Human Impact on the Biosphere

1
Human Impact on the Biosphere

• Intro to Environmental Science

2
Human Impacts

• Humans are using energy and altering the
  environment at astonishing rates
• We are altering natural processes before we even
  understand them

3
Developing vs. Developed

• In developing countries (LDCs), per capita
  resource use is fairly low but growing, as is
  population size
• In developed countries (MDCs), population growth
  has slowed but per capita resource use is very
  high

4
Pollutants

• Substances with which an ecosystem has had no
  prior evolutionary experience or adaptive
  mechanisms.
• Depends on concentration, location, and timing.

5
Air Pollutants

• Carbon oxides
• Sulfur oxides
• Nitrogen oxides
• Volatile organic compounds(VOCs)
• Photochemical oxidants
• Suspended particles

6
Industrial Smog

• Gray-air smog
• Forms over cities that burn large amounts of coal
  and heavy fuel oils mainly in developing
  countries
• Main components are sulfur oxides and suspended
  particles

7
Photochemical smog

• Brown-air to orange smog
• Forms when sunlight interacts with primary
  release chemicals
• Nitrogen oxides are major culprits
• Hot days contribute to formation as does thermal
  inversion

8
Thermal Inversion

• Weather pattern in which a layer of cool, dense
  air is trapped beneath a layer of warm air

cool air
warm inversion air
cool air
9
Acid Deposition

• Caused by the release of sulfur and nitrogen
  oxides
• Coal-burning power plants and motor vehicles are
  major sources

10
Ozone Thinning

• In early spring and summer ozone layer over
  Antarctica thins
• Seasonal loss of ozone is at highest level ever
  recorded

11
Effect of Ozone Thinning

• Increased amount of UV radiation reaches Earths
  surface
• UV damages DNA and negatively affects human
  health
• UV also affects plants, lowers primary
  productivity

12
Protecting the Ozone Layer

• CFC production has been halted in developed
  countries, will be phased out in developing
  countries
• Methyl bromide will be phased out
• Even with bans it will take more than 50 years
  for ozone levels to fully recover

13
Generating Garbage

• Developed countries generate huge amounts of
  waste
• Paper products account for half the total volume
• Recycling can reduce pollutants, save energy,
  ease pressure on landfills

14
Land Use

• Almost 21 percent of Earths land is used for
  agriculture or grazing
• About half the Earths land is unsuitable for
  such uses (non-arable)
• Remainder could be used, but at a high ecological
  cost

15
Green Revolutions

• Improvements in crop production
• Introduction of mechanized agriculture and
  practices requires inputs of pesticides,
  fertilizer, fossil fuel
• Improving genetic character of crop plants can
  also improve yields

16
Deforestation

• Removal of all trees from large tracts of land
• 38 million acres logged each year
• Wood is used for fuel, lumber
• Land is cleared for grazing or crops

17
Effects of Deforestation

• Increased leaching and soil erosion
• Increased flooding and sedimentation of
  downstream rivers
• Regional precipitation declines
• Possible amplification of the greenhouse effect

18
Regions of Deforestation

• Rates of forest loss are greatest in Brazil,
  Indonesia, Mexico, and Columbia
• Highly mechanized logging is proceeding in
  temperate forests of the United States and Canada

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Reversing Deforestation

• Coalition of groups dedicated to saving Brazils
  remaining forests
• Smokeless wood stoves have saved firewood in
  India
• Kenyan women have planted millions of trees

20
Destroying Biodiversity

• Tropical rainforests have the greatest variety of
  insects, most bird species
• Some tropical forest species may prove valuable
  to humans
• Our primate ancestors evolved in forests like the
  ones we are destroying

21
Desertification

• Conversion of large tracts of grassland to
  desertlike conditions
• Conversions of cropland that result in more than
  10 percent decline in productivity

22
The Dust Bowl

• Occurred in the 1930s in the Great Plains
• Inappropriate cultivation techniques, overgrazing
  and prolonged drought left the ground bare
• 1934 winds produced dust storms that stripped
  about 9 million acres of topsoil

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Ongoing Desertification

• Sahel region of Africa is undergoing rapid
  desertification
• Causes are overgrazing, overfarming, and
  prolonged drought
• One solution may be to substitute native
  herbivores for imported cattle

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Water Use and Scarcity

• Most of Earths water is too salty for human
  consumption
• Desalinization is expensive and requires large
  energy inputs
• Irrigation of crops is the main use of freshwater

25
Negative Effects of Irrigation

• Salinization, mineral buildup in soil
• Elevation of the water table and waterlogging
• Depletion of aquifers

26
Ogallala Aquifer

• Extends from southern South Dakota to central
  Texas
• Major source of water for drinking and irrigation
  
• Overdrafts have depleted half the water from this
  nonrenewable source

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Aquifer Problems
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Water Pollutants

• Sewage
• Animal wastes
• Fertilizers
• Pesticides
• Industrial chemicals
• Radioactive material
• Excess heat (thermal pollution)

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Wastewater Treatment

• Primary treatment
• Use of screens and settling tanks
• Addition of chlorine to kill pathogens
• Secondary treatment
• Microbes break down organic matter
• Tertiary treatment removes additional toxic
  substances rarely used

30
Water Wars?

• Per capita amount of freshwater available is
  decreasing
• International conflicts over water use and
  quality have already occurred
• Building dams or dumping pollutants effect
  countries downstream

31
Energy Use

• Only 10 percent of energy used in developed
  countries is from renewable sources
• Less developed countries rely more heavily on
  renewable sources (primary biomass)

32
Fossil Fuels

• Coal, oil, natural gas
• Main energy source of developed countries
• Burning of fossil fuels contributes to global
  warming

33
Oil

• Reserves are declining
• Many reserves are in ecologically fragile
  wilderness areas
• Environmental costs of extracting and
  transporting reserves from such areas are high

34
Coal

• Extensive reserves exist
• Mining is very destructive
• Burning coal releases sulfur dioxides that cause
  acid deposition

35
Nuclear Energy

• Used extensively in some energy-poor developed
  countries
• Little support in the United States
• Emits fewer air pollutants than burning coal, but
  creates radioactive wastes
• Potential for meltdown

36
Chernobyl Accident - 1986

• Core meltdown at a nuclear power plant in the
  Ukraine
• 31 immediate deaths, radiation sickness and death
  for others
• Cloud of radiation spread by winds across Europe
• Long-term health impacts downwind

37
Solar-Hydrogen Energy

• Photovoltaic cells use sunlight energy to split
  water
• Hydrogen gas produced in this way can be used as
  fuel or to generate electricity
• Clean, renewable technology

38
Wind Energy

• An indirect use of solar energy
• Wind farms are arrays of turbines
• Can supplement needs of some regions but is not
  dependable enough on it own

39
Fusion

• Energy is released when atomic nuclei fuse
• This process produces solar energy
• Attempts to mimic this process on Earth require
  use of lasers, magnetic fields
• Not yet a commercially viable energy source

40
Changes in the World of Life

• Adaptations of species have changed the
  environment
• Photosynthetic organisms that arose during the
  Proterozoic altered the atmosphere by adding
  oxygen
• Change is natural

41
Humans and Change

• Unlike previous species, human have the capacity
  to observe and make decisions about the changes
  they bring about

42
The Big Picture
Environment
Economics
Socio-politics
43
References

• Modified from presentation of Prentice Hall
  Publishers, 2002