Population growth and sustainability

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Population growth and sustainability

• Outline
• Human population growth
• Sustainability
• Harvesting resources
• Farming
• Forestry
• Fisheries
• Readings Chapters 27

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Human population, 1 A.D. 2000 A.D.
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Using the same starting and ending points, the
figure above illustrates what human population
growth would look like if it followed the
logistic growth model dN/dt rN (K-N)/Kor the
exponential growth model (dN/dt rN).
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Natural capital

• Range of natural resources provided by
  ecosystems
• air, water, soil, nutrients, forests, grasslands,
  etc.

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Simple model of resource use
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The fate of non-renewable resources
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Wastes, by-products
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Feeding humanity agriculture

• 30,000 edible plant species
• 90 of food supply is dominated by only 15 plant
  and 8 animal species
• Wheat, rice and corn 80 of all cereal crops
  consumed
• Two main forms traditional vs. industrialized

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Swidden agriculture
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Monoculture Farming
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Phytophthora infestans, late blightFungal
agent that caused the Irish Potato blight of the
mid-19th Century

• Introduced to Ireland in the 1840s, where
  potatoes (an exotic species that had become
  critical to the countrys food supply) were grown
  in dense monocultures.
• Destroyed plants in the field (above left) and
  also potatoes held in storage (above right)
• Thirteen percent of the Irish population died of
  starvation another 20 emigrated to the United
  States

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Parasitic mites are a major threat to monoculture
fish farms, and to nearby populations of wild fish
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Number of pesticide-resistant arthropods(Known
to be resistant to at least one pesticide)
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Apr. 14, 1935 Black Sunday
During the 1930s, severe droughts resulted in
crop failure, wind erosion of soil, and massive
dust storms. Thousands of families emigrated
from the region during the time of the Great
Depression.
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Algal blooms
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Salinization
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A salt desert in Tunisia
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The mechanization of agriculture has greatly
increased food production
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• Large-scale sustainable agriculture
• Soil conservation methods
• Reduction in use of pesticides
• Alternative sources of soil nutrients
• Water conservation and protection

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Permaculture
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Sustainable forestry?

• 35 of Earths surface covered by forest
  ecosystems
• Provide fuel, building materials, shelter
• Plantations but 90 of global forest resources
  harvested from native forests

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Feeding humanity fisheries

• 80 of fish catch comes from oceans and lakes

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Pacific sardine
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