Rucete ✏ AP Environmental Science In a Nutshell
9. Global Change
This unit examines global environmental changes driven by human and natural causes. Topics include ozone depletion, the greenhouse effect, climate change, ocean impacts, invasive species, endangered species, and biodiversity loss. It also explores mitigation efforts like international agreements and sustainable development strategies.
9.1 Stratospheric Ozone Depletion
Ozone Formation and Breakdown
• Ozone (O₃) forms in the stratosphere when UV radiation splits O₂ into atomic oxygen, which then bonds with O₂.
• O₃ absorbs harmful UVB and UVC radiation but is constantly formed and broken down by UV light.
Ozone Depletion
• Caused mainly by chlorofluorocarbons (CFCs) and halons, which release chlorine and bromine in the stratosphere.
• One chlorine atom can destroy over 100,000 ozone molecules.
• Depletion first noticed over Antarctica; CFCs persist ~200 years in the atmosphere.
Effects
• Increased skin cancer, cataracts, immune suppression.
• Reduced crop yields and phytoplankton growth.
• Disruption of food webs and DNA damage from increased UV radiation.
9.2 Reducing Ozone Depletion
Strategies
• Ban or phase out CFCs and halons (e.g., Montreal Protocol).
• Use alternative coolants (e.g., ammonia, propane, helium).
• Provide rebates for replacing old appliances and restrict ozone-depleting aerosol use.
• Limit HCFCs, which are less harmful than CFCs but still potent greenhouse gases.
9.3 The Greenhouse Effect
Mechanism
• Greenhouse gases absorb and re-radiate infrared heat from Earth’s surface, warming the atmosphere.
• Key gases: CO₂, CH₄, N₂O, water vapor, CFCs, and fluorinated gases.
Anthropogenic Contributions
• Fossil fuel combustion, deforestation, agriculture, and industry increase GHG emissions.
• Oceans absorb ~25% of CO₂ but warming decreases their absorption capacity (positive feedback loop).
9.4 Increase in Greenhouse Gases
Evidence of Increase
• Mauna Loa Observatory shows steady CO₂ rise since the 1950s.
• Ice core data reveal historical CO₂ concentrations tied to temperature over thousands of years.
Consequences
• Rising global temperatures, melting ice sheets and glaciers.
• Sea level rise from thermal expansion and melting land ice.
• More frequent extreme weather: droughts, floods, hurricanes, heatwaves.
• Ocean warming and acidification harm coral reefs and fisheries.
Feedback Loops
• Positive: melting ice reduces albedo → more heat absorbed → more melting.
• Negative: increased vegetation growth removes more CO₂ from the atmosphere.
9.5 Climate Change
Impacts on Ecosystems
• Habitat shifts, species migration, disrupted food webs.
• Coral bleaching due to warming and acidification.
• Timing of biological events (e.g., flowering, migration) changes, affecting ecological relationships.
Impacts on Humans
• Threats to agriculture, water supply, and health (heat stress, vector-borne diseases).
• Coastal communities vulnerable to sea level rise and storm surges.
• Increased wildfires and air pollution.
Global Inequality
• Developing nations are most vulnerable, with fewer resources to adapt.
• Climate refugees may increase due to drought, sea level rise, or crop failure.
9.6 Ocean Warming
Causes
• Increased greenhouse gas emissions trap more heat in the atmosphere, which transfers to oceans.
Consequences
• Coral bleaching: stressed corals expel symbiotic algae (zooxanthellae), turning white and often dying.
• Disrupted migration and reproduction of fish and marine mammals.
• Decline in phytoplankton productivity in warmer surface waters → affects the entire food web.
• Ocean currents may weaken or shift (e.g., Gulf Stream), affecting climate patterns.
9.7 Ocean Acidification
Chemistry
• Oceans absorb CO₂ → forms carbonic acid → lowers pH.
• Carbonic acid dissociates into bicarbonate and hydrogen ions, reducing carbonate availability.
Effects
• Hinders shell formation in corals, mollusks, and some plankton (need carbonate ions).
• Weakens coral reef structures and disrupts reef ecosystems.
• Affects sensory abilities and behavior of fish species.
9.8 Invasive Species
Definition
• Non-native species introduced to new ecosystems, often lacking natural predators or controls.
Causes
• Global trade, travel, pet release, ballast water discharge, intentional introduction (e.g., pest control).
Examples
• Kudzu vine (U.S. Southeast), zebra mussels (Great Lakes), cane toads (Australia), Burmese pythons (Florida).
Impacts
• Outcompete or prey on native species, reduce biodiversity.
• Alter habitats, disrupt food webs, and damage infrastructure.
Control
• Physical removal, introduction of predators, public education, import regulation.
9.9 Endangered Species
Causes of Endangerment
• Habitat loss and fragmentation
• Invasive species
• Pollution (pesticides, heavy metals, plastics)
• Climate change and overharvesting (hunting, fishing, trade)
Characteristics of Vulnerable Species
• Specialist diet or habitat
• Small population size or restricted range
• Low reproductive rate or migratory behavior
Protection Efforts
• Endangered Species Act (U.S.)
• CITES (international treaty to prevent trade in endangered species)
• Habitat restoration, captive breeding, wildlife corridors
9.10 Human Impacts on Biodiversity
HIPPCO Acronym
• Habitat destruction
• Invasive species
• Population growth (human)
• Pollution
• Climate change
• Overexploitation
Conservation Strategies
• Preserve habitats and biodiversity hotspots
• Promote sustainable development
• Regulate hunting, fishing, and trade
• Engage communities in conservation and education
In a Nutshell
Global change encompasses a wide range of environmental disruptions driven by human activities, including ozone depletion, climate change, ocean warming and acidification, invasive species, and biodiversity loss. These changes threaten ecosystems, species, and human well-being. International cooperation, conservation strategies, sustainable practices, and public awareness are essential for mitigating impacts and ensuring a more resilient and biodiverse planet.