Natural Global changes: Not a new phenomenon

• Global changes are not new : natural changes occurred in long time frames
• Climates will vary in response to Earth's motions around the Sun
• Continuity of plate tectonics and solar radiation for billions of years to come
• Ecosystems will evolve and adapt to natural changes
• Earth can function with or without human species

The new global changes: short term global changes: ~100’s of years time scale

• Faster changes than any othe time in earth history (other than extinctions)

Faster global changes: Human activity as the main cause: use of natural resources

• Standard of Living: Ever increasing need for natural resources
  • Increased need per capita
  • All aspects of use affect the rates: retrieval, production, distribution, consumption, and disposal.
  • Increased population

Natural resources: Energy and materials that are exploitable for monetary value

• Renewable commercial resources: forests, agricultural crops etc
• Non-renewable commercial resources: minerals, fossil fuels, soils etc.

Population growth: Historical perspectives

• First hominid at about 4 million years ago
• Early Homo sapiens species at aboout 400,000 years ago-minimal impact
• Modern human species at ~30,000-50,000 years ago
  • The Agriculture Revolution: agriculture and domestication of animals: The first regional impacts
  • World population at 10,000 years ago was about 10 million
  • All of human history to reach 1 billion in 1850
  • The Industrial Revolution: use of energy and production of goods
  • Population doubled in 80 years to 2 billion by 1930
  • The Technological Revolution
  • Doubled again in 45 years to 4 billion by 1975
  • by 1994 reached 5.6 billion
  • Projections to 10 billion by 2050
  • Doubling time ~ 70/ rate of growth

Population effects:

• Poor populations: Large number of small consumers, degrade the environment
• Rich populations: smaller number of big consumers, degrade the environment

Uneven distribution: Developed Vs developing nations (Overhead 2)

• 1950 - 33% of world population in developed countries
• 1993 - about 23% in developed countries
• Projections to 2025 give 16% in the developed countries

Aspects of resource consumption in human history

• Sun was the primary source of energy for the Stone age humans
• As humans developed - use of natural resources, oil, coal and natural gas in the last two millennia:
• Developed nations as major consumers
  • 25% population uses more than 75% of the global energy output
  • U.S at 6% of world poulation uses 30% of world energy

Use of Resources: Non renewable resources: fuels - coal, oil, gas

• Oil-the largest energy resource Overhead -3
• Present rate of oil consumptiom will exhaust resources in 40 years
• Coal, the second largest energy resource -provides ~1/3 of global energy
• Present rate will exhaust supplies in 200-500 years
• Non commercial fuels in third world - biomass used by 50% of world population
• consequences: deforestation, soil erosion

Renewable fuels:

• Solar: unlimited energy source
  • 10,000 times more than that used by humans each year
  • Inefficiency of photovoltaic cells
• Geothermal: almost 40 million times that of oil and gas
  • Problem: localized to plate margin areas, Japan, Mexico, etc
• Hydroelectric power: renewable but drawbacks: flooding, silting
• Nuclear Energy - based on fission of U-235. Problem with waste storage
• Nuclear energy -based on fusion
• No energy shortage - only shortage of a specific type of energy source
• Wind Power: derived by solar energy. Most of the energy is in high altitude winds
• Surface wind energy about 10% of what humans use. Local and unreliable
• Tides: very local and poor efficiency
• Fuelwood and biomass: about 14% of the energy source at present
  • Total annual biomass as energy source - 9 times the energy used.
  • Controlled harvesting can yield a significant fraction

Non renewable resources formed over geological times: Minerals and metals

• Metallic minerals: Fe, Cu, Ni, Au, Zn etc
  • Hydrothermal deposits: hot solutions flowing through rocks: sulfides
  • Magmatic mineral deposits: Cr, Fe, Pt, Ni, V, and Ti
  • Sedimentary mineral deposits; evaporites: Na, K, Ca salts
  • Placers - concentration by flowing water: concentration by density
    • Au, Pt and Sn (casseterite - SnO2)
  • Residual mineral deposits- removal of soluble material leaving residues
    • laterite (Iron oxides) and bauxite ( aluminum oxides)
  • Nonmetallic Minerals: gypsum, sodium carbonate, borax, clay, limestone etc
    • Many from evaporite deposits of lakes and oceans
  • Usable minerals localized in geography: no nation is self-suffcient for all
    • A self suffcient country can easily become an importer
  • 23% of population in industrialized world uses 75 % of resources
  • 6% U. S. Population uses more than 20 % of resources in the world
  • Economic dependence of poorer nations on mineral export

Impacts on the Land-Water system

• Close connection between land, water and the atmosphere
  • Weathering and erosion of land by water
  • Water transport of chemicals, nutrients and solid matter
  • Transport of soil by wind
  • Aerosol production on sea-surface and wind transport
  • Soil and dust transport by wind - soil from Sahara to S. America, Dust from Asia to Hawaii
  • Changes to Nile delta -Aswan Dam in 1970

  Impacts on the soil ecosystem - an important natural resource

  • anchors plants, recycles nutrients, filter water, and provide habitat for organisms
    • Land surface of the earth - 15 billion hectares
    • area covered by vegetation - 11.5 billion in
    • soil degradation due to human activities since 1945 - 17% of total

  Nature of Soil degradation

  • Water and wind erosion -physical removal, especially after loss of vegetation
  • Chemical degradation - loss of nutrients by overgrazing, waste deposition etc.
  • Physical deterioration - over compaction, water logging, leaching

  Human induced soil-land degradation: major causes

  • Overgrazing - affects 35% of all degraded land
  • Animal grazing - increase of albedo- cooling ground- descending
    • dry air- less moisture- desertification
    • Expansion of the Sahelian desert by overgrazing between 1935-70
  • Deforestation -affects 30% of degraded land
    • Fuelwood production in developing countries
    • Commercial uses of agricultures and timber in developed countries
    • imbalances the hydrologic cycle- removal of transpiration by plants
    • less rainfall-more run off-leaching of soils- degradation of land
  • Agricultural practices - 27% of all degraded land
    • Only about 13% of the planet's vegetated land is suitable for agriculture
    • Most of current soil degradation is occurring in this limited agricultural land
    • Soil erosion due to poor farming practices
    • Nutrient depletion, ground water contamination
    • Salinization- inadequate water drainage, irrigation in high salt water
  • Industrial and waste pollutants
    • Toxic and municipal wastes - particularly in developed countries
    • Acidification of soils - due to acid rain

  Human induced water degradation: Major water pollutants

  • Excess nutrients- eutrophication
    • Mainly from fertilizers (also sewage, detergents)
      • 1950 - 14 million tons fertilizer in all the world
      • 1990 - 140 million tons
    • Pesticides are responsible for 1/2 of all water pollution in US
    • Domestic activity in developed countries in developed countries: about (90%) of nitrogen and phosphorous in surface waters is anthropogenic
  • Sedimentation: introduction of soil in to water -agriculture, mining, deforestation, land development in urban areas etc.
    • 47% of river pollution and 22% lake pollution
    • 480 billion tons of soil lost in the past 20 years
    • Loss of wetland habitats, coral reefs, loss of feeding grounds for fish etc.
  • Toxic chemical pollution: Urban and industrial materials
    • PCB's, fertilizers, inorganic compounds , heavy metals
    • concentration in the upper parts of the food chain

The changing atmosphere:

• Increased emissions of anthropogenic gases during this century
• Regional and Global consequences
  • Acid deposition (Regional and continental scale)
  • Potential Global warming by greenhouse gases (global scale)
  • Ozone depletion in the stratosphere ( global scale)
  • Ozone addition to the troposphere (regional scale)

Major anthropogenic greenhouse gas additions to the atmosphere

• Carbon dioxide
  • Sources and causes
  • Direct measurement since 1957 Overhead -4
  • Records for the last 1000 years Overhead -5
  • Contributions in post industrial era -increase by 30%
  • Doubling time- about 40 years
  • present level of contribution to greenhouse effect - 60%
• Methane Overhead -6
  • Sources and causes: more than 60% flux due to human activities
  • Doubled in the past 200 years
  • present level of contribution to greenhouse effect - 15%
  • Equivalent CO2 emissions = 25
• Flourocarbons Overhead -7
  • Sources: introduced by humans
  • Long residence times - 75-150 years
  • 1000 times more powerful than CO2 for greenhouse effect
  • present level of contribution to greenhouse effect - 12%
  • Equivalent CO2 emissions for CFC-12= 16, 000
• Oxides of Nitrogen Overhead -8
  • Sources and causes: 30% of flux due to fossil fuel burning, fertilizers etc.
  • present level of contribution to greenhouse effect - 5%
  • Equivalent CO2 emissions
• Total greenhouse gas emissions in terms of CO2 emissions

Major contributors of greenhouse gases at present

• Anthropogenic greenhouse gas additions have increased the heat trapping capacity of the atmosphere 92% in the last 100 years.
  • US is the major contributor
  • Industrial and advanced technology nations and per capita production
  • Developing nations and per capita production

  The predictions of greenhouse warming for doubling of pre-industrial levels

  • Global temperature has increased by 0.3-0.6 degrees C during the last century.
    • Uncertain knowledge of cloud cover, ocean circulation etc.
    • General circulation models predict 1.9-5.2 degrees C
    • Intergovernmental Panel on Climate Change predicts 2-4 degrees C
    • National Research Council predicts 1.5-4.5 degrees C
    • Prudent choice appears to be 1-5 degrees C for a doubling of greenhouse gases

  Consequences of greenhouse warming

  • The sensitivity of the climate to equivalent doubling is to increase the average global temperature between 1 and 5 degrees C.
  • A rise of sea level is possible at these temperature increases (1- 10 meters).
    • Sea level rise due to expansion of sea water
    • 20% of world population willl be affected
  • Changes in the oceanic conveyor belt circulation if the poles are warmer
  • Changing moisture patterns - increases in high Northern latitudes and middle Southern latitudes
  • Decrease in many food growing areas on all continents
  • Positive feed back effects affecting the temperature increase include release of more methane as the tundra melts, increased evapopration.