 2

4) The figure above illustrates which of the following concepts: a) replacement level fertility; b) population age structurec) low death rates; d) Malthus’ theory of human population; e) logistic population growth

5)Assume that the figure above illustrates the characteristics of a tribe on a small Pacific island. Which of the following is a plausible explanation for the shape of the graph: a) a devastating drought about 10 years ago; b) the arrival of a clan from another island about 20 years agoc) introduction of prenatal and infant medicine about 10 years ago; d) many of the island elderly moved to another island about 5 years ago; e) a record crop harvest about 5 years