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Community Ecologyand Ecosystems
Chapter 53
Ecological communities are composed of all species populations that cohabit an area
An ecosystem is an ecological communityand its abiotic environment
Are species distributed individualistically? Or are communities composed of coevolved, interactive
assemblages?
Is Global Warming Happening?Is Global Warming Happening?
A Very Controversial TopicA Very Controversial Topic
Must know the agenda of Must know the agenda of
“authorities”“authorities”
Must know the Must know the agenda of “authorities”...agenda of “authorities”...
There areThere are 3 schools of thought:3 schools of thought:
1. This is an environmental emergency requiring immediate action1. This is an environmental emergency requiring immediate action
2. The reality of global warming, or at least the human influence 2. The reality of global warming, or at least the human influence requires better research before initiating expensive interventionsrequires better research before initiating expensive interventions
3. Economic factors require the highest priority,3. Economic factors require the highest priority,subordinating environmental considerations subordinating environmental considerations
Is Global Warming Happening?Is Global Warming Happening?• The three warmest years on record are 1998, 1997, 1995• The three warmest years on record are 1998, 1997, 1995
• 1998 may have been the warmest year in 1200 years• 1998 may have been the warmest year in 1200 years
• The last two decades have been the warmest in 1200 years• The last two decades have been the warmest in 1200 years
• The spring green wave occurs about 6 days earlier than 1959• The spring green wave occurs about 6 days earlier than 1959
• Autumn brown wave are delayed by about 5 days compared to 1959• Autumn brown wave are delayed by about 5 days compared to 1959
• The frequency of extreme weather is increasing in some places• The frequency of extreme weather is increasing in some places
• Ice caps and glaciers are retreating, permafrost is melting• Ice caps and glaciers are retreating, permafrost is melting
• Temperate species ranges are moving to higher latitudes• Temperate species ranges are moving to higher latitudes
• Oceans levels are rising …with alarming implications• Oceans levels are rising …with alarming implications
Over the last 1000 years, temperatures have been decreasing somewhat, until about the advent of the industrial revolution. Since then
temperature has increased.
Effects on agriculture
• Agricultural productivity has increased 8% more than population growth since WW II
• U.S. agricultural production has played a major role
• Factors:a) Plant breedingb) Energy subsidiesc) Great climate and great soils geographically superimposed
Ice melting - Ocean level rises
• Several Pacific islands already submerged
• Maldives, Bangladesh threatened
• US low-lying areas threatened
• Worst scenario ...increase of 4° C would melt ice caps and raise oceans 200-400 feet, placing all agricultural regions and all big cities except Mexico City under water …as destructive as nuclear war
IPCCU.N Intergovernmental Panel on Climate Change
• IPCC was formed in response to growing scientific consensus that global climate changes might be occurring
• 1995 IPCCa) The most definitive scientific statement about global warmingb) Confirmed that global warming is happeningc) Concluded that human influence is implicated
• Uncertainty factors:a) Relative impact of natural and human causesb) How rapidly warming will occurc) How severe the warming will bed) Where it will be most pronounced
How Is Global Warming How Is Global Warming Happening?Happening?
Greenhouse effects resulting from Greenhouse effects resulting from
human increases in greenhouse gasses human increases in greenhouse gasses
Greenhouse EffectGreenhouse Effect
Radiation is always converted to a longer
wave length when moving through a denser medium
Lightshort-wave radiation Heat
long-wave radiation
Principle Greenhouse Gasses
• Carbon Dioxide (CO2 ), from combustion & deforestation
• Methane (CH4 ), from natural and man-made causes
• Nitrous oxide (N2O ), from pollution
• Chlorofluorocarbons (CFCs), from air conditioners * refrigerators
• Ozone (O3 ), from pollution and natural causes
CO2 and temperature changes over the last 50 years are correlated - suggesting but not proving possible causation
Over an even longer time period, 400,000 years, CO2 levels have oscillated on a grand scale, but the recent increase in CO2 levels seems
unique over this time period.
Some pollutants cool the atmosphere by blocking light from entering
• Aerosols of some pollutants can do this(e.g., sulfur emissions from industry and volcanic activity)
• Effects short-term(particles suspended for days or weeks, versus GH gasses lasting hundreds of years)
• Only works during day time(versus GH gasses that re-radiate heat day and night)
• Cooling effect of aerosols < Heating effect of GH gasses
The ozone hole 10 September 2000The first major city is exposed in southern Chile
What are the effects of increased UV radiation?
An increased incidence of skin cancers? Other?
International Congresses• Kyoto …western nations, especially US avoided
real sacrifice
• Hague, fall 2000 US influence emphasizes economy
• reforestation efforts to counteract CO2 without reducing CO2 emissions
• Buying credits from other countries CO2 emission controls without reducing US emissions
• US not taxing energy, encouraging energy use and production
8 major US environmental groups may boycot meetings in protest of US policies
Is Global Warming Happening?Is Global Warming Happening?• The three warmest years on record are 1998, 1997, 1995• The three warmest years on record are 1998, 1997, 1995
• 1998 may have been the warmest year in 1200 years• 1998 may have been the warmest year in 1200 years
• The last two decades have been the warmest in 1200 years• The last two decades have been the warmest in 1200 years
• The spring green wave occurs about 6 days earlier than 1959• The spring green wave occurs about 6 days earlier than 1959
• Autumn brown wave are delayed by about 5 days compared to 1959• Autumn brown wave are delayed by about 5 days compared to 1959
• The frequency of extreme weather is increasing in some places• The frequency of extreme weather is increasing in some places
• Ice caps and glaciers are retreating, permafrost is melting• Ice caps and glaciers are retreating, permafrost is melting
• Temperate species ranges are moving to higher latitudes• Temperate species ranges are moving to higher latitudes
• Oceans levels are rising …with alarming implications• Oceans levels are rising …with alarming implications
Must know the Must know the agenda of “authorities”...agenda of “authorities”...
There areThere are 3 schools of thought:3 schools of thought:
1. This is an environmental emergency requiring immediate action1. This is an environmental emergency requiring immediate action
2. The reality of global warming, or at least the human influence 2. The reality of global warming, or at least the human influence requires better research before initiating expensive interventionsrequires better research before initiating expensive interventions
3. Economic factors require the highest priority,3. Economic factors require the highest priority,subordinating environmental considerations subordinating environmental considerations