Topic 8: Human Populations

consequences of exponential growth

• increased demand for food/water/land

• demand for food → raising livestock → deforestation

• loss of habitat endangers species

• loss of forest degrades air/water quality

• congested areas promote spread of disease

• more pollutants released

• more waste generated

crude birth rate (CBR)

number of live births per 1,000 people in a population per year

CBR = births / population \* 1,000

crude death rate (CDR)

number of live deaths per 1,000 people in a population per year

CDR = deaths / population \* 1,000

natural increase rate (NIR)

rate of population growth, not accounting for immigration of emigration; percentage

NIR = (CBR - CDR) / 10

doubling time (DT)

time (years) for a population to double

DT = 70 / NIR

replacement level fertility

the number of children a couple must have to replace them (2.1)

total fertility rate (TFR)

estimate of the average number of children a woman will have per year, if she passes through her childbearing years conforming to the age-specific fertility rates of a given year

TFR > replacement level

population growth

TFR < replacement level

zero/negative growth

contributing factors to total fertility rate (TFR)

• urbanization

• increasing opportunities for women

• reduce infant mortality rate

• delay women’s age when she first gives birth

• pensions for retirees

• availability of abortions & birth control

• avoiding dogmatic religion & tradition statutes

factors that reduce death rates:

• urbanization (more resources/medicine)

• better healthcare

• increased access to food

• sanitation and potable water

first stage of the demographic transition model (DTM)

• ex: a few remote groups

• CBR: high

• CDR: high

• increase: stable/slow

• reasons for changing birth rate:

  • children work

  • high infant mortality rate

  • religion/societal pressures

  • no family planning resources

• reasons for changing death rate:

  • disease/famine

  • little to no medical care

second stage of the demographic transition model (DTM)

• ex: Egypt, Kenya, India

• CBR: high

• CDR: falling rapidly

• increase: rapid

• reasons for changing birth rate:

  • children work

  • high infant mortality rate

  • religion/societal pressures

  • no family planning resources

• reasons for changing death rate:

  • medical care

  • good water/sanitation

  • more children live

third stage of the demographic transition model (DTM)

• ex: Brazil

• CBR: falling

• CDR: falls slowly

• increase: slower

• reasons for changing birth rate:

  • more medicine/food

• reasons for changing death rate:

  • medical care

  • good water/sanitation

  • more children live

fourth stage of the demographic transition model (DTM)

• ex: US, Japan, UK

• CBR: low

• CDR: low

• increase: stable/slow

• reasons for changing birth rate:

  • urbanization

  • healthcare

  • family planning

• reasons for changing death rate:

  • healthcare

  • reliable food source

age-gender pyramids

shows the proportion of the population, by sex, at each for different age levels

How do predictions made about population growth by age structure diagrams influence economic decisions?

• pensions

• social security

• job competition

• more people = more consumers = greater need for jobs

• large population provides a taxable base for supporting retirees

• more people = greater environmental footprint

factors contributing to population growth

• universal access to family planning

• better healthcare for pregnant women/children

• equality- more opportunities for women

• increased access to education

• increased involvement in child-rearing for men

• eradicate poverty

• sustainable use of natural resources

• cultural attitudes about family size

• government policies

abiotic factors

• light

• temperature

• nutrient level

biotic growth factors

• high reproductive rates

• generalized niche

• adequate food supply

• suitable to habitat

• ability to compete for resources

• ability to hide/defend from predators

• ability to migrate/live in other habitats

• ability to adapt to environmental change

biotic decrease factors

• low reproductive rate

• specialized niche

• inadequate food supply

• unsuitable/destroyed habitat

• too many competitors

• can’t run/hide from predators

• can’t resist disease/parasites

• can’t migrate

• can’t adapt to environmental change