Global Ecology
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Outline
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Atmospheric Envelope
Greenhouse Effect
El Nino
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Effects
Tropical Deforestation
Human Influence on Atmospheric Composition
Depletion and Recovery of the Ozone Layer
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Atmospheric Envelope
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Clean, dry air at the earth’s surface is approx:
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78.08 %
20.94 %
0.93 %
.003 %
.00005 %
Nitrogen
Oxygen
Argon
Carbon Dioxide
Ozone
Water vapor and trace elemental gases (Ne,
Methane)
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Atmospheric Envelope
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Troposphere- earth surface to 9-16 km
Stratosphere- from troposphere to 50 km
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Atmosphere modifies earth’s environment
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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
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Heat is trapped near the earth’s surface by
greenhouse gases:
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(Water Vapor, Carbon Dioxide, Methane, Ozone,
Nitrous Oxide, and CFC’s)
Absorb infrared and reemit most back to
earth.
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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 System
The 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.
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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
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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.
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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
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During El Nino, sea surface in western Pacific
is cooler than average and barometric
pressure is higher than average.
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Produces drought over western Pacific.
La Nina: Periods of lower sea surface
temperatures and higher than average
pressure in eastern tropical Pacific.
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Drought to much of North America.
Higher than average precipitation in western
Pacific.
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El Nino and Marine Populations
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Under average conditions, coastal waters are
relatively cool along most of the east coast of
S. America.
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Tongue of cool water extends westward.
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Cool water brought to surface by upwelling.
During mature phase, warm surface water shuts
off, reducing nutrient supply, and reducing
phytoplankton production.
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Reproductive failure, migration, death.
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Strong El-Nino of 1982-83 was source of many
storms deep into interior of N. America.
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Increased precipitation with Great Salt Lake basin.
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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.
El Nino and Great Salt Lake
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El Nino and Great Salt Lake
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Predator reduced population
of brine shrimp from 12,000
to 74 per m3.
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Phytoplankton biomass
increased significantly.
By 1990, lake level fell 2.8 m,
and salinity returned to 100
g/l.
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All ecosystem changes were
reversed.
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El Nino and Kangaroo Populations
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Red Kangaroo (Macropus rufus) occupies
most of Australia’s 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
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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
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As human civilization developed intensive
agriculture and industrial processes, we
began to manipulate nitrogen cycle on
massive scale.
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Vitousek
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N - fixing bacteria/plants
Marine environments
Lightning
Human sources
100 Tg/yr
5-20 Tg/yr
10 Tg/yr
130 Tg/yr
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Tropical Deforestation
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Support at least half of earth’s species.
Skole and Tucker reported tropical forests
occur in 73 countries and once covered
11,610,360 km2.
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Brazil contains 1/3 of total.
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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
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When a forest fragment is isolated due to
cutting, its edge is exposed to greater
amounts of solar radiation and wind.
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Physical environment along forest edges is hotter
and drier and solar intensity is higher.
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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
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Record of atmospheric composition during
last 160,000 years was extracted from ice
cores in Greenland and Iceland.
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Samples of atmosphere trapped in ice.
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Core indicated two very large fluctuations in atmospheric
CO2 concentrations.
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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
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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
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Fossil fuel burning alone produces more than
enough CO2 to account for recent atmospheric
concentrations.
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Three major periods of interruptions:
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World War I
Great Depression
World War II
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Depletion and Recovery of the Ozone
Layer
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In 1985, British Antarctic Survey discovered
major reduction in atmospheric ozone (O3) in
stratosphere.
Ozone absorbs potentially harmful UV or
radiation
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Attention focused on stopping chlorofluorocarbons
(CFCs).
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1987 Montreal Protocol
Largest hole to date in 2000.
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2003 saw first reported evidence the ozone layer is
recovering.
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