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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 earth’s 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 earth’s 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 earth’s surface by greenhouse gases: (Water Vapor, Carbon Dioxide, Methane, Ozone,

Nitrous Oxide, and CFC’s) Absorb infrared and reemit most back to

earth. 30 % Solar energy reflected back by clouds,

particulate matter, etc. 70 % Absorbed by atmosphere/surface.

66Greenhouse 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.

1717El 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 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 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 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

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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