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Global Ecology
Atmospheric Envelope
• Clean, dry air at the earth’s surface is approx:
– 78.08 %
Nitrogen
– 20.94 %
Oxygen
– 0.93 % Argon
– .003 % Carbon Dioxide
– .00005 %
Ozone
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Greenhouse Effect
• Heat is trapped near the earth’s surface by
greenhouse gases:
– Such as???
• 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 System
• 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.
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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.
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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
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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.
• Predator reduced population of brine shrimp from
12,000 to 74 per m3.
– Phytoplankton biomass did what?
• 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 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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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
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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
• 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.
– 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
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Human Influence on Atmospheric
Composition
– Fossil fuel burning alone produces more than
enough CO2 (5,600 Tg/yr) to account for recent
atmospheric concentrations (3,500 Tg/yr).
• 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.
– 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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