9.1 Stratospheric Ozone Depletion

Stratospheric Ozone and Life on Earth

• Ozone in the stratosphere absorbs UV-C and much of UV-B radiation

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

  • Human health benefits of stratospheric ozone:

    • Prevention of skin cancer & cataracts

    • UV-B & C mutate DNA (skin cancer) & cause oxidative stress in eyes (cataracts)

• Remember: tropospheric = respi. Irritant, damaging to plant tissue & precursor to photochemical smog

How Ozone Absorbs UV-B and UV-C

• UV-C breaks O2 into two free oxygen atoms (2 O)

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

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

• Continued formation & break down of O3 in stratosphere absorbs all UV-C & much UV-B radiation (protecting org. on earth)

Anthropogenic Ozone Depletion

• CFCs (chlorofluorocarbons) 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 of the 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 atm. for 50-100 years and can destroy up to 100,000 ozone molecules

Natural Ozone Depletion

• Antarctica spring melt forms polar stratospheric clouds (PSC)

  • Clouds made of water & nitric acid (HNO3) that can only form in consistent -1000 F temp. range found above Antarctica

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

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

9.2 Reducing Ozone Depletion

Reducing Ozone Depletion

• Main way to reduce anthropogenic O3 depletion is phasing out & replacing CFCs

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

    • Replaced with HCFCs (CFCs with hydrogen added)

    • HCFCs still deplete O3 and act as GHGs, 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 HCFCs is HFCs (still GHGs, but not O3 depleting since they don’t contain Cl)

      • **Replacements for HFCs are HFOs (just HFCs with C-C double bonds that shorten atm. 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

• Gases in earth’s atmosphere trap heat from the sun and radiate it back down to earth

  • Without 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

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

  • Portion coming back to earth is the “greenhouse effect”

Greenhouse Gases and Sources

• Most important Greenhouse Gases are:

  • CO2: FF comb, 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)

• measure of how much a given molecule of gas can contribute to the warming of the atmosphere over a 100 year period, relative to CO2

  • Based on 2 factors:

    • Residence time: how long molecule stays in the atmosphere

    • Infrared absorption: how well the gas absorbs and radiates Infrared radiation (IR)

  • CO2 has a GWP of 1 (all other gases are measured in relation to CO2)

  • Methane (CH4) remains in atm. around 12 yrs, absorbs more IR than CO2

  • N2O remains in atm. around 115 yrs, absorbs much more IR than CO2

  • CFCs remain in atm 50-500 yrs, absorb much, much, much more IR than CO2

9.4 Increase in Greenhouse Gases

Why Sea Level is Rising

• 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

• Melting Polar and Glacial Ice

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

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

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 = higher insurance and repair costs, lost property

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

  • Refugees forced to move inland

Disease Vectors

• Vectors

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

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

• Expanded Range

  • 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 pops. 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

  • Leads 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 diff. temp. tolerance

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

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

• 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 + thermal expansion

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

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 arctic warms faster than other areas of earth, temp. difference between equator & poles weakens

  • Because temperature & pressure diff. between polar & subtropical regions is what drives the polar jet stream, less diff. 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 have declined, or migrated 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

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

  • 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 gases

  • Oceans absorb much of earth’s heat due to high specific heat of water (est. 90% of earth’s warming from 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 respiratory stress or suffocation

  • 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 warmer waters & warm 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 coran and photosynthetic algae called zooxanthellae; algae supply sugar and 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

Ocean Acidification

• Increased CO2 in atmosphere → 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

Calcium Carbonate and Marine Organisms

• Marine organisms that make shells use calcium (Ca^+) and carbonate (CO3²-1) ions to build their calcium carbonate shells (calcification)

  • CO2 increase & ocean acidification makes carbonate ions less available

    • Carbonic acid ➡ increased H+ ions which bond w/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; weaker shells of coral, mollusks, and urchins

Climate Change and Ocean Acidification

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

  • CO2 increase directly correlated with ocean acidification

    • Inverse relationship b/w 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 the US $120 billion/year (2005 est.)

  • Lost agricultural 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 Engdangered

• 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

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

• 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

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

Protecting Endangered Species

• Poaching Prevention

  • Hiring 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 that gives 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

Endangerment by Taxon

• Amphibians: 41%

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

• Mammals: 25%

• Birds: 13%

• Warm Water Coral: 33%

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

• Conifers: 34%

  • Threatened by disease and warming temperatures expanding insect pest ranges

  • coniferous forests sequester 3x as much CO2 as temperate or topical forests

Specialists vs. Generalists

• Specialists

  • most 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

  • least likely to be endangered or become extinct

    • More likely to move to new habitat

    • More likely to adapt to new conditions

    • Advantaged by rapidly changing habitat conditions

Competition and Endangerment

• Shenandoah Salamanderer:

  • Endangered species, limited to ranges on only three specific mountains due to fiercely territorial red-backed salamander

• Red-backed Salamander:

  • Classified as “least concern” by IUCN. Guards rock habitats form 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 Human 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

• Over Exploitation

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

Habitat Fragmentation

• Breaking of larger, continuous habitats into smaller, isolated patches; disrupts breeding, hunting, migration

  • Roads and Pipelines

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

  • Agricultural and 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, Xantus Leaf-toed Gecko) that thrive in edge biomes

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

Climate Change

• Temperature Change

  • 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

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

Biodiversity and 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 the local climate

    • Many breeds are now extinct or at risk due to selection for only the highest productivity

Mitigating Biodiversity Loss

• Protecting and 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