3.1.1. Greenhouse gases (GHGs)

• Examples: carbon dioxide, water vapor, methane
• GHGs related to atmospheric temperature
• Increase GHGs = increase temperature
• Humans messing with GHG content of atmosphere

3.1.2. Evidence of global warming and greenhouse gas (GHG) increasing

1. measured increase in Earth's mean surface temperatures
   • data exist from 1870s on
   • show increase of 0.3-0.6^oC in last 100 yrs
   • 11 of the hottest years in the last 100 have occurred since 1980
   • 2001 = 5th hottest ever in U.S.
   • 1995 hottest year in last 100
   • Problems with data?
2. increased CO2 in atmosphere = best documented global change
   • atmosphere temp related to CO₂
   • CO₂ measured accurately from 1957
   • increased ~25%
3. Greenland and Antarctic ice core records - 2 paths of evidence
   • Air bubbles trapped in the ice caps record concentrations of stable gasses
     • gas record for last 2000+ years
     • CO₂ concentrations were steady for over 1700 years, then skyrocketed
     • supports recent atmosphere records
   • radioactive ¹⁴C, with a half life of 5730 years, has a background level in atmosphere
     • fossil fuels are millions of years old, so radioactive form is gone
     • if increase is due o burning fossil fuel should see increase CO₂, but dilute ¹⁴C
     • this is observed = most CO₂ increase in atmosphere has been due to burning fossil fuels
4. measured increases in other greenhouse gases since 1976
   • methane
   • chlorofluorocarbons
   • nitrous oxide
5. retreat of alpine glaciers
   • extensive sruvace melting during the last 2 decades
6. high-elevation air temperature records
   • several isolated mountain peaks temp's increased >1^oC during past century
7. tropical freezing heights
   • increased freezing-level heights over last 20 years - 4.5 m per year
8. long-term changes in sea surface temperature in the tropics

All say increase in temperature or GHG

3.1.3. Arguments against causes and effects of global warming

• Little argument over the effect greenhouse gases could have on global warming
• Disagreement over: Causes, Amount of warming, Timing (rate of change), implications for life, what to do about it.
• Some criticisms = legitimate distrust of variable results
• Some = misunderstanding methods or interpretation, or desire to have the results be different
• Model predictions of global warming have not been validated by observed increases in temperature, or by smaller than expected increases.
• Models are wrong
• Even if temperatures increase a few degrees, this is less than nightly fluctuations and yearly fluctuations - what's the big deal?
• Even though the temperature is increasing, there is no demonstrated direct link between temperature changes and variation in greenhouse gases concentrations.
• Some people (including some scientists) have argued that warming will be beneficial as long as it is slow enough for crops to adapt.
• Most of the results are from computer models. Models are simplifications of the real world and will give you whatever result you want.
• Without greenhouse gases the Earth would be too cold to inhabit. Therefore, more greenhouse gases probably will make things even better.
• Even if global warming were true, and it is caused by greenhouse gases, there is nothing reasonable that we can do about it.
• Low credibility of scientists.
• Warming due to sunspots!

However, most scientists agree that

• there is a warming trend
• GHGs are a cause
• humans are increasing GHGs

3.1.4. Human-related sources of GHGs

1. CO2
   • burning fossil fuels and forests
2. Methane
   • rice paddies, cattle and sheep (fermentation, animal waste), coal mining, natural gas, biomass burning, landfills
3. Nitrous oxide (N20)
   • burning coal, forests, breakdown of N fertilizers, nylon production, rice paddies
4. CFCs - chlorofluorocarbons
   • up to 5000X the radiating force of CO2
   • leaking refrigerators and air conditioners, evaporation of industrial solvents, plastic foam production, aerosol propellants

3.1.5. Consequences of global warming and greenhouse gas emissions

Some PREDICTED and some OBSERVED:

1. Observed warming and rainfall pattern alteration - predicted
   • global precipitation should increase by 10-15%
   • become more uneven spatially and temporally - floods and drought
   • projections of 3-5^oC warming in temperate regions, up to 18^oC in polar regions
2. Increased soil erosion due to more concentrated rainfall and expanded irrigation - predicted
3. Sea level rise - observed
   • global sea levels have been rising for the past 100 years (1-2 mm annually)
4. Melting polar ice caps
5. Coral reef bleaching - observed = expelling algal symbiont
   • due to increased water temperature
   • leads to reduced photosynthesis, biochemical dysfunction, and failure to grow
6. Other observed consequences (1999-2001)
   • 20/50 species of frogs and toads disappeared from a 30 km2 tropical mountain-tops in Costa Rica
   • crop growing season extended 11 days in Europe, 1959-1993
   • poleward shifts in butterfly and bird species' geographical ranges
   • earlier egg laying in wild birds in temperate zone
   • fresh water lakes appearing in Arctic

Parmesan & Yohe - 2003. Parmesan C, Yohe G. A globally coherent fingerprint of climate change impacts across natural systems. Nature. 2003 Jan 2;421:37-42.

• Reviewed literature on effects of climate change on biodiversity
• >1700 species
• Looked for:
  • range shifts
  • advancement of spring events
• Found
  • Significant range shifts averaging 6.1 km / decade towards the poles
  • Significant mean spring advancement by 2.3 days per decade
  • 279 species exhibit changes with 'very high confidence' due to climate change (IPCC criteria)
  • IPCC = Intergovernmental Panel on Climate Change http://www.ipcc.ch/

3.1.6. Bottom Lines on Global Warming

• Earth is warming
• GHG emissions are increasing
• Ecological effects are being observed
• still controversies over:
  • how much atmosphere will warm local cooling?
  • how much of the warming due to increase in GHGs?
  • what should be done?
  • how fast?
  • who should pay?

6.1.1. Edge Effects

affect species persistence

Edge occurs at ecotones = where 2 habitat types abut

General edge factors:

• where habitat types meet, more species are present = increase in predation and competition
• where habitat types meet, there are abiotic intrusions into the interior habitat

=> the result of habitat fragmentation is interior habitat gets smaller; species that require interior habitat types are most affected

Sao Paulo, Brazil: Atlantic Coastal Rainforest

• in 1500 - 82% forest coverage
• in 1973 - 8% forest coverage

6.1.2. Solutions for Preserving Species?

• Reserves, with buffers
• Where? Depends on what the reserve is for
  e.g., save maximum diversity = on hotspots, save particular species?
• Bigger = better
  • bigger populations
  • more species
• Connectivity
  • rescue populations
  • colonization after local extinction

Reserve Design "rules" based on

• Island Biogeography Theory
• Edge effects
• Protecting habitat-interior specialists

What configuration? Shape? Corridors?

Depends on goal - e.g., if interior species, round; if edge species, linear

Potential problem with corridors / connectivity of populations?

• Spread of emerging and re-emerging diseases
• Corridors as 'ecological traps'
• Disrupting local adaptations
• Spread of exotic, invasive species

6.1.3. Ecosystems

Group of interacting organisms (community) within physical environment at given point in time; includes species, processes (abiotic and biotic), and structure.

• no fixed boundaries - no matter where you draw the border to an ecosystem, there is an 'outside' that influences it e.g., many animals move, water comes from outside sources
• spatial area differs depending on what species are being considered e.g., pitcher plant vs. vernal pool vs. watershed
• disagreement over conservation focus - processes? hot spots? endangered species?

Are communities balanced? Kind of - it depends on:

• Definition of balance
• Time frame
• Degree of disturbance

Concern = assuming communities will recover

Communities tend to persist

Despite deaths of individuals within a community, a tropical forest tends to remain a tropical forest, and grasslands tend to remain grasslands.

• resilience = ability to recover from alteration
• persistence = ability to resist being altered
• constancy = keeping population numbers within bounds

Does species diversity per se matter? YES - work from Tilman et al.

• grassland plants - increase diversity a little, and primary productivity increases
• above-ground biomass after 2-yr drought = higher for more species-rich communities

In theory - work from Ostfeld et al.

• increased species diversity of disease hosts
• = increased # species with low disease competence ( = their probability of transmitting the infection from host to vector)
• = "dilute" the effect of competent reservoirs = reduce persistence in environ and spread to humans

Ecological 'services' are associated with processes e.g., Maintaining atmospheric quality & regulating climate , regulating supplies of fresh water and controlling flooding, detoxifying and disposing of wastes

1 part = Food Webs / Pyramids = The way people have schematically represented who eats whom in an ecosystem is a food web, which is a bunch of food chains. It is a model - the real world is much more complicated.

Community Structure/Trophic Levels:

Actually much more complicated.

Along with food webs, there are other interactions important to conservation biology: predation competition, symbiosis - tight relationship between 2 species:

• parasitism - 1 species benefits, 1 harmed
  • large blue butterfly
  • cattle tick (Boophilus microplus)
• commensalism - 1 species benefits, the other not affected
  • oxpecker
  • remora
• mutualism - both species benefit
  • yucca - moth
  • Clark's nutcracker

Complications?

• Understanding colonization patterns
• Must save both parts
• Different physiological tolerances – climate change
• Consequences of management actions

Semi-Myth: Ecosystems are Fragile

All species are NOT created equal. Keystone species: a species whose effect on the ecosystem is disproportionately large relative to its abundance or biomass.

Being a keystone

• alter structure of the environment e.g., woodpeckers, beaver, gophers, termites, leaf cutter ants ecosystem engineers
• drive energy flow of environment e.g., exotic species, provides food for many species during critical time of year, predators that drive prey diversity

Identifying keystone species:

• experimental removal is best, but often not possible
• comparative studies less powerful - sites with and without the species
• descriptive least powerful, but necessary (need to know your species)

6.2.1. Biological control - Trying to control rats in Micronesia

• good / bad refers to human interests; solid line who at what (eaten is what is pointed to)
• dashed line = should have eaten, did not