Population models and the human population

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Population models and the human population  

• By the end of this lecture you should be able to
• Provide a functional definition of a population.
• Concepts and terms spatially related,
  inter-fertile
•  Contrast exponential and logistic models for
  population growth.
• Concepts and terms intrinsic rate of increase,
  rate of change, carrying capacity
•  Describe density-dependent and
  density-independent mechanisms regulating
  population growth.

• Discuss the size and growth rate of the human
  population.
• Describe the transitions in population growth for
  developed nations.
• Discuss the relationship between the size of the
  human population and global net primary
  production.
• Discuss K for humans
• Assigned reading Chap. 52

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Exponential growth dN/dt (birth rate death
rate) N (birth rate death rate) r
where r is the intrinsic rate of
increase So, dN/dt rN, or Nt
Noert when growth rate is a function of size,
things grow exponentially. Notice, r is constant.
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Logistic growth dN/dt r N K-N/K
this last term represents the unutilized
capacity for growth If we rewrite the
equation dN/dt r K-N/K N everything
in the brackets is now analogous to the r of
the exponential growth model, but now r changes
with population size and K instead of being
constant.
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• Regulation of population size
• Decreased fecundity at high population density
• Decreased vigor and survivorship at high
  population density crowdinghormonal
  imbalancechange in fertility rates, etc.
• Abiotic factors (temperature, etc) can control
  population size
• Population cycles
• Resource availability

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http//antwrp.gsfc.nasa.gov/apod/image/0011/earthl
ights_dmsp_big.jpg
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Regional population patterns Population density
Consortium for International Earth Science
Information Network.
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Thomas Malthus (1798)
An Essay on the Principle of Population

• Populations grow geometrically while supporting
  resources grow arithmetically
• Population, if not purposefully checked
  (preventative checks), would outpace resources
  and lead to unplanned positive checks that
  would return population to sustainable levels

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HUMAN POPULATION GROWTH
Earth's population 6 billion (Oct 12, 1999)
Every second, five people are born and two people
die, a net gain of three people.
Every day, 250,000 2 x Champaign-Urbana
This year, 87,000,000 Mexico
This decade 1,000,000,000 China
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Resident population of the US 300,172,082
(288,474,753) World population 6,555,894,608
(6,255,454,008) US Census Bureau report for
Thursday 10 November, 302 pm http//www.census.g
ov/ipc/www/clock.html
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• Populations in transition (developed nations)
• High birth and death rate, little pop growth
• High birth rate but declining death rate, rapid
  growth
• Birth rate declines, pop growth declines

Graphics from U. Maryland, Dept. Meteorology
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The Global Biosphere (September 97 - August 98)
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• Prior to human impact, NPP was about 150 billion
  tons of organic matter per year.
• Humans have destroyed about 12 of the
  terrestrial NPP, and use or co-opt additional
  27.
• Thus we have already appropriated about 40 of
  the terrestrial food supply
• If we appropriate ALL of the terrestrial food
  capacity, the planet could support 15 billion

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Billions of people
GlobalCarrying Capacity
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POPULATION AND AVAILABILITY OF
RENEWABLE RESOURCES
Total
Per Capita
1990
2010
Change ()
Change ()
Population (millions)
5,290
7,030
33
Fish Catch (million tons)
85
102
20
-10
Irrigated Land
237
277
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-12
(million hectares)
Cropland (million hectares)
1,444
1,516
5
-21
Rangeland and Pasture
3,402
3,540
4
-22
(million hectares)
Forests (million hectares)
3,413
3,165
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Source Postel, S. "Carrying capacity Earth's
bottom line." State of the World, 1994.
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https//www.cia.gov/cia/publications/factbook/rank
order/2119rank.html
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Forecasted probability that population will start
to decline at or before the indicated date. Lutz
et al. Nature 412, 543 - 545 (2001)
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Forecasted distributions of world population
sizes (fractiles). For comparison, the United
Nations medium scenario (white line), and 95 per
cent interval as given by the NRC11 on the basis
of an ex post error analysis (vertical line in
2050) are also given. Lutz et al. Nature 412, 543
- 545 (2001)
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U.N. Conference on Population (Cairo, 1994)
"Programme of Action" (182 nations)
Goal to stabilize human population at 7.8
billion by 2050.
1. Provide universal access to family-planning
and reproductive health programs. 2. Recognize
that environmental protection and economic
development are not necessarily antagonistic.
Promote free trade, private investment and
development assistance. 3. Make women equal
participants in all aspects of society - by
increasing women's health, education, and
employment. 4. Increase access to education.
Provide information and services for adolescents
to prevent unwanted pregnancies, unsafe abortion,
and the spread of AIDS and sexually transmitted
diseases. 5. Ensure that men fulfill their
responsibility to ensure healthy pregnancies,
proper child care, promotion of women's worth and
dignity, prevention of unwanted pregnancies, and
prevention of the spread of AIDS and sexually
transmitted diseases.