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Weiss Period 1
Global Warming Air Pollution Water Issues Species endangerment Fossil Fuels Deforestation

Saich Period 1
Global Warming Pollution Habitat Destruction Species endangerment Alternative Fuels Desertification Radio Activity

Weiss Period 2
Air Pollution Water Issues Species endangerment Alternative Energy Agricultural issues Deforestation

Saich Period 2
Global Warming Habitat Destruction Recycling Species endangerment Radio Activity Deforestation

Weiss Period 3
Global Warming Air/Soil Pollution Water Issues Species endangerment Desertification Acid Rain

Saich Period 3
Global Warming Pollution Habitat Destruction Species endangerment Alternative Energy Deforestation