Khan Academy + FiveAble APES U9 Notes

9.1: Stratospheric Ozone

• Ozone forms naturally in stratosphere (3 oxygen atoms)

  • Stratospheric ozone layer protects organisms and ecosystems by blocking harmful UV radiation

  • Naturally forms when UV radiation splits O2 into O atoms that collide and bond with other O2 molecules to form O3

• Stratospheric ozone depletion

  • When pollutants break down ozone molecules caused by human emissions of ozone depleting substances (CFCs, HBFCs, Halons, nitrous oxide)

    • Can also be broken down by natural phenomena like volcanic eruptions but human’s actions are more harmful

  • Thinner ozone layer = more UV radiation = more harmful impacts like skin cancer, cataracts, reduced phytoplankton abundance, lower plant productivity

  • Ozone thinning is SEASONAL:

    • Severe in polar regions due to polar stratospheric clouds that accumulate ozone depleting substances

    • Spring in each hemisphere — ozone depleted air moves to lower latitudes and warmer temperatures speed up chemical reactions that help ozone layers recover

  

• Ozone in troposphere (earth’s lower atmosphere) is harmful as it irritates respiratory systems and worsens health conditions, while reducing plants abilities to photosynthesis → lowered crop yields

  • Tropospheric ozone formed by VOCs, NOx, and sunlight

• Ozone depleting substances include:

  • Chlorofluorocarbons (CFCs) — chemicals that were used mainly in refrigerants, aerosols, and cleaning solvents

    • hydrobromofluorocarbons (HBFCs), halons, methyl bromide, hydrogen chloride

  • Nitrous oxide — released through human activities and natural phenomena

9.2 — Reducing Ozone Depletion

• Human emissions of ODSs led to substantial stratospheric ozone depletion

• Replacing ODSs (Ozone depleting substances) supports natural regeneration of ozone layer

  • Some substitutes work well but others have drawbacks

    • HCFCs can still damage ozone layers

    • HFCs (hydrofluorocarbons) and PFCs don’t break down ozone but are greenhouse gases that contribute to global warming

  • Other technologies and strategies can also reduce ozone depletion like using pumps instead of aerosol sprays

• Montreal Protocol — global treaty signed that aims to phase out ODs

• U.S. Clean Air Act — allows the environmental protection agency to regulate ODs with strict penalties for non-compliance

• Global efforts led to a 99% reduction of ODS emissions, causing increase in stratospheric ozone but full recovery is not expected until 2050

9.3 — The Greenhouse Effect

• Principal greenhouse gases include carbon dioxide, methane, water vapor, nitrous oxide, and chlorofluorocarbons (CFCs)

• Water vapor is a greenhouse gas but it isn’t that significant since it has a short residence time in the atmosphere

• Greenhouse effect — process by which energy from the sun is trapped in the form of heat by various types of gases

  • Results in the surface temperature necessary for life on earth to exist

  • Sun releases thermal and light energy → visible light and UV radiation reaches the earth → some energy absorbed by earth and then re-emitted as lower-energy infrared radiation → energy moves away from earth back into space

    • When infrared radiation sent back to earth’s surface reaches the atmosphere, greenhouse gases trap a portion of the radiation that causes the earth to rise in temperature, holding the energy into the troposphere

• Carbon dioxide (has a global warming potential — GWP — of 1) is used as a reference point for the comparison of different greenhouse gases and their impacts on global climate change

  • Chlorofluorocarbons have highest GWP, followed by nitrous oxide, then methane

• Thermal retention property — gases holding ponto heat at a greater rate than others

  • Greenhouse gases have higher thermal retention properties:

    • Carbon dioxide

    • Methane

    • Water vapor

    • Nitrous oxide

    • CFCs

9.4 — Increases in the Greenhouse Gases

• Rising sea levels and flooding

  • Melting of polar ice caps, ice sheets, permafrost, and glaciers, shoreline erosion

  • Temperature of earth’s ocean increases → water expands

• Spread of disease vectors

  • Diseases previously confined to the tropics spread to the poles: temperatures increase → disease vectors like mosquitos and ticks can survive and reproduce in areas they previously couldn’t

  • Warmer temperatures → ranges of host species can shift, bringing them in contact with new populations and allowing for more disease transmission

  • Warmer temperatures → changes in distribution and abundance of certain species, disrupting balance of ecosystems and increasing risks of disease outbreaks due to population density impacts

• Ocean acidification:

  • Increased CO2 from burning of fossil fuels → absorbed in oceans → increases concentration of dissolved CO2 → decreases pH of the ocean, making it more acidic

    • Reduces access to calcium, impacting the ability of some marine organisms to build and maintain their shells and skeletons

• Extreme weather events and changing weather patterns

  • Increased global temperatures → changes in atmospheric and ocean circulation patterns → affects occurrence of extreme weather events

• Loss of biodiversity

  • Changes the range of species, leading to species displacement as a pursuit of finding more suitable habits

    • If suitable habits are not available or if they can’t migrate/evolve quickly enough, they can become extinct

  • Impacts the availability of water, severity of natural disasters, spread of diseases

9.5 — Global Climate Change

• Heating and cooling climate cycles

  • Earth naturally warms and cools over thousands of years

  • Scientists study ice cores (in antarctica) to track past CO2 levels

    • Air bubbles in ice = “time capsules” of ancient atmosphere

    • Higher CO2 in bubbles = warmer climate in that area

  • Earth moves heat from the equator to the poles using air currents and ocean currents that help keep the climate stable

    • Climate change disrupts these currents leading to stronger storms, hotter weather, colder weather, more unpredictable weather

• Positive feedback loops at the poles:

  • Melting ice and snow → less solar radiation reflected and more solar radiation absorbed → poles warming even faster = POSITIVE FEEDBACK LOOP FOR WARMING

  • Positive feedback loops causes

    • Rising sea levels

    • Loss of habitat (polar bears, seals, etc.)

    • Thawing permafrost → methane released → more warming

• Rising sea + marine impacts

  • Melting ice → more volume to oceans → flooding in coastal cities

  • Sea levels make species gain habitat (flooded shelves) and others lose habitat (sunlight no longer reaches deeper water = no photosynthesis)

9.6 — Ocean Warming

• Climate change in the oceans

  • Ectotherms (fish, amphibians, reptiles, invertebrates) depend on external sources of heat for body temperature: meaning that body temperature of an aquatic ectotherm is very close to temp of surrounding water

    • Warmer ocean waters → organisms facing metabolic stress and can lose ability to metabolize their food/reproduce

• Impacts on coral:

  • Coral has symbiotic relationship with algae (zooxanthellae): algae have stable habitat and nutrients → provides coral with sugar

    • Algae in coral are sensitive to temperature and cannot live in warmer water → when algae die and are expelled, coral turns white/bleaches → cannot recover

• Melting of sea ice → destroys polar habitats and changes habitats globally with sea-level rise and changes to currents

9.7 — Ocean Acidification

• Acid formation ^^

• Ocean acidification: caused by absorption of excess atmospheric CO2 into the ocean, lowering pH levels

  • Due to 200 years of global industrialization, ocean pH levels have dropped by 0.1 pH units (30% increase in ocean acidity levels)

• Calcium Carbonate

  • CO2 + sea water → carbonic acid → reduction of pH in water → reduces available calcium carbonate in the ocean (needed to help build skeleton/shells of marine organisms)

  • Calcium carbonate used to control internal pH and reglate the number of calcium ions in their bodies

• Fish physiology (behavior + physiology) is disrupted through acidification, making it difficult for them to interact with stimuli in their external environment

• Aquatic plants thrive in a CO2 rich environment, so an excess of CO2 can create eutrophication heavy environment

• Pteropods — small pelagic snails that make up the basis for the food chain for a wide variety of animals

  • Current predicated acidity levels would dissolve their shells and lead to the collapse of their species, creating a domino effect on the rest of the organisms that rely on it

9.8 — Invasive Species

• Invasive species: Species that can live, and thrive, outside of their normal habitats

  • Can sometimes be beneficial but are considered invasive when they threaten native species

  • Often generalists, r-selected species, and therefore may outcompete native species for resources

  • Can be controlled through a variety of human interventions

    • Physical removal: manually removing individuals/entire populations of invasive species

      • hand-pulling, cutting, digging, and trapping

    • Chemical control: pesticides and other chemicals killing/inhibiting the growth of invasive species

    • Biological control: using natural predators, pathogens, or competitors of the invasive species to reduce its population

    • Habit modification: altering environment to make it less suitable for invasive species and more suitable for native species

    • Monitoring and early detection: regularly monitoring new invasive species and taking action as soon as they are detected

    • Public education/outreach: educating public about negative impacts of invasive species and encouraging them to take action to prevent the spread of the species

  • Prevention: most effective and cost-efficient strategy for controlling invasive species (strict quarantine regulations, inspections of cargo/vehicles, and regulations on import/trade of live organisms)

9.9 — Endangered Species

• Endemic species — species that exist in a specific area and nowhere else in the world

  • Have limited range, high habitat, or resource specificity, and low abundance

• Classification: any organism can become endangered and are classified by the International Union for Conservation of Nature (IUCN) into the following categories:

  • Extinct (EX) — These species no longer exist and have become extinct

  • Extinct in the wild (EW) — survives only in captivity, cultivation, and/or outside the native range, as presumed after exhaustive surveys

  • Critically endangered (CR) — these species are at an extremely high risk of extinction in the wild and their population is declining at an alarming rate

  • Endangered (EN) — species at a very high risk of extinction in the wild and their population is declining rapidly

  • Vulnerable (VU) — meets one of the 5 red list criteria and thus considered to be at high risk of unnatural (human-caused) extinction without further human intervention

  • Near threatened (NT) — species at risk of becoming endangered in the near future

  • Least concern (LC) — these species are considered to have a low risk of extinction and are not considered endnagered

• IUCN’s 5 criteria to classify organisms and assess conservation status:

  • Reduction in population (decreased significantly)

  • Geographic range (restricted)

  • Population size (less than 2500 mature individuals)

  • Extremely small population size (less than 250 mature individuals)

  • Probability of extinction (analysis that shows the species becoming extinct in the wild at least 20% within 20 years or 5 generations)

• Risk Factors:

  • How fast species reproduce

    • R-species: reproduces quickly → most babies don’t survive but the species bounces back fast → less risk of extinction

    • K-species: reproduces slowly → babies more likely to survive but takes longer to recover if numbers drop → more risk of extinction

  • How well species adapt to change

    • Specialists: live in a small range of tolerance → don’t adapt well to change → high extinction risk

    • Generalists: wide range of tolerance → adapts to change better → lower extinction risks

• Overharvesting: when individuals are removed from a population at a rate faster than the population can replace them → leads to population declines and extinction

  • Regulations like hunting/fishing restrictions can help overharvesting but in some areas, regulations are not strongly enforced, leading to illegal poaching

• Plant/animal trade: represents a serious threat to the persistence of some species

  • Lacey Act and Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES): developed to control and regulate the trade of threatened and endangered plants and animals

• Endangered species act: federal law in the US that aims to protect and recover species in danger of extinction throughout all or a significant portion of their range

  • Administered by the US Fish and Wildlife Service and the National Oceanic and Atmospheric Administration (NOAA) → one of the strongest laws in the world for protecting endangered and threatened species

  • Designation of “critical habitat” - species areas that are essential for the conservation of the species, as well as the prohibition of harming the listed species and their trade, including their fur or body parts

  • Can restrict certain human activities in areas where listed species live, including how landowners use their land, but had significant success in protecting and recovering endangered and threatened species

• Breeding programs + other organizations:

  • Institutions (zoos, aquariums, NGOs, research institutions) can serve as education centers while also using animals in breeding programs to rebuild populations of critically endangered species

9.10 — Human Impacts on Biodiversity

• Human population growth → more land needed for housing, agriculture, industry → destructions of natural habitats and displacement of native species

  • Leads to pollution, overconsumption of resources, and introduction of invasive species, climate change, overfishing, pollution also contribute to loss of biodiversity

• HIPPCO (Habitat destruction, Invasive species, Population growth, Pollution, Climate change, and over Exploitation) — major factors causing a decrease in biodiversity

  • Habitat destruction: Destruction, fragmentation, or degradation of natural habitats, making it difficult for species to live

    • Caused by urban development, agriculture, and logging

    • Leads to soil erosion, loss of biodiversity, and destruction of indigenous peoples’ ways of life

  • Invasive species: non-native species that are introduced and are causing harm to native species

    • Outcompetes native species for resources and spreads diseases

    • Disrupts the ecological balance of the region

  • Population growth: increased in human activities that harm wildlife and their habitats, such as urbanization and resource extraction

    • Destruction of natural habitats, habitat fragmentation, overuse of resources

  • Pollution: release of chemicals, plastic debris, and other harmful pollutants

    • Impacts different organisms, tourisms, recreation, other activities

    • Impacts human health

  • Climate change: changes in temperature, precipitation, and other weather patterns that can make it difficult for species to survive

    • Affects migration patterns, reproduction, and other aspects of animal behavior

  • Overexploitation: overuse of natural resources, including the overharvesting of wild animals and plants

    • Leads to population declines + endangerments

• Conservation: protecting/managing genetic diversity within species

  • Preserving habitats, protecting/managing genetic diversity, promoting sustainable use of natural resources, addressing impacts of climate change

• In-situ conservation — restoring habitats and establishing protected areas

• Ex-situ conservation — protective custody and captive breeding