Global Ecology

1 Atmospheric Envelope Clean, dry air at the earth’s surface is approx: – % Nitrogen – % Oxygen – 0.93 % Argon –.003 % Carbon Dioxide – % Ozone

2 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.

3 Greenhouse Effect

4 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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6 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.

7 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.

8 El Nino and Marine Populations

9 El Nino and Great Salt Lake Strong El-Nino of was source of many storms deep into interior of N. America. – Increased precipitation with Great Salt Lake basin 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 m 3. – Phytoplankton biomass did what? By 1990, lake level fell 2.8 m, and salinity returned to 100 g/l… All ecosystem changes were reversed.

10 El Nino and Great Salt Lake Predator reduced population of brine shrimp from 12,000 to 74 per m 3. – Phytoplankton biomass increased significantly. By 1990, lake level fell 2.8 m, and salinity returned to 100 g/l. – All ecosystem changes were reversed.

11 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/plants100 Tg/yr Marine environments5-20 Tg/yr Lightning10 Tg/yr Human sources130 Tg/yr

12 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 km 2. – Brazil contains 1/3 of total. – Highest deforestation rate. – Estimated by 1978, 78,000 km 2 deforested. – Annual rate of deforestation was 15,000 km 2.

13 Tropical Deforestation

14 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.

15 Edge Effects and Tropical Deforestation

16 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 CO 2 concentrations. – 140,000 years ago. – 13,000 years ago.

17 Human Influence on Atmospheric Composition

18 Human Influence on Atmospheric Composition

19 Human Influence on Atmospheric Composition – Fossil fuel burning alone produces more than enough CO 2 (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

20 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 saw first reported evidence the ozone layer is recovering.

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