15-20% of the AP Exam

Topics

9.1 Stratospheric Ozone Depletion

9.2 Reducing Ozone Depletion

9.3 The Greenhouse Effect

9.4 Increases in the Greenhouse Gases

9.5 Global Climate Change

9.6 Ocean Warming

9.7 Ocean Acidification

9.8 Invasive Species

9.9 Endangered Species

9.10 Human Impact

These notes are based on Mr Jordan Dischinger-Smedes’s YouTube videos and the fill in template notes for these videos created by Carolyn Kelleher Mendonca. Some changes were made. Videos available here.

Good luck on the AP Test! 🩷

9.1-9.2 Stratospheric Ozone Depletion & Reducing Ozone Depletion

Stratospheric Ozone & Life on Earth

Ozone in the stratosphere absorbs UV-C and much of UV-B radiation, which are harmful.

• Without ozone layer, life on land would not be possible since UV-B & C radiation cause significant tissue damage and mutates DNA,

• Human health benefits of stratospheric ozone:

  • Prevents skin cancer and cataracts

  • UV-B and C mutation DNA and cause oxidative stress in eyes

Remember: Tropospheric Ozone is a respiratory irritant, damaging to plant tissue & precursor to photochemical smog

How Ozone Absorbs UV-B & UV-C

UV-C breaks O2 into free O2

• When a free oxygen atom from this reaction binds with an oxygen O2 molecule, ozone (O3) is formed

• UV-C also reverses the run by breaking O3 into O and O2, which can then bond with another free O to form O2

• Continued formation & breakdown of O3 in the stratosphere absorbs all UV-C & much UV-B radiation (protecting organisms on earth)

Anthropogenic Ozone Depletion

CFCs are a primary anthropogenic (human) cause of O3 breakdown

• Used as refrigerant chemicals and propellants in aerosol containers (hair spray, febreeze, etc.)

• UV radiation causes free chlorine atom to separate from CFCs

• Highly electroneg. chlorine atom bonds to One oxygen atoms of ozone (O3) converting it into oxygen (O2)

• Free O atom then bonds to O from chlorine monoxide to form O2 and free Cl atom to go break down more O3

  • One single Cl atom persists in the atmosphere for 50-100 years and can destroy 100,000 O3 molecules

Natural Ozone Depletion

Antarctica spring melt forms polar stratospheric clouds (PSC)

• Clouds made of water and nitric acids (HNO3) that can only form in consistent -100 F temp. range found above antarctica

• In presence of PSCs, chlorine nitrate (ClONO2) and hydrochloric acid (HCl) react & give off Cl2

  • Cl2 (broken by sun) into 2 free Cl atoms

Remember what Cl atoms due to ozone from CFCs (break down O3)

9.2 - Reducing Ozone Depletion

The main way to reduce anthropogenic O3 depletion is phasing out and replacing CFCs.

• Montreal Protocol (87’) was a global agreement to phase out CFCs in refrigerators, aerosols and other uses

• Replaced with HCFCs (CFCs with hydrogen added)

• HCFCs still delete O3 and act as GHG, but to a lesser degree than CFCs

• Not a permanent solution, but a temporary transition option (phase out in dev. Nations after 2020, developing nations have until 2030)

**Replacement for HCFC is HFC (still GHG, but does not deplete O3 since they don’t contain Cl)

**Replacements for HFCs are HFOs (just HFCs with C-C double bonds that shorten atmosphere lifetime & GWP)

9.3 The Greenhouse Effect

Solar Radiation

Not all incoming solar radiation reaches earth’s surface

• 26% reflected back into space by clouds & atm.

• 19% absorbed by atm. & clouds & radiated

• out into space & down to earth

• The rest reaches earth’s surface where it can be absorbed or reflected (depending on the albedo of the surface it strikes)

  • Darker, lower albedo surfaces absorb sunlight & release infrared radiation (which we feel as warmth)

  • Lighter, higher albedo surfaces reflect sunlight, directly back out into space, or into clouds/GHGs that absorb it

The Greenhouse Effect

Gasses in earth’s atmosphere trap heat from the sun & radiate it back down to earth. Without the greenhouse effect, earth would be too cold to support life.

How it works:

• Solar radiation (light waves like UV & visible light) strike earth’s surface, heating it

• Earth’s surface releases infrared radiation (heat)

• Greenhouse gasses absorb infrared radiation & radiate it both out into space and back toward earth

• The portion of infrared radiation (heat) coming back to earth is the “greenhouse effect”

Greenhouse Gasses & Sources

Most important Greenhouse Gases (GHGs) are:

• CO2 - FF combustion, decomposition, deforestation

• Methane (CH4) - natural gas extraction & combustion, animal agriculture, anaerobic decomp. (especially permafrost thaw)

• Nitrous oxide (N2O) - agricultural soils (denitrification of nitrate, especially in overwatered, over fertilized soils)

• CFCs/HCFCs/HFCs - refrigerants, blowing agents in aerosol products

*Water vapor (H2O) - evaporation & transpiration from plants

*Technically a GHG by definition, but doesn’t drive atm. temp change (other way around - temp. Controls atm. H2O vapor level)

Global Warming Potential (GWP)

Based on 2 factors:

1) Residence time: how long molecule stays in the atmosphere

2) Infrared absorption: how well the gas absorbs & radiates Infrared radiation (IR) CO has a GWP of 1 (all other gasses are measured in relation to CO )

• Methane (CH4) remains in atmosphere around 12 yrs, absorbs more IR than CO2, and GWP = 23-84

• N2O remains in atmosphere around 115 yrs, absorbs much more IR than CO2, and GWP = 300

• CFCs remain in atmosphere 50-500 yrs, absorb much, much, much more IR than CO2, and GWP = 1600-13000

9.4 Increase in Greenhouse Gasses

Thermal Expansion

• Water molecules move slightly further apart when they’re heated

• All the water molecules of ocean moving slightly apart leads to sea level rising

• This water flows into the ocean and leads to sea level rise

• Melting Polar & Glacial Ice

  • Increased greenhouse gasses lead to a warmer climate & more melting of ice sheets (at the poles and glaciers)

Environmental Impacts of Sea Level Rise

🏔 Flooding of coastal ecosystems like estuaries (mangroves, salt marshes)

• Loss of species that depend on arctic and tundra ecosystems (polar bears, penguins, reindeer)

• Loss of thaw-freeze cycle that glaciers go through, depriving surrounding ecosystems and human communities of water source

Human Impacts

🏔 Relocation of coastal human populations

• Increase in flood frequency causes higher insurance and repair costs, lost property

• Saltwater intrusion (salt water pushing into ground water & contaminating wells)

• Refugees forced to move inland

Disease Vectors

Expanded Range

• Living organisms (usually mosquitoes, ticks, fleas) that can transmit diseases from human to human or animal to human

Vectors

• Ex: malaria, Zika, West Nile, dengue fever, cholera

• Warmer temperatures allow insect-transmitted diseases to spread to parts of the world previously too cold

• As the insect vectors expand their range further from equators, toward poles, new human populations are at risk

9.5 Global Climate Change

Historic Climate Change

⛰ Earth’s climate has varied over geologic time, largely due to variations in earth’s orbit around the sun

• Varies in obliquity (~40,000 yrs.) exposing northern latitudes to higher insolation at different times

• Varies in eccentricity (~100,000 yrs.) bringing it closer to and further from the sun at different times

  • More eccentric = further from sun

Changes in eccentricity led to predictable variation in Earth’s climate called Milankovitch Cycles

Earth’s Historical Climate

Scientists have measured and estimated earth’s historical temperature and CO2 levels using 3 main pieces of evidence

• Foraminifera shells in ocean sediments - different species have different temperature tolerance, so viewing the species present at a certain time can show what the temperature was.

• Air bubbles in ice cores that contain ancient atmospheric gas (CO2 levels)

• ¹⁶O vs. ¹⁸O isotope concentrations in ancient ice ( ⬆ ¹⁸O = ⬆ temperature)

Global ice ages, followed by warmer periods occur roughly every 100,000 years CO2 levels are strongly correlated with temperature, but causality isn’t fully understood

Effects of Climate Change

Rising Temperature - habitat/species loss, drought, soil desiccation, heat waves, increased precipitation in some regions

Rising Sea Level - due to glacial (polar) ice melt and thermal expansion

Melting of Permafrost - permanently frozen tundra soils that begin to thaw & release methane & CO2 from anaerobic decomposition, causing a positive feedback loop.

Impact on Coastal Communities

Property loss, damage, potential relocation:

• Coastal communities, especially poorer ones that can’t build up may need to relocate inland

• Seawalls or other barriers can be built higher, but this just delays eventual flooding

Loss of barrier islands: islands that buffer coastal communities/ecosystems from wind & waves may be lost as sea level rises

Impact on Atmospheric Currents

Widening & weakening of hadley cell: as temp. diff. between equator and poles decreases, air ascending and expanding from equator travels further before sinking

• This shifts subtropical zones (dry, desert biomes) toward the poles and expands the tropics

• Regions between 300 and 60o may experience drier climate as cool, dry, descending air from hadley cell shifts north & south

Weakened, destabilized Jet Stream

• As the arctic warms faster than other areas of earth, temperature differences between equator & poles decreases

• Because temperature & pressure different between polar & subtropical regions is what drives the polar jet stream, less different between them means weaker, wobblier jet stream

• Leads to extreme cold spells in eastern US & dry spells in western US

Impact on Marine Ecosystems

Altered range of marine ecosystems: some new marine habitats will be formed by rising sea level flooding coastline

• Some areas of ocean will become too deep to receive sunlight & photic zone will shift up, further from ocean floor

• Altered ranges for organisms: warm water holds less O2, so many fish populations decline or migrate to cooler waters

Impact on Ocean Circulation

Suppression of thermohaline circulation: global ocean current that redistributes heat from the equator, salt, and nutrients by mixing ocean waters could slow or stop altogether

• Ice melt from Greenland ➡ especially cold, fresh water buildup in north atlantic

• Freshwater is less dense than salt, preventing it from sinking

• This cold north atlantic slows warmer Gulf Stream waters, cooling Europe & slowing global thermohaline circulation

Unequal Global Warming

Polar regions of earth are warming faster than other regions (polar amplification)

• Especially the arctic (N pole) because there is more land & less water to absorb heat

• Melting sea ice = more exposed ocean water, which absorbs more sunlight than ice & snow, leading to more ice melting (positive feedback loop)

• Distribution of tropical heat to poles by thermohaline circulation also warms poles

Unequal Global Warming

Melting of Permafrost - permanently frozen tundra soils that begin to thaw & release methane & CO2 from anaerobic decomposition

CH4

• Air pollution adds soot & other PM to atmosphere, distributed to poles by atmospheric circulation

• Darker, soot/PM covered ice absorbs even more heat due to lower albedo

Impact on Polar Ecosystems

Arctic sea ice loss = habitat loss

• Seals use it for resting and find holes for breathing

• Algae grow on ice, forming base of arctic food web

• Polar bears use ice for hunting seals at breathing holes

9.6 - Ocean Warming

Atmospheric Warming ⬅➡ Ocean Warming

As the atmosphere warms, heat is transferred to the ocean

• Ocean absorbs heat radiated back to earth by greenhouse gasses

• Oceans absorb much of earth’s heat due to high specific heat of water (est. 90% of earth’s warming from the past 50 yrs. occured in oceans)

• Thermohaline circ. distributes heat absorbed at surface to depths & other areas of earth

• Heat absorbed by ocean can transfer back to atmosphere for decades

Effects on Marine Species

🏔 Warmer water holds less O2; causing resp. stress or suffocation

• Migratory routes and mating seasons can be altered, especially for whales

  • Reproductive timing, often tied to temp. change, can be disrupted (fish esp.)

• Habitat loss: coral bleaching with heating ocean; shallow, sunny waters ideal for algae & coral become deeper from ice melt

• Toxic algae blooms: toxic blue-green algae prefer farmer waters & farm temperature prevents mixing of water, enabling algae blooms

• Blue-green algae release toxins into the water that can kill marine species

  • Can also block sunlight & lead to hypoxia

Coral Bleaching

🏔 Coral reef = mutualistic relationship between coral & photosynthetic algae called zooxanthellae; algae supply sugar & coral supply CO2 + detritus (nutrient containing org. matter.)

• Algae have narrow temp. tolerance and leave the reef when temp. rises

• Pollutants from runoff (sediment, pesticides, sunscreen) can also force algae from reef

• Coral lose color & become stressed and vulnerable to disease without algae (main food source)

9.7 - Ocean Acidification

Increased CO2 in atmosphere causes increased ocean CO2 (direct exchange)

• CO2 combines with ocean water to form carbonic acid (H2CO3)

• Carbonic acid dissociates into Bicarbonate ion (HCO3-) and H+ ion

Marine org. that make shells use calcium (Ca+) and carbonate (CO32-) ions to build their calcium carbonate shells (calcification)

• CO2 increase & ocean acidification makes carbonate ions less available

• Carbonic acid ➡ increased H+ ions which bond with carbonate to form Bicarbonate (HCO3-)

Marine shells breakdown as pH decreases and carbonate ions are less soluble in ocean water

Fewer carbonate ions = less calcification; 􏰀eaker shells of coral, mollusks, and urchins

Anthropogenic causes for ocean acidification: fossil fuel combustion (CO2), deforestation (CO2), and coal/gas combustion (NOx/SOx → acid precip.)

• CO2 increase directly correlated with ocean acidification

• Inverse relationship between atm. CO2 & ocean pH (low pH = more acidic)

Ocean pH has decreased from 8.2 to 8.1 in past 150 years; could decrease to 7.8 by 2100

*pH = log scale so 8.2 to 8.1 = 30% decrease

9.8 Invasive Species

Invasive Species Basics

Species not native to an area, introduced often by human transport

• No natural predators to control pop.

• Highly competitive (aggressive feeders or fast growers) for resources

• Can thrive in their non-native habitats

r-selected, generalists

R-selected and generalist species are more likely to be invasive

• High biotic potential & low parental care

• Highly adaptable

• Diverse habitat & food needs

Invasive Species To Know

Zebra Mussel

• Transported by ship ballast water

• Aggressive filter feeders, eating algae many other species rely on

• 1 mil. eggs/yr.

• Clog intake pipes

Kudzu Vine

• Planted to limit soil erosion in southern US

• Grows very rapidly

• Outcompetes natives for sunlight; growing over them

• No herbivore control in US

Asian Carp

• Brought in to control algae growth in aquatic farms

• Escaped to Mississippi river; outcompete native fish for food and space

• Decreases fishery production & value

Emerald Ash Borer

• Spread by wood packing materials of ships/planes & fire wood

• Larvae laid in bark, eat their way into phloem

• Disrupts tree nutrient transport, killing them

• Expanding range due to global warming

Cane Toad

• Introduced to eat cane beetles causing sugarcane crop loss in Australia

• Became invasive due to huge appetite

• Drove declines in other amphibians and small reptiles

Pythons (FL)

• Brought to Florida as pets, released into wild by owners

• Decimated mammal populations in Everglades ~90-95%

• Aggressive hunters with no natural predators

Controlling Invasives

🏔 Invasives estimated to cost US $120 billion/year (2005 est.)

• Lost agr. productivity, tourism, property value decline, fishery decline, control and removal costs

Control/Removal Methods

• Laws preventing transport of invasives (firewood for emerald ash borer) ○ Removal of hosts (dead ash trees for EAB) to reduce spread

• Careful boat cleaning & inspection (zebra mussels)

• Introduction of natural predator (biological control)

  • Chinese wasps to kill emerald ash borer

• Physical removal (hunting pythons, detaching z. mussels, pulling plants out, cutting trees down)

9.9 - Endangered Species

How Species Become Endangered

Poaching

• Poachers hunt exotic species for fur, tusks, horns

• May also be over harvested or hunted for food

• Removed from wild & sold as pets

• Special food/habitat needs

• Niche specialists are more prone to endangerment due to specific food/habitat needs

Invasives

• Invasives can outcompete natives for resources (food, water, sun, space)

• Zebra mussels have endangered 30 native mussel species in US rivers

Climate Change

• Shifts habitats of many species

• Migration to new habitat is harder with fragmentation/loss

• Less tolerant of changing climate, habitat loss, wildfires, deforestation, urbanization, etc.

• Changes in temp/precip. can occur too rapidly for some species to migrate or adapt

Protecting Endangered Species

Poaching Prevention

• Hiring of armed guards to monitor populations and prevent poaching

• Laws that punish poaching severely, with stiff fines or jail time

Legislation

⛰ CITES: International agreement for countries to set up agencies to monitor import and export of endangered species (as specified by IUCN Red List)

⛰ Endangered Species Act: US law giving USFWS power to designate species as endangered or threatened, monitor trade, and purchase land critical to these species’ habitats

Protect Wildlife Habitats

• Designating areas with important habitats as:

  • National parks

  • Wildlife preserves

  • Animal sanctuaries

• Prevention of hunting, development, fragmentation, deforestation

• Allows species to breed and reestablish population size

IUCN Red List

Endangerment by Taxon

Amphibians -

• Especially vulnerable to climate change due to biphasic life (relying on water and land) and highly permeable skin

Warm Water Coral -

• Threatened by changing ocean temperature and pH (ocean acidification from increasing atm. CO2 levels)

Conifers -

• Threatened by disease and warming temperatures expanding insect pest ranges

• Coniferous forests sequester 3X as much CO2 as temperate or tropical forests

Specialists vs. Generalists

Specialists

More likely to be endangered or become extinct

• Less likely to move to new habitat

• Less likely to adapt to new conditions

• Disadvantaged by rapidly changing habitat conditions

Generalists

Less likely to become endangered or extinct

• Advantaged by rapidly changing habitat conditions

• More likely to move to new habitat

• More likely to adapt to new conditions

Competition & Endangerment

Shenandoah salamander: endangered species, limited to ranges on specific mountains due to fiercely territorial red-backed salamander

- VS

Red-backed Salamander: Classified as “least concern” by IUCN. Guards rock habitats from other salamander species, preventing range expansion

• Interspecific competition: competition for resources (food, nest sites, water)

• amongst members of different species

  • Can cause species to become threatened, especially when combined with general habitat fragmentation or loss due to human land use

  • Can further threaten species already vulnerable to habitat disruption due to climate change

9.10 - Humans Threats to Biodiversity

HIPPCO

Habitat Fragmentation/Loss

• Deforestation (lumber, cities, roads), wetland draining (ag, urbanization), river water level decreased by dams.

Invasive Species

• Invasives such as z. mussel and kudzu vine outcompete native species for food/space, lowering populations

Population Growth

• Human pop. growth drives hab. loss Urbanization, ag. expansion to feed more people remove/fragment hab.

Pollution (Pollutants)

• Oil spills reduce marine org. pop. sizes Pesticides (glyphosate, atrazine) kill non-target species

Climate Change

• Shifts biomes & therefore species habitat ranges, can change temp. & precip. patterns too rapidly for a species to adapt or migrate, causing pop. decline or extinction

Overexploitation

• Excessive hunting or poaching (faster than reproductive rate) leads to pop. decline & potential extinction

Roads & Pipelines

• Roads & oil/gas pipelines fragment habitats; disrupt movement & lead to fatal collisions with vehicles

Agricultural & Urban Land Use

• Clearing forest/grassland for ag. fields or urbanization fragments those habitats.

Logging

• Both removal of trees & construction of logging roads to transport lumber fragment forest ecosystems

Metapopulations

🏔 Some species are more disrupted by fragmentation than others

• Large predators needing large hunting space

• Smaller populations of large k-selected mammals may struggle to find mates

🏔 Habitat Fragmentation creates smaller, isolated subpopulations

• Smaller subpopulations have less genetic diversity, are more prone to inbreeding depression, and are less resilient to env. disturbance or disease

• Metapopulations are mostly isolated, subpopulations connected by habitat corridors; this can allow some gene flow (mating between populations) and improve genetic diversity

Edge Effect

“Edge habitat” where two ecosystems such as forest-grassland or ocean-river (estuaries) meet have diff. characteristics than the middle of each ecosystem

• Some species thrive in the edge habitat & biodiversity is often higher in edge habitats due to diversity of food, shelter, and nutrient resources

• Edge habitats can expand range of potentially disruptive species (ex: brown headed cowbird) that thrive in grassland-forest edge

• Brood parasite that leaves its eggs in the nests of songbirds for them to raise, unknowingly

Climate Change

Temperature change

• Climate change can shift the range of habitats, or increase/decrease their range altogether

• Warming temp. can shift biomes

• Boreal forest & temperate coniferous forests may shift northward; tundra may decrease

Precipitation change

• Warming global. temp. will decrease precipitation in some areas, leading to soil desiccation and desertification

• Will increase in some areas, expanding tropical ecosystems

Sea level rise

• Estuary habitats (salt marshes, mangroves) become fully submerged & more saline; coastal ecosystems become flooded

Biodiversity & Domestication

• Domestication of species for agriculture generally decreases genetic and species biodiversity Crops

• Fewer plant species are grown as selective breeding and GM results in only the highest yield species

• GM use and selective breeding also lead to less genetic diversity in crops, making them more vulnerable to disease or environmental disruptions

Livestock

• Historically, there have been over 8,000 breeds of the 11 species most commonly eaten by humans

• Breeds were uniquely adapted to local climate - Many breeds are now extinct, or at risk due to selection for only highest productivity

Mitigating Biodiversity Loss

Protecting & Connecting Habitats

• Protecting important habitats by creating national parks, nature preserves, or preventing them from being developed

• Connecting fragmented habitats with wildlife corridors enables movement/breeding

Sustainable Land Use

• Urban growth boundaries, infill, and building up (not out) to reduce urban sprawl can preserve existing habitats

• Expanding parks, urban gardens, green roofs can provide habitat for many species

• Sustainable agriculture, lowering meat consumption can reduce ag. land needs, preventing hab. loss

Restoring Lost Habitats

• Replanting clear-cut forests

• Reestablishing prairies on old ag. fields or golf courses