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The Living World Fourth Edition GEORGE B. JOHNSON 34 Planet Under Stress PowerPoint® Lectures prepared by Johnny El-Rady Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.1 Pollution Damage done to one of the world’s ecosystems can have ill effects on many others Widespread effects on the worldwide ecosystem are termed global change Patterns of global change include Pollution Acid precipitation Ozone hole Greenhouse effect Loss of biodiversity Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Chemical Pollution Major problem because of growth of heavy industry and overly casual attitude in industrialized countries Air pollution Gray-air cities (include New York) Pollutants are usually sulfur oxides emitted by industry Brown-air cities (include Los Angeles) Pollutants undergo chemical reactions in the sunlight Water pollution A serious consequence of our “Flushing it down the sink” attitude Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Agricultural Chemicals The spread of “modern” agriculture introduced large amounts of chemicals into the global ecosystem Pesticides, herbicides and fertilizers Chlorinated hydrocarbons (such as DDT) caused severe environmental problems through biological magnification Become more concentrated as they move up the food chain Fig. 34.1 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.2 Acid Precipitation In the 1950s, tall stacks were introduced to disperse sulfur-rich smoke into winds to disperse and dilute it The problem was exported, not solved! Sulfur combines with water vapor to produce sulfuric acid Natural rain water has a pH of ~ 5.6 In the northeastern US, the pH is ~ 4.3 This pollution-acidified precipitation is called acid rain (acid precipitation) Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.2 Acid Precipitation Acid precipitation destroys life Forests and lake ecosystems in Europe and North America have been seriously damaged The solution is to capture and remove emissions before their release Serious problems in implementation 1. Expensive 2. Polluter and recipient are far from one another Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.3 The Ozone Hole Starting in 1975, the earth’s ozone shield began to disintegrate creating an ozone hole The culprit is a class of chemicals called chlorofluorocarbons (CFCs) They have been used since the 1920s as coolants and aerosol dispensers Are very stable and thus have accumulated in the atmosphere over time Catalyze the conversion of ozone (O3) into oxygen (O2) without being used up Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.3 The Ozone Hole Every 1% drop in ozone content is estimated to lead to a 6% increase in the incidence of skin cancers 11.4-millionsquare-mile hole Hole is largest during Antarctic winter Hole tails off as temperature rises Fig. 34.4 The ozone hole over Antarctica is still growing Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.4 The Greenhouse Effect For over 150 years, our industrial society has been relying on the burning of fossil fuels This has greatly increased atmospheric levels of carbon dioxide (CO2) CO2 transmits radiant energy from the sun, but traps infrared light, or heat This creates what is known as the greenhouse effect Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.4 The Greenhouse Effect The accumulation of CO2 and other “greenhouse gases” (such as CFCs) have led to global warming Fig. 34.5 Average global temperatures could increase from 1oC to 4oC Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.4 The Greenhouse Effect Global warming could have serious effects on 1. Rain patterns Areas experiencing droughts may see even less rain 2. Agriculture The yields of some crops will increase, while the yields of other crops will decrease 3. Sea levels Melting of large stores of ice will cause water levels to rise Increased flooding of low-lying lands Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.5 Loss of Biodiversity > 99% of species known to science are now extinct Current rates of extinction are alarmingly high Conservation biologists have identified three key factors Habitat loss Species overexploitation Introduced species Single most important cause Fig. 34.6 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Habitat loss 1. 2. 3. 4. Destruction Pollution Human disruption Habitat fragmentation Rain forest of Madagascar Species overexploitation Species that are hunted or harvested by humans are at great risk of extinction Fig. 34.7 Introduced species The introduction of exotic species by humans has wiped out or threatened many native populations Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.6 Reducing Pollution Human activities are placing a severe stress on the biosphere Industrial pollution is one of the key problems It results from a failure of our economy to set a proper price on environmental health The reason is money! Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Economists have identified an “optimum” amount of pollution based on the following How much it costs to reduce pollution versus the social and environmental cost of allowing pollution The indirect costs of pollution are usually not taken into account Fig. 34.8 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display In the US, two effective approaches have been devised to curb pollution 1. Antipollution laws All cars are required to have catalytic converters to eliminate automobile smog The Clean Air Act of 1990 requires that power plants eliminate sulfur emissions 2. Pollution taxes In effect, a government-imposed artificial price hike added to the price of production Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.7 Finding Other Sources of Energy Many countries are turning to nuclear power for their growing energy needs In 1995, > 500 nuclear reactors were producing power worldwide In the US, nuclear power plants have not been popular because of 1. Ample access to cheap coal 2. Public fears of the consequences of an accident Three Mile Island nuclear plant in 1979 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Nuclear power can provide plentiful cheap energy However, several problems must be overcome 1. Safe operation Chernobyl accident in 1986 Fears of vast radioactive contamination 2. Waste disposal Spent nuclear fuel remains radioactive for thousands of years 3. Security Fig. 34.10 Fears of terrorists getting their hands on plutonium Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.8 Preserving Nonreplaceable Resources The consumption or destruction of nonreplaceable resources is the most serious problem humans face The key nonreplaceable resources are Topsoil Groundwater Biodiversity Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Topsoil Is being lost at a rate of centimeters per decade The US has lost 1/4th of its topsoil since 1950! Solutions Genetic-engineering to make crops resistant to weed-killing herbicides Terracing to recapture lost topsoil Groundwater Seeped into its underground reservoir very slowly during the last ice age over 12,000 years ago It is being wasted (watering lawns) or polluted Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Biodiversity In the last 20 years, ~ 1/2 of the world’s tropical rain forests have been either burned or cut Animal and plant species are becoming extinct The ancient forests of the Pacific Northwest are being cut at a ferocious rate Loss of species entails three costs 1. Direct economic value of the products 2. Indirect economic value of the benefits 3. Ethical and aesthetic value Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.9 Curbing Population Growth The human population has grown explosively over the last 300 years 6.3 billion in 2003 Fig. 34.13 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Worldwide Birth rate has stabilized to ~ 21 per year per 1,000 people Death rate has fallen to ~ 9 per year per 1,000 people This amounts to a population growth rate of 1.3% per year The world population will double in 54 years! Mexico City One of the most alarming trends is massive movement of people towards urban centers ~ 26 million inhabitants Fig. 34.14 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display The world’s population growth is unevenly distributed among countries Fertility rates will determine world population Fig. 34.15 Growth rate in developed countries is 0.1% per year Growth rate in developing countries is 1.9% per year Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display The world population growth rate has been declining The United Nations attributes the decline to 1. Increased family planning efforts 2. Increased economic power and social status of women Slowing population growth helps sustain resources, but per capita consumption is also important Wealthiest 20% of the world’s population accounts for 80% of world’s resource consumption Poorest 20% is responsible for only 1.3% of consumption Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.10 Preserving Endangered Species Q: What is the most effective way to protect the environment and prevent extinctions of species? A: Preservation of ecosystems and monitoring species before they are threatened Habitat restoration Captive propagation Sustaining genetic diversity Preserving keystone species Conserving ecosystems Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Habitat Restoration In many situations, habitat conservation is no longer an option Three programs for restoration, depending on the cause of the habitat loss 1. Pristine restoration 2. Removing introduced species 3. Cleanup and rehabilitation Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Captive Propagation Recovery programs often involve direct intervention in natural populations to avoid extinctions Case History: The Peregrine Falcon Population disappeared east of the Mississippi by 1960 The culprit was DDT Causes eggs to break before they hatch DDT was banned by federal law in 1970 Captive breeding program started using falcons from other parts of the country Very good results Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Sustaining Genetic Diversity Smaller populations have little genetic diversity Case History: The Black Rhino All five species of rhinoceros are critically endangered Black rhinos live in 75 small, widely separated populations Diceros bicornis Fig. 34.17 To increase genetic diversity, individuals must be moved between populations Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Preserving Keystone Species Removal of keystone species can have disastrous consequences on ecosystems Pteropodid bat Case History: Flying Foxes Fig. 34.18 Widespread on the South Pacific Islands Often the only pollinator and seed disperser Were being driven to extinction by human hunting Legal protection, habitat restoration, and captive breeding have produced a very effective preservation program Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Conserving Ecosystems Isolated patches of habitat lose species far more rapidly than large areas do Conservation biologists have therefore promoted the following 1. The creation of megareserves Large areas of land that contain a core of one or more undisturbed habitats 2. The preservation of intact ecosystems Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 34.11 Individuals Can Make the Difference Two examples serve to illustrate this point The Nashua River in New England Lake Washington in Seattle Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Nashua River By the 1960s, was severely polluted by wastes from mills set up along its banks Marion Stoddart organized the Nashua River Cleanup Committee in 1962 Greatly aided passage of the Massachusetts Clean Water Act of 1966 Industrial dumping is now banned and the river has largely recovered Fig. 34.19 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Lake Washington By the 1950s, sewage dumping and fertilizer runoffs had caused a bloom of blue-green algae Bacteria decomposing dead algae would eventually deplete the lake’s oxygen In 1956, W.T. Edmondson of the University of Washington began a campaign to alert public officials of the danger A sewer was built to carry sewage effluent to the sea The lake is now clean Fig. 34.20 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Solving Environmental Problems Five components are involved in successfully solving an environmental problem 1. Assessment 2. Risk analysis 3. Public education 4. Political education 5. Follow-through Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display