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Community Ecology and Ecosystems Chapter 53 Ecological communities are composed of all species populations that cohabit an area An ecosystem is an ecological community and its abiotic environment Community Ecology Communities are composed of all of the species that cohabit an area. Are species distributed individualistically? Or are communities composed of coevolved, interactive assemblages? Succession Competitive Exclusion No two species can occupy the same niche at the same site Galapagos Finches Character Displacement Ecosystems Food Chains Food Webs Primary Productivity Energy Flow and Energy Pyramids Energy Flow Numbers of Individuals per Trophic Level Human Effects on the Environment Ecological Magnification Forests rely on their nutrient pools, which can be leached away after deforestation. Acid Deposition Greenhouse Effect Global Warming Our fragile atmosphere atmosphere Is Global Warming Happening? Is Global Warming Happening? A Very Controversial Topic Must know the agenda of “authorities” Must know the agenda of “authorities”... There are 3 schools of thought: 1. This is an environmental emergency requiring immediate action 2. The reality of global warming, or at least the human influence requires better research before initiating expensive interventions 3. Economic factors require the highest priority, subordinating environmental considerations Is Global Warming Happening? • The three warmest years on record are 1998, 1997, 1995 • 1998 may have been the warmest year 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 • Autumn brown wave are delayed by about 5 days compared to 1959 • The frequency of extreme weather is increasing in some places • Ice caps and glaciers are retreating, permafrost is melting • Temperate species ranges are moving to higher latitudes • 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. Melting of the permafrost in Alaska Global Climate Change Range Alterations Global Climate Change Models Global Climate Change Models - Critical Need: Data 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) b) c) Plant breeding Energy subsidies Great climate and great soils geographically superimposed The American Breadbasket good soils and good climate The American Breadbasket under global warming good climate moves to the SW over poor soils 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 US Flooding with 1 meter rise in water level IPCC U.N Intergovernmental Panel on Climate Change • IPCC was formed in response to growing scientific consensus that global climate changes might be occurring • 1995 IPCC a) b) c) • The most definitive scientific statement about global warming Confirmed that global warming is happening Concluded that human influence is implicated Uncertainty factors: a) b) c) d) Relative impact of natural and human causes How rapidly warming will occur How severe the warming will be Where it will be most pronounced How Is Global Warming Happening? How Is Global Warming Happening? Greenhouse effects resulting from human increases in greenhouse gasses Greenhouse Effect Radiation is always converted to a longer wave length when moving through a denser medium Light short-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 levels have been increasing for at least 50 years CO2 concentration over the past half century in Hawaii 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. IPCC Conclusions: Global warming is happening Human influence is implicated 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 Eruption of Mount Pinatubo massive sulfur aerosol emissions in 1991 global cooling in 1992-3 Stratospheric Ozone Layer The ozone hole 10 September 2000 The 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? • The three warmest years on record are 1998, 1997, 1995 • 1998 may have been the warmest year 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 • Autumn brown wave are delayed by about 5 days compared to 1959 • The frequency of extreme weather is increasing in some places • Ice caps and glaciers are retreating, permafrost is melting • Temperate species ranges are moving to higher latitudes • Oceans levels are rising …with alarming implications Must know the agenda of “authorities”... There are 3 schools of thought: 1. This is an environmental emergency requiring immediate action 2. The reality of global warming, or at least the human influence requires better research before initiating expensive interventions 3. Economic factors require the highest priority, subordinating environmental considerations Our fragile atmosphere atmosphere