HUMAN IMPACTS ON THE BIOSPHERE

48 Human Impacts on the Biosphere Chapter Outline A Long Reach The Extinction Crisis Mass Extinction The Sixth Great Mass Extinction Currently Threatened Species Causes of Species Declines The Unknown Losses HARMFUL LAND USE PRACTICES Desertification Deforestation TOXIC POLLUTANTS Acid Rain Biological Accumulation and Magnification The Trouble with Trash OZONE DEPLETION AND POLLUTION Depletion of the Ozone Layer Near-Ground Ozone Pollution EFFECTS OF GLOBAL CLIMATE CHANGE CONSERVATION BIOLOGY The Value of Biodiversity Setting Priorities Preservation and Restoration REDUCING NEGATIVE IMPACTS A LONG REACH (REVISITED) SUMMARY DATA ANALYSIS EXERCISE SELF-QUIZ CRITICAL THINKING Objectives 1. Realize that there have been five mass extinctions that occurred naturally and we could be heading to an era of a manmade extinction. 2. Be able to describe how many species are endangered or threatened due to deforestation, desertification, hunting, and species introduction. 3. Know that we are aware of many threatened species, but there are probably many more than we think. 4. List the efforts made to protect habitats and regions at risk. 5. Know that many species are affected by our process of overdevelopment and over-use of non-renewable resources. 6. Realize that many grasslands are changing into deserts due to poor farming techniques that lead to soil erosion. 7. Understand that plastic trash and acid rain harm animal species. 8. Know that humans can positively impact organisms by appropriate farming and by educating the public at large about environmental issues. Key Terms mass extinction endangered species threatened species endemic species acid rain bioaccumulation biological magnification pollutant ozone layer biodiversity conservation biology ecological restoration genetic biodiversity species biodiversity ecosystem biodiversity indicator species hot spots ecoregions desertification riparian zones Lecture Outline 48.1 The Long Reach A. Far-reaching impacts of man are felt in areas like the North Pole. 1. Greenhouse gases are causing global warming, which melts polar ice caps. 2. Animals in arctic regions have high levels of mercury and other toxic substances. B. All areas of the world have evidence of human intervention. 1. Many animal and plant species are suffering the effects of man’s activities. 2. We now have the knowledge to understand man’s influence on the environment and to attempt to minimize it. 48.2 The Extinction Crisis A. Mass Extinction 1. Extinction is a natural process. a. Scientists estimate that 99 percent of all species that ever existed are extinct. 2. The Earth has already had five natural mass extinctions. a. The greatest mass extinction was at the end of the Permian era. 1) This extinction was caused by the consequences resulting from volcanic activity. b. Sometimes a decrease in the numbers of one species encourages expansion of another species. 1) For example, when the number of gymnosperms decreased, angiosperms became dominant. B. The Sixth Great Mass Extinction 1. A sixth mass extinction caused by man’s interference may be underway. 2. The arrival of humans coincided with the extinction of many large animals. a. Hunting animals contributed to the demise of many species. 3. Other causes of extinction are: climate variation, comet impacts, and diseases that are introduced by humans. Animals such as the dodo bird are extinct due to destruction of their habitat and hunting by man. 48.3 Currently Threatened Species A. An endangered species is one that is in immediate danger of extinction, whereas a threatened species is one that is likely to become endangered. B. Causes of Species Declines 1. One common cause of the decline of a species is overharvesting. a. This is the case in the Atlantic codfish population, and also with the invertebrate the white abalone. b. Scientists are using captive breeding techniques to attempt to rejuvenate the species. 2. Endemic species are most vulnerable because they live in a limited area. a. Panda bears are an example of an endemic species. 3. Destruction of their native habitat is a major reason why species become endangered. a. This affects plants (e.g., prairie fringed orchid) and animals (e.g., ivory-billed woodpecker). 4. Man has hindered natural habitats by introducing foreign species. a. Examples of predators that are interfering with natural environments are: rats, brown tree snakes, kudzu, and Japanese honeysuckle. 5. Often the decline in one population will lead to a decrease in another population. a. An example is the decrease of both bison and buffalo clover. 6. The use of biological controls can affect species other than the intended target. C. The Unknown Losses 1. A great number of species are either currently evaluated for threats or found to be threatened, as noted by the International Union for Conservation of Nature and Natural Resources. It is unknown how many other species, such as microbes or protists, are also endangered. 48.4 Harmful Land Use Practices A. Desertification 1. Grasslands can develop desert-like conditions in a process called desertification. a. This can be caused by over-grazing, improper farming, droughts, and heavy winds. b. An example can be seen in the Great Plains or in the Gobi desert. 2. The best method to avoid desertification is to restrict farming from areas with drought conditions and high winds. B. Deforestation 1. Deforestation destroys habitats, encourages flooding, and increases the chance of landslides. 2. This destruction of forests reduces the nutrient content of the soil and affects weather. 3. The most deforestation is occurring in Central and South America. 48.5 Toxic Pollutants A. Pollutants are defined as natural or man-made substances that are released into soil, air, or water in greater-than-natural amounts. B. Acid Rain 1. Acid rain is primarily caused by the emission of sulfur dioxides and nitrogen oxides into the air. a. These gases are released from coal-burning plants, cars, and power plants. 2. When these acidic gases combine with precipitation, it is called acid rain. 3. Acid rain harms aquatic organisms, trees, and plants. a. Acid rain disrupts nutrient cycles in the soil. C. Biological Accumulation and Magnification 1. Some plants can be used to help eliminate pollutants from the environment. 2. Animals tend to accumulate toxins in fatty tissues, so older animals show more effects. 3. The amount of toxins increase as you move up the food chain, so those animals exhibit biological magnification (increased levels of the pollutant). a. An example of biological magnification occurred when fish-eating birds accumulated a very large concentration of DDT. D. The Trouble with Trash 1. Plastic trash can kill organisms. a. Birds, fish, and other marine organisms are particularly affected by ingesting or becoming tangled in plastic. 2. Many plastic products do not biodegrade for decades or more. 48.6 Ozone Depletion and Pollution A. Depletion of the Ozone Layer 1. The ozone layer refers to the area about 10–17 miles above sea level that contains lots of ozone. a. This layer helps shield us from harmful UV radiation, which can cause mutations. b. Exposure to UV rays also increases the incidence of skin cancer. c. Plants are also affected by additional UV exposure. 2. In the 1970s, scientists noticed that the layer was becoming thinner, and a decade later it appeared so thin that it was referred to as the hole in the ozone. 3. Chlorofluorocarbons (CFCs) are the main culprit in the destruction of the ozone layer. a. In 1987, many nations agreed to phase-out the use of CFCs. b. Even though the CFCs are not being released in great amounts, they are still breaking down and impairing the ozone layer. B. Near-Ground Ozone Pollution 1. Ozone near the ground is considered a pollutant. a. This type of ozone is formed when organic compounds are burned or when exposed to sunlight. To reduce ozone as a pollutant, avoid any activities that release gas into the air where they will be exposed to direct sunlight. 48.7 Effects of Global Climate Change A. Average temperatures are increasing due to global warming. B. Climate changes have a huge impact on the environment. 1. The water level rises due to the rising temperature and glacial melting. 2. The salinity and acidity of the water is also affected. 3. Rainfall levels change. C. Many animal and plant species utilize temperature clues to know when to flower or reproduce. D. Humans may be more prone to infectious diseases and heat strokes. 48.8 Conservation Biology A. The Value of Biodiversity Biodiversity includes genetic diversity within a species, species diversity, and ecosystem diversity. Conservation biology serves to monitor biodiversity and find ways to protect it. Biological wealth includes benefits that can be derived from the environment. Some plant and animal products may produce valuable chemicals and medicines. Plants produce oxygen and use up carbon dioxide. Plants hold soil in place to prevent erosion. Other organisms decompose and detoxify wastes. Natural species can be combined with farm crops to produce an improved type of plant B. Setting Priorities 1. Conservation biologists chose the areas that need protection first, called hot spots. 2. Conservation biologists also defined 867 ecoregions and specified those that are the most in need of ecological efforts. C. Preservation and Restoration 1. A scientist studying the birds of Costa Rica purchased some of the land as a sanctuary. a. This encouraged others to donate land and money so the area flourishes. 2. Ecological restoration is the renewal of a severely damaged ecosystem. a. Restoration efforts are underway to improve conditions in the Louisiana marshlands. 48.9 Reducing Negative Impacts A. Helping society to understand sustainability is a major initiative today. 1. Supplies for newer, extravagant homes may damage the environment. a. For example, copper wiring must be mined and may create ecological dead zones in its wake. 2. The recycling of goods prevents the need for more extractions of materials from the environment. 3. Reduction of energy use, especially of fossil fuels, is a prudent practice. a. Walk, ride a bike, car pool, or take public transportation. 4. Consider carefully the impact of all renewable resources. 5. Support environmental causes through your votes and also with your wallet. 48.10 The Long Reach (Revisited) Ice sheets in the arctic are breaking up as a result of global warming. These melting conditions will make it easier to remove minerals and fossil fuels from the area. Since these materials are in short supply, pressure is mounting to excavate in this area. Conservationalists warn that these processes may destroy a valuable biome. Suggestions for Presenting the Material Now that we have completed the ecology section of the book, it may be time to review some of the past chapters. This chapter deals entirely with man’s interference, but some of the previous chapters deal with some of the concepts in more detail. Review concepts such as acid rain, crop rotation, greenhouse gases, and global warming before beginning the chapter. You may want the class to see the movie “An Inconvenient Truth,” which deals with many of the ecological concepts that we have discussed in this section of the book. The movie does a great job of visually representing statistics and views of the actual biomes. Start the discussion with some slides of animals in trouble due to man’s influence (e.g., a polar bear on a melting ice cap, a bird caught in plastic netting, etc). These types of powerful images may open up the discussions. Have each student write a short essay concentrating on the environmental issue from this chapter that really stood out in their minds. Use a “Jeopardy” or “Who Wants To Be a Millionaire” format to review the key terms from this chapter and the previous ecology chapters. A template for these games can be found at: _http://teach.fcps.net/trt2/links/powerpointgames.htm_ Design a questionnaire for students to use outside of your classroom. Each student in the class should poll 10 non-science-major students. Have the questionnaire ask a few simple questions relating to information from this course about air pollution. Your survey will be assessing the layperson’s knowledge of basic facts about pollution. Tabulate your results—where they what you expected? Keep in mind that the average college student may be better informed that an older individual with no formal environmental education. What can be done to heighten awareness about air pollution? Obtain a map of the United States showing the areas of highest cancer rates. Do you see any clusters of high cancer areas? Ask the students to speculate as to why certain areas are more at risk than others. Why does normal rainwater have a pH of around 5.6? Classroom and Laboratory Enrichment Assign each student an endangered or threatened species to investigate fully. What is the major reason for its decline? What could be done to save this species? Refer to http://_www.iucnredlist.org/_ for lists of endangered and threatened species. Look into the previous five mass extinctions. If the humans of today with their advanced technology had lived during any of these extinctions, do you think the extinctions would have been preventable? Research some animals that are extinct. Do you think the animal could have developed an adaptation that would have enabled it to survive? Take a field trip to a local zoo. Do the animals seem to be in their natural habitat? What changes could be made to mimic their native surroundings? Why do you think caged animals do not always reproduce successfully? Could anything be done to improve this? Research some extinct plants. Why couldn’t these plants be artificially maintained? When you observe the number of species on Table 48.1, the number of insect species really stands out. What features of insects make them so successful? Focus on one of the critical or vulnerable ecoregions in Figure 48.14. What circumstances have lead to the deterioration of these areas? Why are Americans the major users of all the resources of the world? What country do you think would rank second? Look into the events leading up to the Dust Bowl in the Great Plains. When did this take place? How could better farming methods have avoided this occurrence? How could we avoid the plastic trash from being consumed by marine animals? What can we do about this? Do you think by educating the public about the economic value of some biological products, we can do more to save ecosystems? How is strip logging superior to normal logging techniques? Interview the director of physical plants at your school. How does your school recycle products? Do you recycle glass, plastics, and paper? Are there recycling containers at prime locations throughout the campus? If not, how can this be improved? Invite an environmental speaker to your class from the EPA, state coastal commission, etc. Have each student prepare a question to ask this expert. Research federal laws regarding air pollution passed in the last 10 years. Do you think these laws are too lenient? What changes would you recommend? Divide the class into small groups and debate the pros and cons of different energy sources. Each section should be prepared to discuss the merits and drawbacks of one of the following energy sources: oil, coal, natural gas, hydropower, solar power, nuclear power, and other alternatives. Look at the website http://_www.epa.gov/superfund/_ to see if there are any superfund sites near your home or college. These sites are targeted by the EPA for clean up since they are considered to be uncontrolled hazardous waste sites. Classroom Discussion Ideas Scientists have begun to realize that events that occur in one part of our planet may have profound consequences for the entire planet and its inhabitants. Nowhere is this more evident than in the Arctic regions. Previously, man was only concerned with stripping all of the natural resources from this uninhabited area. No one noticed, or cared to notice, changes in the Arctic environment. Only in recent history has man really studied the loss of the polar ice caps and the effect this has on the rest of the Earth. The polar ice caps are melting due to global warming, which affects everyone on our planet. In most areas of the globe, an increase in temperature of a few degrees goes unnoticed, but when one looks at the effects this has on our polar environment, it is shocking! We need to find ways to extract oil and minerals from the Arctic without damaging their ecology. If this is not feasible, then perhaps we should abandon our mining of these substances to preserve the valuable ecosystem there. Let’s hope that we can find a way to study the Arctic habitat without damaging it further. Additional Ideas for Classroom Discussion Name some indicator species. What traits make these species able to signal adverse conditions in the environment? Choose one area of the country and plot the average yearly temperatures as far back as these statistics were measured. Does your graph show signs of global warming? Many grocery stores use the word “organic” to describe their products. Are there any laws defining the term? How about the term “green”? Is that term legally defined? Could some companies try to falsely market their products by saying they are environmentally friendly? Are there any steps you could personally take to decrease plastic trash, other than recycling? In Brazil, they utilize sugar cane as a common energy source. Why do we not use these methods in the United States? There is a very large island of trash that has accumulated in the Pacific Ocean. See if you can find out further information about this and how it is being addressed. Desertification is a natural process. In manmade deserts, a vicious cycle occurs. As the ground becomes dry, species die off. With less vegetation undergoing transpiration, the rain decreases. Look at events in a newly formed desert and see if this cyclic process has occurred. How do we determine which endangered species have the greatest value to the planet? Do animals always take precedence over plants? Should the animals that are not “warm and fuzzy” be given the same attention as those that we consider to be “cute”? When building a new home, what practices could you follow to make the house a “green” home? Are there any houses in your area that have adaptations that are environmentally friendly? Why is the ozone layer of the Earth’s atmosphere shrinking at the same time that excessive amounts of ozone at the Earth’s surface are present in photochemical smog? How many students in the class recycle their aluminum cans? Newspapers? Glass? Take a hand count. Ask students for reasons they do or do not recycle? Does your school collect recyclables? If not, could this be suggested at a student government meeting? What is low-sulfur coal? How is this better environmentally? What is thermal pollution? What are its effects? What nations are actively enacting laws against air pollution? Are they stricter or more lenient than those in the United States? How Would You Vote? Classroom Discussion Ideas Monitor the voting for the online question. Point out to the class that the environment at the poles is extremely unique. If it were to become damaged further, species may become extinct or at the very least endangered. If this environment is permanently destroyed, there is nowhere else on Earth that can support many of these species. Perhaps more emphasis should be place on renewable resources. What are some renewable resources that could replace petroleum? Why are they not currently being used? At some point, our energy needs will have to be supplied by renewable resources. Why not now, before we lose valuable ecosystems like that of the Arctic? The sixth mass extinction will be the first that is driven by man. What is our moral obligation to other species to prevent this? Have each student write a letter to their congressman or the CEO of a company to ask about environmentally friendly practices that are underway. Currently some of the species that live in the Arctic are endangered. The devastation produced by additional assaults on the area could mean the end for these organisms. In addition, we need to send the message to other countries that we highly value the diversity of nature and hope that they do the same. Term Paper Topics, Library Activities, and Special Projects Scientists have been boring into ice caps to test ice cores for environmental factors of the past. Recently they feel more pressured to complete this study. Why? By looking at past examples of major extinctions, about how long do you think it takes an environment to return to the previous level of diversity? Review a study done in New Jersey to see if pollution is harming the mosquito species. Although most people are not too concerned about the welfare of the mosquito, it can be used as an indicator species. What trait of a mosquito make it well-suited as an indicator species? Many parts of Florida have been particularly vulnerable to the introduction of non-indigenous species. Is this making southern Florida a threatened ecosystem? What can be done about this? Look in your daily paper or weekly news magazine for an article about an environmental issue. Summarize the article for the class. Do you see that defining areas for ecotourism is a mixed blessing? These areas are set aside to be protected, yet lots of tourists are passing through and possibly damaging the environment. Pick a particular area that is used for ecotourism and see if its human visitors have had an impact. Some individuals feel that all of the environmental problems we experience can be boiled down to one cause—overpopulation. How do you think the population explosion should be addressed? Would legislation like that in China work in the United States? Research malformations that have been widespread in amphibians recently. They have found other amphibians with malformed limbs, etc. Do you relate this to pollution? How can this be determined? Are frogs an indicator species in their environment? Research the case where some samples of Tylenol were poisoned. What permanent impact did this case have on our environment due to the creation of tamper-free products? How much did our plastic trash increase? Can we classify the Gulf Stream as an endangered ecosystem? Does it appear to be disappearing? Read a book about environmental topics and do a report for the class. Locate articles that discuss the deforestation of the rain forests. At what rate are they being destroyed? If deforestation continues at this rate, how long will it be before there are no more rain forests? Describe the actual contents of industrial smog or photochemical smog in the nearest city with an air pollution problem. Describe the ways in which the air pollution affects the health of area residents. Biological magnification of mercury may occur in humans that ingest large quantities of certain fish. Which fish are most likely to contain high mercury levels? Are these species restricted from the diets of pregnant women? What are the effects of acid rain on fish populations? Have a student choose one type of energy source. Is it renewable or non-renewable? Do you expect this type of production to increase or decrease over the next 25 years? Countries like India and China are major contributors to air pollution. Has there been any correlation between their increased air pollution levels and respiratory diseases? Some people say that China’s biggest export is air pollution. Do you agree with this statement? Why is the western United States the recipient of much of this pollution? Pick a species that is damaged by acid rain. How does the acid rain impact the lives of these organisms? Are there sustainability courses available at your institution? Suggest the significance of adding some environmentally friendly courses. Write a letter to a company that you feel uses excessive packaging. Do you have suggestions for how the packaging materials could be more environmentally friendly? Join or start an ecological club on campus. What should be your first project? Or start a “green club” at a local middle school. Have the students publish a newsletter with ecologically prudent ideas for improvements in their homes, their school, and their community. Possible Responses to Critical Thinking Questions As we know from this chapter and the previous ones, greenhouse gas emission causes global warming. In my area it is evident that many migratory birds are traveling further north due to the problem of increased temperatures. This requires that the birds establish new zones of habitat, and they may be displacing birds indigenous to that new locale. As you know, displacing one animal species may disrupt an entire food web. Also, if the average temperature rises significantly, animals may be subject to diseases that were previously only found in tropical locales. Plant species may also have difficulty adjusting to the new temperature range. As you can see, temperature changes could have a major impact on the species residing there. Often the amount of dangerous toxins in an animal’s body depends on their diet. If the organisms consumed by an animal, such as a ringed seal, contain the pollutants, then the toxin becomes biologically magnified in the larger animal. A bowhead whale consumes plankton, which would not retain the toxins as well as the marine animals that are the diet of the seal. 3. In any area, it seems as though the species that naturally lives in that environment should take precedence over an introduced species. People are obviously opposed to destroying the feral cats since they envision cats as friendly house pets. It would be best if feral cats were captured and neutered before their release. Hopefully this would decrease the feral cat population sufficiently to let the bird population recover adequately. Possible Responses to Data Analysis Exercise Questions Harmful chemicals travel to Arctic locations via wind, where they enter food webs. Through the process of biological magnification, the toxins enter the bodies of the Arctic people. This study was performed to see if the level of PCBs influences the sex of unborn children. More males were born to women with less than one microgram per milliliter of PCB in their serum. Women were more apt to have daughters when their PCB concentration was greater than 4.0 micrograms per milliliter. If a village had an inordinate amount of female newborns, one would expect the PCB levels to be above four micrograms per milliliter. 478 Chapter Forty-Eight 487 Human Impacts on the Biosphere 478 Chapter Forty-Eight 487 Human Impacts on the Biosphere 478 Chapter Forty-Eight 487 Human Impacts on the Biosphere 478 Chapter Forty-Eight 487 Human Impacts on the Biosphere 478 Chapter Forty-Eight 487 Human Impacts on the Biosphere 478 Chapter Forty-Eight 487 Human Impacts on the Biosphere