F Human Impact

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ch Population Change and Population Density In density-independent populations, birth rate and death rate do not change with population density In density-dependent populations, birth rates fall and death rates rise with population density

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Density-Dependent Population Regulation Density-dependent birth and death rates are an example of negative feedback that regulates population growth They are affected by many factors, such as competition for resources, territoriality, disease, predation, toxic wastes, and intrinsic factors

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Competition for Resources In crowded populations, increasing population density intensifies competition for resources and results in a lower birth rate

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig B.C.E B.C.E B.C.E C.E The Plague Human population (billions) 7 Concept 53.6: The human population is no longer growing exponentially but is still increasing rapidly No population can grow indefinitely, and humans are no exception – The human population increased relatively slowly until about 1650 and then began to grow exponentially

Fig Projected data Annual percent increase Year Though the global population is still growing, the rate of growth began to slow during the 1960s

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Regional Patterns of Population Change To maintain population stability, a regional human population can exist in one of two configurations: – Zero population growth = High birth rate – High death rate – Zero population growth = Low birth rate – Low death rate The demographic transition is the move from the first state toward the second state

Fig Year 1850 SwedenMexico Birth rate Death rate Birth or death rate per 1,000 people

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The demographic transition is associated with an increase in the quality of health care and improved access to education, especially for women Most of the current global population growth is concentrated in developing countries

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Age Structure One important demographic factor in present and future growth trends is a country’s age structure Age structure is the relative number of individuals at each age

Fig Rapid growth Afghanistan MaleFemaleAge MaleFemale Slow growth United States MaleFemale No growth Italy –84 75–79 70–74 60–64 65–69 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 0–4 5–9 10– –84 75–79 70–74 60–64 65–69 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 0–4 5–9 10– Percent of population

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Age structure diagrams can predict a population’s growth trends They can illuminate social conditions and help us plan for the future

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Global Carrying Capacity How many humans can the biosphere support? – The carrying capacity of Earth for humans is uncertain – The average estimate is 10–15 billion

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ch. 55.5: Human Impact on chemical cycles Humans release many toxic chemicals, including synthetics previously unknown to nature In some cases, harmful substances persist for long periods in an ecosystem One reason toxins are harmful is that they become more concentrated in successive trophic levels Biological magnification concentrates toxins at higher trophic levels, where biomass is lower

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Many pesticides such as DDT are subject to biological magnification in ecosystems In the 1960s Rachel Carson brought attention to the biomagnification of DDT in birds in her book Silent Spring

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig Lake trout 4.83 ppm Concentration of PCBs Herring gull eggs 124 ppm Smelt 1.04 ppm Phytoplankton ppm Zooplankton ppm

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Greenhouse Gases and Global Warming One pressing problem caused by human activities is the rising level of atmospheric carbon dioxide Due to the burning of fossil fuels and other human activities, the concentration of atmospheric CO 2 has been steadily increasing

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig CO 2 CO 2 concentration (ppm) Temperature Average global temperature (ºC) Year

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Greenhouse Effect and Climate CO 2, water vapor, and other greenhouse gases reflect infrared radiation back toward Earth; this is the greenhouse effect This effect is important for keeping Earth’s surface at a habitable temperature Increased levels of atmospheric CO 2 are magnifying the greenhouse effect, which could cause global warming and climatic change

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Increasing concentration of atmospheric CO 2 is linked to increasing global temperature Northern coniferous forests and tundra show the strongest effects of global warming A warming trend would also affect the geographic distribution of precipitation

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Global warming can be slowed by reducing energy needs and converting to renewable sources of energy Stabilizing CO 2 emissions will require an international effort

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Depletion of Atmospheric Ozone Life on Earth is protected from damaging effects of UV radiation by a protective layer of ozone molecules in the atmosphere Satellite studies suggest that the ozone layer has been gradually thinning since 1975

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ozone layer thickness (Dobsons) Fig Year ’ ’95’90’85 ’80 ’75’70 ’65 ’

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Destruction of atmospheric ozone probably results from chlorine- releasing pollutants such as CFCs produced by human activity Fig O2O2 Sunlight Cl 2 O 2 Chlorine Chlorine atom O3O3 O2O2 ClO

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings (a) September 1979(b) September 2006 Scientists first described an “ozone hole” over Antarctica in 1985; it has increased in size as ozone depletion has increased

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ozone depletion causes DNA damage in plants and poorer phytoplankton growth An international agreement signed in 1987 has resulted in a decrease in ozone depletion

Ch. 56 Biodiversity crisis F Extinction ~ natural phenomenon, however, rate is of concern….. F 50% loss of species when 90% of habitat is lost

Major Threats to Biodiversity F Habitat destruction ~ single greatest threat; species designation as extinct, endangered, vulnerable, rare; 93% of coral reefs F Competition by exotic (non- native) species ~ cause of species designation as extinct, endangered, vulnerable, rare; travel F Overexploitation ~ commercial harvest or sport fishing; illegal trade

Biodiversity: Human welfare F 25% of all medical prescriptions F Genetic variability F Aesthetic and ethical reasons F Species survival

Conservation biology focus F Preservationism: setting aside select areas as natural and underdeveloped F Evolutionary / ecological view: natural systems result from millions of years of evolution and ecosystem processes are necessary to maintain the biosphere

Geographic distribution of biodiversity F Energy availability ~ solar radiation F Habitat heterogeneity ~ environmental patchiness F Niche specialization ~ narrow resource range specialization F Population interactions ~ complex population interactions

Population & species level conservation F Biodiversity hot spot: small area with an exceptional concentration of species F Endemic species: species found nowhere else F Endangered species: organism “in danger of extinction” F Threatened species: likely to become endangered in the foreseeable future

Human Impact F Biological magnification: trophic process in which retained substances become more concentrated at higher levels F Ozone depletion: effect of chlorofluorocarbons (CFC’s) released into the atmosphere F Rainforest destruction F Cause: Overpopulation?

Air Pollution F Major contributions: –CO 2, CFCs, etc. F Smog –Thermal inversion traps pollution F Acid Rain F Ozone Thinning –CFCs convert O 3 into O 2 by reconfiguration of bonds –Leads to increased incidence of ultraviolet radiation

Waste Management F Density- dependent factor that limits space available for other purposes F Green revolution- can we improve already existing agricultural lands rather than create more?

Deforestation F Effects of deforestation: –Reduced productivity –Increased erosion due to lessening of root structures –Sediment build up –Increase in CO 2

F Most water on earth is unusable (salt content) F Desalination- conversion of salt water into freshwater (energetically costly) F Agriculture accounts for massive water use worldwide F Water pollution F Legislative measures may influence water use Water considerations

F Sixty-six percent of a human being is water. F Seventy-five percent of the human brain is water. F Seventy-five percent of a living tree is water. F You could survive about a month without food, but only 5 to 7 days without water. F On the average, each American uses about 160 gallons of water a day at a cost of 27 cents. F Bottled water may cost up to 1000 times more than municipal may not be as safe. F Two-thirds of the water used in an average home is used in the bathroom. F Typically 4 to 6 gallons of water are used for every toilet flush. F On the average, a person uses 2 gallons of water to brush his or her teeth each day. F A 10-minute shower uses about 55 gallons of water. F A leaking faucet can waste up to 100 gallons of water a day. Water Facts

Energy Consumption F Disappearance of non- renewable fuel sources could be our biggest coming ecological issue F Non-renewable Sources –Fossil fuels (coal, petroleum, nat. gas) –Nuclear Energy F Alternative Sources 1.Solar-Hydrogen 2.Wind 3.Fusion