Global Ecology

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Global Ecology
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Outline

• Atmospheric Envelope
• Greenhouse Effect
• El Nino
• Effects
• Tropical Deforestation
• Human Influence on Atmospheric Composition
• Depletion and Recovery of the Ozone Layer

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Atmospheric Envelope

• Clean, dry air at the earths surface is approx
• 78.08 Nitrogen
• 20.94 Oxygen
• 0.93 Argon
• .003 Carbon Dioxide
• .00005 Ozone
• Water vapor and trace elemental gases (Ne,
  Methane)

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Atmospheric Envelope

• Troposphere- earth surface to 9-16 km
• Stratosphere- from troposphere to 50 km
• Atmosphere modifies earths environment
• i.e ozone in Atm. reduces amount of UV light
• Also helps keep the earth surface warm-
  greenhouse effect

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Greenhouse Effect

• Heat is trapped near the earths surface by
  greenhouse gases
• (Water Vapor, Carbon Dioxide, Methane, Ozone,
  Nitrous Oxide, and CFCs)
• Absorb infrared and reemit most back to earth.
• 30 Solar energy reflected back by clouds,
  particulate matter, etc.
• 70 Absorbed by atmosphere/surface.

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Greenhouse Effect
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A Global SystemThe El Nino Southern Oscillation,
a large-scale atmospheric and oceanic phenomenon,
influences ecological systems on a global scale.
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• During El Nino, a warm current appears off the
  coast of Peru.
• Generally during Christmas season (El Nino refers
  to the Christ child).
• Southern Oscillation refers to oscillation in
  atmospheric pressure that extends across the
  Pacific Ocean.
• El Nino animation
• Beginning El Nino
• Peru during El Nino
• Recovery of El Nino

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El Nino Today

• During mature phase, the sea surface in eastern
  tropical Pacific is much warmer than average and
  barometric pressure over the eastern Pacific is
  lower than average.
• Promotes formation of storms over eastern
  Pacific, and increased precipitation to much of
  North America.

El Nino and La Nina video
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El Nino Today

• During El Nino, sea surface in western Pacific is
  cooler than average and barometric pressure is
  higher than average.
• Produces drought over western Pacific.
• La Nina Periods of lower sea surface
  temperatures and higher than average pressure in
  eastern tropical Pacific.
• Drought to much of North America.
• Higher than average precipitation in western
  Pacific.

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El Nino and Marine Populations

• Under average conditions, coastal waters are
  relatively cool along most of the east coast of
  S. America.
• Tongue of cool water extends westward.
• Cool water brought to surface by upwelling.
• During mature phase, warm surface water shuts
  off, reducing nutrient supply, and reducing
  phytoplankton production.
• Reproductive failure, migration, death.

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El Nino and Great Salt Lake

• Strong El-Nino of 1982-83 was source of many
  storms deep into interior of N. America.
• Increased precipitation with Great Salt Lake
  basin.
• 1983-87 lake rose 3.7 m.
• Wurtsbaugh and Smith Berry found lake salinity
  dropped by 50 g/l and the lake was invaded by
  predaceous insect Trichocorixa verticalis.

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El Nino and Great Salt Lake

• Predator reduced population of brine shrimp from
  12,000 to 74 per m3.
• Phytoplankton biomass increased significantly.
• By 1990, lake level fell 2.8 m, and salinity
  returned to 100 g/l.
• All ecosystem changes were reversed.

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El Nino and Kangaroo Populations

• Red Kangaroo (Macropus rufus) occupies most of
  Australias semiarid interior.
• During wet period with plenty of food, females
  will simultaneously have a joey (juvenile)
  following, a younger offspring in the pouch, and
  an embryo waiting to enter the pouch.
• Under marginal conditions, most young die soon
  after leaving the pouch.
• If food becomes scarce, females stop lactating
  and young die in embryo stage.

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El Nino and Kangaroo Populations

• Kangaroos breed quickly and young enter the pouch
  within 60 days of onset of significant rainfall.
• By reproducing large numbers of offspring under
  favorable conditions, kangaroos increase the
  number of adults that will face El Nino induced
  droughts.
• Cairns and Grigg found a tight coupling of M.
  rufus populations to El Nino.

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Human Activity and Global Nitrogen Cycle

• As human civilization developed intensive
  agriculture and industrial processes, we began to
  manipulate nitrogen cycle on massive scale.
• Vitousek
• N - fixing bacteria/plants 100 Tg/yr
• Marine environments 5-20 Tg/yr
• Lightning 10 Tg/yr
• Human sources 130 Tg/yr

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Tropical Deforestation

• Support at least half of earths species.
• Skole and Tucker reported tropical forests occur
  in 73 countries and once covered 11,610,360 km2.
• Brazil contains 1/3 of total.
• Highest deforestation rate.
• Estimated by 1978, 78,000 km2 deforested.
• Annual rate of deforestation 1978-1988 was 15,000
  km2.

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Tropical Deforestation
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Edge Effects and Tropical Deforestation

• When a forest fragment is isolated due to
  cutting, its edge is exposed to greater amounts
  of solar radiation and wind.
• Physical environment along forest edges is hotter
  and drier and solar intensity is higher.
• Fragmentation decreases diversity of many animal
  groups.

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Edge Effects and Tropical Deforestation
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Human Influence on Atmospheric Composition

• Record of atmospheric composition during last
  160,000 years was extracted from ice cores in
  Greenland and Iceland.
• Samples of atmosphere trapped in ice.
• Core indicated two very large fluctuations in
  atmospheric CO2 concentrations.
• 140,000 years ago.
• 13,000 years ago.

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Human Influence on Atmospheric Composition
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Human Influence on Atmospheric Composition

• Periods of low CO2 correspond to low temperatures
  experienced during ice ages, while high levels
  correspond to interglacial periods.
• During 19th and 20th centuries, concentration of
  atmospheric CO2 increased dramatically.

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Human Influence on Atmospheric Composition

• Fossil fuel burning alone produces more than
  enough CO2 to account for recent atmospheric
  concentrations.
• Three major periods of interruptions
• World War I
• Great Depression
• World War II

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Depletion and Recovery of the Ozone Layer

• In 1985, British Antarctic Survey discovered
  major reduction in atmospheric ozone (O3) in
  stratosphere.
• Ozone absorbs potentially harmful UV or radiation
• Attention focused on stopping chlorofluorocarbons
  (CFCs).
• 1987 Montreal Protocol
• Largest hole to date in 2000.
• 2003 saw first reported evidence the ozone layer
  is recovering.

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