Ch' 27 Human Impact on Earth Resources

1
Ch. 27 Human Impact on Earth Resources

• As any population increases, its demand for
  natural resources increases as well.
• Any type of organis can have an impact on its
  environment if its population becomes large
  enough.
• A population growth is the increase in the size
  of a population over time.
• An initial population is small until the number
  of reproductive adults increases. This will
  cause the population of that organism to increase
  rapidly if there are enough resources to continue
  the growth.
• Exponential Growth a pattern of growth in which
  a population grows faster as it increases in
  size. This causes a population explosion.
• Fig. 27-3 (pg. 713)

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• Most populations wouldnt be able to continue in
  an exponential growth pattern because of the lack
  of resources.
• What organisms may have a higher success rate?
  How about lower?
• Carrying capacity the number of organisms that
  any given environment can support.
• If a population hasnt reached its carrying
  capacity there will continue to be more births
  than deaths.
• Once the carrying capacity is reached then the
  population is at equilibrium an the number of
  births and deaths equal out.

3

• Density-independent factors are environmental
  factors that affect population growth.
• Ex. Droughts, floods, storms, pollution
• These factors affect any population regardless of
  size.
• Density-dependent factors increasingly affect a
  population as the populations size increases.
• Ex. Disease, parasites, and lack of food.
• Human Population Growth is still in the
  exponential growth stage and may continue to grow
  for at least another 50 years.
• It hasnt reached its carrying capacity.
• The current rate of growth clearly cannot
  continue forever. A demand for resources will
  continue to increase steadily.

4
Human Impact on Land Resources

• An average person in North America consumes a
  renewable yield of approximately 12 acres of
  forest and farmland.
• Mining by surface and subsurface has big affects
  on the environment. The government requires
  mining companies to restore the ground to its
  original contours and replant vegetation in the
  process of reclamation.
• Biodiversity (wide variety of species) is
  important in maintaining a stable ecosystem for
  organisms to live in.
• Monocultures of one specific crop makes it easy
  for farmers but provides risks in the form of
  plant specific diseases, pests, and fungi.

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• Pesticides are helpful to farmers by eliminating
  insects, but there are drawbacks.
• A lot of pesticides kill pollinating and
  decomposers (beneficial) insects.
• Insects reproduce quickly which cause them to
  build resistance to pesticides.
• The runoff and wind may carry pesticides to
  rivers, lakes, streams which causes harm to other
  organisms.
• Crop rotation is an excellent way for farmers to
  keep topsoil fertile. Instead of adding
  artificial fertilizers
• Farmers rotate their crops with clover, alfalfa,
  or other crops that are great nitrogen fixers and
  put nutrients back into the ground.

6

• A big reason topsoil is lost is due to
  deforestation the clearing of forested land.
• 70 of North Americans live in a urban or
  suburban area.
• The expansion of urban areas has a huge effect on
  the environment. The effect is a loss of natural
  habitats for a balanced environment.
• A lot of the global warming increase may be due
  to expansions of urban areas.
• This wipes out plants for release of oxygen.
• Pavement reflects more light less rainfall is
  absorbed.
• More greenhouse gases are released.
• More solid wastes produced.
• These wastes are leaking from landfill as toxins.

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• Lots of techniques have been implemented to
  decrease the hazards caused from urban expansion.
• Barriers for landfills.
• Wetlands are recognized and protected.
• Contaminated soils are removed and toxic
  chemicals are destroyed from the soils with heat.
• Bioremediation is a technique to treat
  contaminated soils with bacteria that eat toxic
  materials and convert them to less-harmful
  substances.

8
Human Impact on Air Resources

• Smog photochemical haze triggered by solar
  radiation reacting with hydrocarbons and nitrogen
  oxides (car exhausts).
• Ozone is the major chemical (3 oxygen atoms) in
  smog.
• Ozone is helpful in the upper atmosphere for
  filtering out harmful U.V. light.
• When ozone combines with air pollutants it
  harmful to eyes, noses, throats, lungs, and
  plants.
• Pollution can be in the form of particulate
  matter. Dust, pollen, ash, and asbestos fibers.
• They cause breathing difficulties and lung
  diseases.

9

• Humans have a major effect on air pollution with
  global warming, ozone depletion, and acid
  precipitation.
• Global Warming occurs from greenhouse effect, in
  which the average surface temperature increases.
• This is largely due to the burning of fossil
  fuels, which produce carbon dioxide as a
  bi-product.
• Since the Industrial Revolution (1850s) humans
  have been burning fossil fuels consistantly.
• Fig. 27-18 (pg.725)
• This could cause major effects on climate
  patterns.
• Glaciers melting and flooding shore lines, plant
  and animal species may not adapt well.
• Could this be a trend or are humans causing
  drastic climatic changes.

10

• CFCs from human uses was the cause of ozone
  depletion since the 1980s.
• Acid precipitation precipitation with a pH less
  than 5.
• Forms when sulfur dioxide and nitrogen oxides
  combine with atmospheric moisture.
• Coal generated by power plants produce acid
  forming gases. Scrubbers are added to the power
  plants to reduce the pollutants.
• The acid rain affects surface waters of aquatic
  ecosystems and plants and animals. The acid rain
  also damages stone buildings, statues, metal
  structures, and especial limestone structures.

11
Human Impact on Water Resources

• Freshwater is used by humans in several ways
  bathing, drinking, cooking, and washing.
• 378 billion liters of water was used per day in
  1995.
• The greatest demand on water comes from industry,
  including power plants that use water for cooling
  purposes.
• Water Pollution
• Point Sources generated pollution from a single
  point of origin, such as a sewage-treatment plant
  or an industrial site
• Nonpoint Sources generated from widely spread
  areas, such as runoff from pesticides,
  fertilizers, roads, parking lots, etc.

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• The Safe Drinking Water Act (1974) and the Clean
  Water Act (1972). These laws made water safer
  and cleaner for the ecosystem and human
  consumption. They helped reduce water pollution.
• Water Conservation
• Efficient irrigation practices, landscaping
  plants, improving delivery systems, raise water
  rates, recycle cooling water waste water for
  industries.
• Fix leaky pipes, toilets, faucets, etc.
• Efficient showerheads, toilets, outdoor watering,
  etc.