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Honors Biology Chapter 36 Environmental Concerns John Regan Wendy Vermillion 36-1 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 36.1 Human use of resources • Overview – Resource- biotic or abiotic factor that helps meet basic needs • Nonrenewable resource- can’t be replaced by nature, limited in supply – Amount of land – Fossil fuels, metals – Can be recycled • Renewable resource- can be replaced by nature, not limited, but must not be wasted – Water – Solar energy – Plants and animals for food • Sustainable use - use resources at a rate that will not deplete them – Pollution- alteration of the environment in an undesirable way – Human impact is proportional to size of population 36-2 Resources • Fig. 36.1 36-3 Human use of resources cont’d. • Land – Worldwide currently >32 persons per square kilometer 1. Beaches and human habitation • Leads to erosion and loss of habitat for marine organisms • Erosion – 70% of world’s beaches are eroding – Often result of human factors » Global warming » Sea wall construction, groin construction » Filling in of wetlands – US shorelines lose 40% more sediment than receive • Coastal pollution – Toxic substances travel downstream to sea – oil 36-4 Beach erosion • Fig. 36.2 36-5 Human use of resources cont’d. • Land cont’d. 2. Semiarid lands and human habitation 40% of earth’s land is desert • Desertification- conversion of semiarid land to desert – Can result from overgrazing by livestock, farming, or removing plants for fuel 3. Tropical rainforest and human habitation • Deforestation- causes loss of soil nutrients and fertility – Danger of desertification • Loss of biodiversity- tropical rain forest has greatest biodiversity of any biome 36-6 Desertification • Fig. 36.3 36-7 Deforestation • Fig. 36.4 36-8 Human use of resources cont’d. • Water – Most water worldwide is used in agriculture and industry and not for drinking – Irrigation-intensive agriculture-40% of world’s food crops – Dams • 45,000 dams worldwide trap 14% of all precipitation runoff • Disrupt flow of rivers- many barely reach sea • Disadvantages to dams – Evaporation and seepage into ground rock – Increased concentration of salt from evaporation can make downstream water unusable – Silt buildup decreases reservoir size – Habitat loss 36-9 Freshwater resources • Fig. 36.5 36-10 Human use of resources cont’d. • Water cont’d. – Aquifers • Hold approximately 1000 times as much water as falls on land as precipitation each year • People have begun tapping into aquifers as a source of water when surface waters become depleted – Environmental consequences • Subsidence- settling of soil as it dries out from lack of groundwater – Creates sinkholes • Saltwater intrusion- as water table lowers sea water can back up into streams and rivers – Reduces supply of freshwater along the coasts 36-11 Human use of resources cont’d. • Water cont’d. – Conservation of water • Planting drought-resistant and salt-tolerant crops • Drip irrigation – Saves 50% over traditional methods – Used on less than 1% of irrigated land – Governments subsidize irrigation so farmers have little incentive to use drip irrigation • Using conservation methods and reusing water could help world’s industries cut water demands by MORE THAN HALF! 36-12 Human use of resources cont’d. • Food – 6 billion people on Earth and only enough food to provide 2,500 calories per person per day – Food comes from 3 activities- growing crops, raising animals, and fishing – Biggest increase in food production has come from modern farming methods- include some harmful practices • Planting of few genetic varieties (monoculture)- means all could be wiped out by same diseases, parasites, etc. • Heavy use of fertilizers, herbicides, pesticides-runoff-water pollution can kill off desirable species as well as cause pollution • Generous irrigation- consumes water • Excessive fuel consumption- transform fossil fuel energy into food energy 36-13 Human use of resources cont’d. • Food cont’d. – Soil loss and degradation • • • • Loss of topsoil Single row crop planting Eroded soil and chemicals end up in water Salinization – Green revolutions • Tropical wheat and rice varieties that grow well in climates of LDCs • Dramatic increases in yields- green revolution • BUT- these crops are “high responders”- need irrigation, fertilizers, pesticides – Require same subsidies and create same ecological problems as modern farming methods 36-14 Conservation methods • Fig. 36.6 36-15 Human use of resources cont’d. • Genetic engineering – Can produce transgenic plants • • • • Herbicide and drought resistant Less tillage, less water use, less soil loss More nutrients Some are opposed- possible damage to ecosystem? 36-16 Human use of resources cont’d. • Food cont’d. – Domestic livestock • MDCs – Diet contains more than enough protein – Livestock account for most of the energy expenditure in agriculture » 2/3 of cropland is used to grow feed » Fossil fuel, fertilizer, water, herbicides, pesticides » Pollution, energy, and water intensive – 10 calories of energy in plant tissue 1 calorie of energy for production of tissue in herbivore » Can feed 10 times as many people on grain as meat 36-17 Human use of resources cont’d. • Food cont’d. – Fisheries • Increased efficiency of fishing has caused over-fishing of specific species • Impacts biodiversity as “undesirable” marine organisms are also caught in fish nets – These are disposed of • World’s shrimp fishery has an annual catch of 1.8 million tons caught and in the process 9.5 million tons of other animals caught in the nets were destroyed 36-18 Fisheries • Fig. 36.7 36-19 Human use of resources cont’d. • Energy – Nonrenewable sources • 6% of world’s energy comes from nuclear power – People are concerned of possible danger of meltdown – Disposal of radioactive waste is a problem • 75% from fossil fuels – Oil burns cleaner that coal – All fossil fuels emit pollution into the air when burned – US uses > ½ fossil fuels – Fossil fuels and global climate change – Greenhouse gases- carbon dioxide, methane are examples » Do not allow infrared heat to escape back to space » Global warming effect 36-20 Human use of resources cont’d. • Energy cont’d. – Renewable energy sources • 2 types commonly used – Hydropower - 10% electricity in US » Small dams as opposed to large dams – Geothermal power » From radioactive decay of elements in ground • Other types may be used more in the future – Wind-generated – electricity » Migratory birds – Solar power » Passive- south facing windows » Photovoltaic (solar) cell- electricity » Advantages- less dependent on foreign oil - cleaner 36-21 Hydropower • Fig. 36.8 36-22 Other renewable energy sources • Fig. 36.9 36-23 Human use of resources cont’d. • Minerals – Nonrenewable raw materials – Fossil fuels, metals, nonmetals – Being depleted at a rapid rate – Strip mining • • • • Leaves land devoid of vegetation and top soil Toxic wastes washed into streams and rivers Law now requires reclamation of land Heavy metals- dangerous to human health – Lead, arsenic, cadmium, tin, chromium, zinc, copper – Found in batteries, paints, etc.-careful disposal is critical! 36-24 Modern mining capabilities • Fig. 36.10 36-25 Human use of resources cont’d. • Synthetic organic compounds – Used in making plastics, pesticides, herbicides, cosmetics Halogenated hydrocarbons- halogens (chlorine, bromine, fluorine) have replaced hydrogen in chemical structure • CFCs- chlorofluorocarbons – Involved in thinning of the ozone shield – Increases the amount of solar radiation Earth’s surface receives – Legislation passed to prevent production of any more CFCs – Many pesticides • DDT 36-26 Human use of resources cont’d. • Wastes – Early 1970’s- legislation passed to prevent venting wastes into the air • As a result, most wastes are buried in landfills • Top most commonly found contaminants – Lead, arsenic, cadmium, chromium, trichloroethylene, toluene, benzene, polychlorinated biphenyls (PCBs), chloroform – Endocrine-disrupting contaminants • Interfere with normal hormone function • Occur at levels 1000 times greater that the concentration in blood 36-27 Human use of resources cont’d. • Wastes cont’d. – Sewage • Raw sewage depletes oxygen levels in lakes and rivers – Decreases diversity of organisms – Feces can contain human pathogens- cholera, typhoid fever, dysentery • Treatment plants use bacteria to break down raw sewage – Broken down to inorganic nutrients- nitrates, phosphates – Released into surface waters » Can cause eutrophication 36-28 Human use of resources cont’d. • Wastes cont’d. – Industrial wastes • Biological magnification – Decomposers cannot break them down – Accumulate in their tissues – Amplified as you move up the food chain • Humans are final consumers – Human milk in some areas contains DDT, PCBs – Mercury in fish – Pollution control measures are the best way to address the problem. 36-29 36.2 Impact on biodiversity Biodiversity- variety of life on earth, # species Causes: 1. Habitat loss – Most frequent cause of extinction – Has occurred all over biosphere, but concern is focused on tropical rain forests and coral reefs • Areas of high biodiversity • Rainforests reduced from 14% of landmass to 6% • 60% of coral reefs have been destroyed – May be completely gone in 40 years! 36-30 Loss of biodiversity • Fig. 36.11 36-31 Impact on biodiversity cont’d. 2. Alien species – Nonnative members of an ecosystem – Introduced by • Colonization – Dandelion from England • Horticulture and agriculture – Kudzu vine from Japan • Accidental transport – Zebra mussels, Dutch elm disease, Asian longhorn beetle, Asian carp – Exotics on islands • Particularly susceptible to environmental disruption by alien species • Native species are specially adapted to each other and cannot compete 36-32 Alien species • Fig. 36.12 36-33 Impact on biodiversity cont’d. • Pollution – Acid deposition • Weakens trees and makes them susceptible to disease, insects • Kills organisms in lakes – Eutrophication • Over-enrichment of lakes by inorganic nutrients • Agricultural runoff, wastes • Algae blooms, decomposers break them down – Oxygen depleted and fish die – Global warming • From greenhouse gases • Destruction of wetlands as seas rise, shift in temperature so that species cannot survive, die off of coral reefs 36-34 Global warming and coral reefs • Fig. 36.13 36-35 Impact on biodiversity cont’d. • Pollution cont’d. – Ozone depletion • Release of CFCs causes ozone shield to break down – Impairment of crop and tree growth, death of plankton – Organic chemicals • Many are endocrine-disrupting contaminants • Affect the endocrine system and reproductive potential 36-36 Impact on biodiversity cont’d. • Overexploitation – Occurs when number of individuals taken from wild population is so great that population numbers become severely depleted – Positive feedback- the more depleted a population, the more valuable its members become which is an incentive to capture the few remaining organisms – Increased efficiency of fishing has caused depletion – Mammalian species hunted for hides, horns, tusks, bones • Disease – Wildlife exposed to new diseases and domestic species due to human encroachment – Zoo animals are exposed to other exotic species they would not ever be near in the wild- another source of new disease exposure 36-37 Wildlife is at risk due to disease • Fig. 36.15 36-38 36.3 Value of biodiversity • Direct value-various wildlife species perform services for human beings – Medicinal value • Rosy periwinkle – treat cancer • Predict another 328 drugs yet to be found in tropical rain forest – Agricultural value • Crops derived from wild plants – Biological pest control – Pollinators - bees – Consumptive use value • Fish, shellfish • Wild fruits and vegetables, skins, fibers, seaweed, meat 36-39 Direct value of wildlife • Fig. 36.16 36-40 Value of biodiversity cont’d. • Indirect value- more economical to save ecosystem in which species lives rather than the individual species – Ecosystems perform many services for humans • • • • • • Biogeochemical cycles - efficient recycling Waste disposal - purify water Provision of fresh water - hold water, prevent flooding Prevention of soil erosion Regulation of climate - shade, take in CO2 Ecotourism 36-41 36.4 Working toward a sustainable society • Today’s society is not sustainable because – Considerable portion of land, and therefore ecosystems, is used for human purposes – Agriculture requires input of large amounts of nonrenewable resources – At least half of the agricultural yield in the U.S. goes toward feeding animals • Takes 10 pounds of grain to make 1 pound of meat – We are running out of available fresh water • Using it faster that it can be renewed – Our society uses primarily nonrenewable fossil fuels for energy • Global warming, acid precipitation, smog – Minerals are nonrenewable, and use of products causes much pollution 36-42 Human society at present • Fig. 36.17 36-43 Working toward a sustainable society cont’d. • Characteristics of a sustainable society – Natural ecosystem can offer clues • Uses only solar energy • Materials cycle through various populations back to producers – We need to use renewable energy sources and recycle materials – Growing populations of the LDCs as well as the over consumption by the MDCs put a strain on the environment 36-44 Working toward a sustainable society cont’d. • Assessing economic well-being and quality of life – Currently gross national product (GNP) is used to measure flow of money from consumers to businesses • Takes into account only economics and not any potentially harmful side effects • Also does not take into account damage to the environment • Need new index which takes nonmonetary values into account – Measuring nonmonetary values • Better at revealing quality of life than GNP • Index of Sustainable Welfare (ISW) includes – Real per capita income – Distributional equity – Natural resource depletion – Value of unpaid labor 36-45 Working toward a sustainable society cont’d. • Assessing economic well-being and quality of life cont’d. – Genuine Progress Indicator (GPI)- another quality of life index – Both the ISW and the GPI suggest that the quality of life has gone down, even though the GNP has gone up – Ecological economists are still trying to devise a way to measure • • • • Use value-actual price we pay to use goods Option value- preserving options for the future Existence value- saving things we may not realize exist yet Aesthetic value- appreciating an area for its beauty or contribution to biodiversity • Cultural value-language, mythology, history important for cultural identity • Scientific and educational value- valuing knowledge of naturalists 36-46 Sustainable society • Fig. 36.18 36-47