Figure 9'2 Explosive Growth of the Human Population

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Figure 9.2 Explosive Growth of the Human
Population
Human population growth
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Population growth is affected by age structure
Greater fecundity mean offspring produced by a
female of age x
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(No Transcript)
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A fecundity pattern 2003-2004 data
Number alive at age x
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Human population growth and its ecological
footprint

• Ecological footprint total area of productive
  ecosystems required to support a population.
• Data from national statistics
• Population size
• Resource use
• Agricultural productivity
• Manufacture of goods
• Pollution
• E.g., amount of a food product consumed / amount
  of that product produced per unit of land area.

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• 1999 11.5 billion hectares productive land
• Average person EF 2.3 hectares
• Est. Earth could support 5 billion individuals.
• But, pop. In 1999 was 6 billion individuals.
• Resources used more rapidly then they can be
  regenerated.
• Estimated U.S. carrying capacity 186 million
  EF of 9.7 h/person
• Actual U.S. population was 279 million

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Survivorship is variable
1949-1994 data
Adequate food
Food shortage
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Dispersal Rocky Mountain News (Feb 26, 2009)
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Population dynamics, keystone species, and
control of community structure
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Metapopulations and habitat patches
10 km2 quadrats
1. All in Ohio 2. Variation in forest patches Num
ber Mean area Total area Shapes 3. Surrounded
by other ecosystem types
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Significance of patch size depends on organism
Fractal geometry developed in 1982 (Benoit
Mandelbrot) Now used to quantify dimensions of
complex shapes Size of patch depends on scale
used
1. Bald eagle nest spacing (0.782 km) perimeter
of island c. 760 km 2. Barnacle spacing (each
requires c. 2 cm of coastline perimeter of
island c. 11,000 km
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Field research on effects of patch size on
movements among three rodent species
Sigmodon Microtus Peromyscus
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Scale
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• Metapopulations disjunct conspecific populations
  linked by the movement of individuals

Snail kite
Disjunct habitat patches
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• Metapopulation patterns
• Best case scenario
• Dispersal among patches sufficiently high that
  populations are rescued from local extinctions.

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• Core-satellite pattern
• Persistence depends on one or more
  extinction-resistant (source) populations.
• Surplus individuals produced
• Maintain peripheral (sink) populations
• a pop. unable to produce
• sufficient individuals
• to maintain itself.

Low quality habitat
High quality habitat
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• Example of a metapopulation study
• Bay checkerspot butterfly
• 1987 population of 106 adult butterflies on a
  2,000 hectare habitat (Jasper Ridge, Stanford
  University).
• ha 2.471 acres or 10,000 m2
• Source population (Morgan Hill) for nine other
  populations of 10 to 350 adult butterflies on
  patches of 1 to 250 ha.

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Extinct in 1976, recolonized in1986
27 patches of suitable habitat No difference in
quality Serpentine soils
Colonized in 1986
Morgan Hill
Distance factor Poor dispersal ability
10 km
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• Glass half empty (rare species)
• Local extinctions occur during an overall
  regional decline.
• Ineffective population dispersal failure to
  rescue populations from extermination.