Unit 9: Global Change 

9.1 Stratospheric Ozone Depletion

Difference between “good” ozone and “bad” ozone?

• Good ozone in stratosphere that protects/absorbs from UV radiation 

• Bad ozone: Ground-level; photochemical oxidant (sunlight reacts with SO2 and NOs) in the troposphere

How does the Ozone layer form?

• Step 1: Oxygen molecule (O2)+ UV rays(UV-C) = atomic oxygen( 2 O) (2 single oxygen atoms)

• Step 2: atomic oxygen(O) + oxygen molecule (O2) = ozone (O3)

What are CFCs?

• Ozone is being depleted by CFCs (chlorofluorocarbons)

  • Organic, MAN-MADE, synthetic, nontoxic, nonflammable, very stable

    • Contain C, Cl, F

  • Primary pollutant: put directly into the atmosphere

  • Source of pollution: refrigerators, air conditioners, fire suppressants, aerosol sprays

• CFC can last in the atmosphere for up to 45 years

• Ozone layer in stratosphere is protector (absorbs UV rays)

• Sunlights breaks a Cl- atom from the CFC atom; chlorine atom encounters an ozone molecule; chlorine removes an oxygen atom from ozone (O3)=O2 & O+Cl; Free oxygen atom releases chlorine

• POSITIVE FEEDBACK LOOP

What is the hole in the ozone layer

• In the mid 80s it was noticed that there was thinning of the layer in Antarctica

• Happened b/c there are a lot more free ice molecules in the atmosphere that encourages chlorine process to occur

Increased UV on human health

• Cataracts: intense UV light on the eyes, causes cloudiness

• Skin cancer: melanocytes produce melanin to protect the skin from UV rays; if UV rays exceed what can be blocked by your level of melanin, sunburn results

9.2 Reducing Ozone Depletion

What important international agreement limited/banned CFCs in many countries?

• Replacing CFCs with HFCs (hydrofluorocarbons); still a greenhouse gas but doesn't do same damage

• Montreal protocol of 1987: lot of nations came together and agreed to ban/reduce CFCs emitted into the atmosphere (EFFECTIVE!)

9.3 The Greenhouse Effect

• Greenhouse gases let the sun’s short wave radiation (visible light) reach the earth, but trap some of the long wave (infrared or heat) radiation coming from the warm earth

  • 1. Incoming solar radiation = UV and visible light

  • 2. 1/3 reflected back into space

  • 3. Remaining lights is absorbed by clouds and planets surface (these become warmer and emit infrared radiation)

  • 4. Radiation is either absorbed by the GHGs or emitted into space

  • 5. More greenhouse gases= more IR absorbed and emitted back to earth

• The process should be in equilibrium (short term, inputs might be higher or lower, which causes global warming/cooling; ice ages)

Greenhouse gases in the atmosphere

• N2 and 2 = 99% of greenhouse gases - NOT GHGs

• Greenhouse gases responsible for trapping heat in the atmosphere

  • Major greenhouse gases: 

    • Water vapor (H2O): short residence time so does not contribute much; absorbs more IR than anything but does not persist)

    • Carbon Dioxide (CO2): used as a reference point for climate change

    • Methane (CH4): very strong GHG; 

    • Ozone (O3)

    • Nitrous Oxide (N2O)

    • CFCS (not natural)

• Global warming potential: how much a molecule can contribute to global warming over 100 years relative to a molecule of CO2 (how well it absorbs IR, how long it persists)

  • Potential + concentration = total effect

• Natural sources of GHGs: 

  • Volcanoes- ash reflects incoming radiation, so cooling effect

  • decomposition/digestion- dead organic matter converted into CO2 unless there is not enough O2 (not enough O2> its converted to CH4)

  • Methane from wetlands; termites

  • Denitrification- N2O (nitrous oxide) (nitrate NO3> nitrite NO2> nitric oxide NO> nitrous oxide N2O> nitrogen gas N2)

  • Evaporation and evapotranspiration- water vapor

9.4 Increases in Greenhouse Gases

Anthropogenic sources of GHGs

1. Fossil fuels- CO2, methane, N2O (PM lowers albedo that does not reflect sunlight/absorbs heat, black soot)

2. Agriculture- overirrigation= low O2, so methane; fertilizers= denitrification; livestock= cattle and sheep methane

3. Deforestation- less photosynthesis, more CO2, burning releases PM, methane, N2O

4. Landfills- methane (food scraps/garden waste create acids in anaerobic conditions and pollute groundwater; leachate soaks into surrounding ground and contaminated groundwater; methane produced from food waste kept in anaerobic conditions)

5. Modern chemicals like CFCs (HCFCs do not create as big of problem)

Human sources of methane

1. Fossil fuel production, distribution

2. Livestock farming

3. Landfills and waste all 3 = 80%

4. Biomass burning

5. Rice agriculture

6. Biofuels

Nitrous Oxide

1. fertilizers/agricultural soil

2. Fossil fuels are majority

Carbon dioxide

1. Fossil fuel combustion = 95%

   1. Transportation 42%

   2. Industrial 23%

   3. Electricity generation(in state) 14%

   4. Electricity generation (imports) 10%

   5. Residential 6%

9.5 Global Climate Change

• Global Change: Planetary-scale changes in Earth Systems (land, air, life, soil, atmosphere, oceans, humans)

• Global Climate Change: Changes in temp., precipitation, wind, storms, currents, etc

• Global warming: Increase in average temp over earth over time

• IPCC: intergovernmental Panel on climate change (1988) created by UN with 3,000 scientists worldwide

Increasing CO2 concentrations

• Keeling Curve (began in 1959)

  • First to accurately measure CO2

  • CO2 levels vary seasonally and increase overall

• Seasonal fluctuation: vegetation; most of it in N hemisphere so overall there is a huge decrease in spring/summer

• Latitudinal difference: 90% of world pop in N hemisphere; 67% of world land

  • Phytoplankton produce >40% of world’s oxygen

• Increases overall because of: increased emissions from fossil fuel combustion; net destruction of vegetation

Temperature Increases

• Global temperatures have increased on average 1.4 F

• 45% of the northern ice caps have melted

Changing Species Compositions

Proxy Data: preserved physical characteristics of the environment that can stand in for direct measurement

• Observe annual ice layers, annual sediment vares, annual tree rings , annual coral bands, pollen spores

Foraminifera

• Difference species prefer different temps; very narrow range of tolerance; fossilizes well; sedimentary layers of ocean floor

Ice Cores

• Data from 500,000 years

• Air bubbles trapped each year as layers of ice laid down

• Ice in warmer temps have more O-18 isotope

• For 1/2 mil years, CO2 has never been above 300 ppm; last 60 has risen to >400

• Methane + N2O levels also increased

The Poles and Positive Feedback loop

• Poles warm the ice, snow will melt= less solar radiation will be reflected by white surfaces back into space= more solar radiation is absorbed in polar regions and they will warm faster

• As the snow/ice melt= loss of habitat for organism

• Thawing of polar areas also leads to the decomposition of large quantities of frozen biomass = releases methane and further adds to the increased rate of climate change

What causes CO2/temp shifts before humans?

• Path of orbit/position relative to sun

• Orbital tilt

• null

9.6 Ocean Warming

Polar Ice melting

• Sea level rise

• Polar bear habitat

Glaciers melting

• Lack of water supply

Permafrost melting

• Lakes drain deeper into ground, lose water

• Cause erosion with loss of structural support

• Organic matter decomposes, releases methane

Climate Change in the Oceans

• As global air temp increase from excess GHG, ocean temperatures increase

• Many marine animals are dependent on the temp of the water to regulate the temp of their bodies

  • Temp of ocean increases> organisms subject to extreme metabolic stress and may not be able to metabolize food/reproduce

9.7 Ocean Acidification

• CO2 dissolves in water to form H2CO3 (carbonic acid)

  • CO2 + H2O + CO3 = 2 HCO3

  • 1. Carbon dioxide from the atmosphere is absorbed by the ocean

  • 2. Carbon dioxide reacts with seawater to form carbonic acid; seawater pH is lowered

  • 3. Hydrogen ions released by carbonic acid bind to carbonate to form bicarbonate; carbonate concentrations are decreased, making it difficult for shell forming species to form calcium carbonate

• Dissolves shells/skeletons of marine organisms (crustaceans, molluscs, coral)

Sea Level Rise

• Increasing 3.4 mm per year

• Has risen by 9 in

• By 2100; 7-23 in more

• Total volume increases as land ice melts

• Water expands as it gets warmers (thermal expansion)

  • Effects: flooding of coastal nations and towns, saltwater intrusion into aquifers, increased erosion 

  • 100 mil people live within 3 ft of sea level

Effects on organisms

• Ranges have shifted toward both poles

• Plants flower earlier, birds migrate earlier, insects emerge earlier

• Coral bleaching: range of temp tolerance is small (is not related to ocean acidification)

• Fragmentation that can prevent migration

Future Effects

• Heat waves: increased energy demand, risk of death to poor and elderly, damage to crops and increased irrigation needs

• Cold spells: some may have positive effects, expands range of pest species

• Precipitation patterns: when there's less, crops require more irrigation; when there's more, there is flooding, landslides, erosion

• Storm intensity: ocean warming causes more hurricanes

• Ocean currents: thermohaline circulation- freshwater dilutes ocean, stops saltwater from sinking near greenland

• Effects on humans: relocation/climate refugees; health> heat waves, infectious diseases; tourism> snow, coral reefs

How might climate change have positive effects?

• Fewer deaths, crop damage due to cold

• New habitats become hospitable to humans

• Higher rainfall recharge aquifers, grow crops

Precautionary principle

1. Reduce emissions BY: increase fuel efficiency, renewable energy

2. Carbon sequestration BY: returning agricultural land to pasture/forest; capture CO2 from emissions and pump underground or into ocean

9.8 Invasive Species

Species introduction

• invasive species is any organism that is living outside of its natural habitat.  Some species are able to thrive in habitats they are introduced to and can directly compete with native species.

• Invasive species are often generalist, r-selected species and can out-compete native organisms.  In some cases, this can be catastrophic for native ecosystems. Most of the time invasive species are closely tied to humans and utilize human movement to invade new territories. These species often thrive in ecosystems that are similar to the ones that they developed in.  

Strategies for Control

• A variety of strategies have been developed to control the spread of invasive species that are specific to that organism. 

  • Prevention:  State and country borders are often heavily guarded against the import of vectors that could contain these organisms. Vessels are often decontaminated before entering new areas to prevent spreading. 

• Once organisms are introduced, it can be very difficult or impossible to control their spread. In most cases, the organisms have to be sought out and removed.

Zebra mussels

• mall freshwater mussel native to Russia.  It was accidentally introduced on ships and fishing equipment to lakes and rivers around the world and able to establish in great numbers. Adult zebra mussels can survive for weeks out of the water and would be able to travel on equipment from one lake to another with ease. 

• The U.S. has labeled them an invasive species and put in place regulation to decontaminate boating equipment to prevent further spread. The current infestations have caused millions of dollars in damage due to causing the crash of local species of shellfish as well as spreading deadly bird flu

Cane toad

• large completely terrestrial (land-based) toad native to South and Central America. They were introduced to many tropical islands and Australia on purpose with the idea that they could control beetle numbers on sugar cane farms.  In 1937 Australia introduced over sixty thousand toads to their sugar cane farms. The toads were not successful in controlling the beetle population and instead due to their opportunistic feeding habits decimated native species. The large, fast-breeding toads spread quickly across the country as they did in Hawaii, Puerto Rico and many other tropical habitats. In addition to eating and out-competing smaller native species, cane toads are poisonous and are deadly to predators. 

• The removal or control of cane toad populations has so far been unsuccessful. Traps are likely to catch similar native organisms and would cause more damage than good. Scientists have proposed methods of introducing sterile males that would compete with wild males and in turn drive the population down.  However, the majority of control now is conducted by human removal of toads.

9.9 Endangered Species

9.10 Human Impacts on Biodiversity

Biodiversity is the variety of life in a given area.  Some ecosystems or geographic areas are a host to great biodiversity, like coral reefs and rainforest. These places have many different species of plants and animals all living closely together. While other places naturally have less biodiversity, human activities, especially farming, have created large areas with very little diversity.  

One of the most prominent examples is the rainforest being cut down and replaced with rows and rows of palm trees to farm palm oil. These monocultures can not support the diverse animal life that once lived in the area. Destruction of habitat is the most pressing threat to biodiversity but it is not the only one. The major factors causing a decrease in biodiversity can be abbreviated as HIPPCO:

·      Habitat destruction

·      Invasive species

·      Population growth

·      Pollution

·      Climate change

·      Over exploitation

Conservation

•  preserving the complex relationships that naturally exist. The best way in which to do so is to preserve habitats. Some of the ways this has been accomplished is promoting sustainable land use or restoring land. In addition, fragmented sections of preserved habitat can be connected with wildlife corridors allowing genetic diversity to flow throughout populations. 

• Currently, scientists have documented around 2 million species however they believe that there are likely 8 million or more different species of plants, animals, and fungus.  Without preserving natural ecosystems there will be no way to tell the rate of biodiversity loss with human impact. Currently, we are believed to be in the 6th mass extinction event the Earth has seen.  It is estimated that over half of the populations of animals living on Earth in the 1970s are gone