AP Environmental Science Unit 9 Cheatsheet: Global Change

Why ozone matters: Stratospheric ozone absorbs UV radiation, protecting life on Earth from skin cancer and cataracts.

Causes of depletion:

• Anthropogenic: CFCs (chlorofluorocarbons) from refrigerants, aerosols
• Facilitator (not a cause): polar stratospheric ice clouds form in the cold, dark Antarctic winter and provide surfaces that convert chlorine reservoir compounds from CFCs into reactive Cl, which destroys ozone when sunlight returns in spring

Effect of depletion: More UV rays reach Earth's surface → increased human health risks.

Mitigation: Replace CFCs with HFCs (hydrofluorocarbons), though some HFCs are potent greenhouse gases.

Cause: Increased atmospheric greenhouse gases trap heat; oceans absorb ~90% of excess heat.

Effects on marine species:

• Habitat loss (e.g., coral reefs, kelp forests)
• Metabolic changes (altered growth, energy use)
• Reproductive disruption (spawning timing, success)

Coral bleaching: Warming causes corals to expel symbiotic algae → white appearance. Some recover; many die.

HIPPCO—six main drivers:

• Habitat destruction
• Invasive species
• Population growth
• Pollution
• Climate change
• Over-exploitation

Habitat fragmentation: Large habitats broken into isolated patches (roads, agriculture, logging). Impact varies by species.

Climate-driven habitat loss: Temperature, precipitation, and sea level changes alter suitable ranges.

Domestication impact: Managed species (honeybees, livestock) can reduce wild biodiversity.

Mitigation: Protected areas, habitat corridors, sustainable land use, habitat restoration.