The anthropocene mass extinction: an emerging curriculum theme for science educators.
Curriculum planning (Management)
Mass extinction theory (Educational aspects)
|Publication:||Name: The American Biology Teacher Publisher: National Association of Biology Teachers Audience: Academic; Professional Format: Magazine/Journal Subject: Biological sciences; Education Copyright: COPYRIGHT 2011 National Association of Biology Teachers ISSN: 0002-7685|
|Issue:||Date: Feb, 2011 Source Volume: 73 Source Issue: 2|
|Topic:||Event Code: 200 Management dynamics Computer Subject: Company business management|
|Geographic:||Geographic Scope: United States Geographic Code: 1USA United States|
There have been five past great mass extinctions during the history of Earth. There is an ever-growing consensus within the scientific community that we have entered a sixth mass extinction. Human activities art" associated directly or indirectly with nearly every aspect of this extinction. This article presents an overview of the five past great mass extinctions; an overview of the current Anthropocene mass extinction; past and present human activities associated with the current Anthropocene mass extinction; current and future rates of species extinction; and broad science-curriculum topics associated with the current Anthropocene mass extinction that can be used by science educators. These broad topics are organized around the major global, anthropogenic direct drivers of habitat modification, fragmentation, and destruction; overexploitation of species; the spread of invasive species and genes; pollution; and climate change.
KeyWords: Biology curriculum; Anthropocene; extinction; anthropogenic; evolution.
* An Overview of Earth's Five Past Great Mass Extinctions
There have been five past great mass extinctions during the history of Earth (Jablonski, 1995; Erwin, 2001; see Figure 1). All five were characterized by "a profound loss of biodiversity during a relatively short period" (Wake & Vredenburg, 2008: p. 11466). The first mass extinction, the Ordovician-Silurian, occurred approximately (=) 439 million years ago (mya). The fifth, the Cretaceous-Tertiary, occurred [approximately equal to] 65 mya (Jablonski, 1995; Erwin, 2001). It was this extinction that saw the demise of the nonavian dinosaurs (Wake & Vredenburg, 2008). The most devastating mass extinction was the Permian-Triassic extinction ([approximately equal to] 251 mya), in which [approximately equal to] 95% of all global species went extinct (Jablonski, 1995; Erwin, 2001).
* An Overview of the Current Anthropocene Mass Extinction
There is an eve>growing consensus within the scientific community that we have entered a sixth mass extinction (McDaniel & Borton, 2002; Thomas et al., 2004; Lewis, 2006; Steffen et al., 2007; Alroy, 2008; Jackson, 2008; Rohr et al., 2008; Wake & Vredenburg, 2008; Rockstrom et al., 2009; Zalasiewicz et al., 2010). As Jeremy Jackson, director of the Center for Marine Biodiversity and Conservation and both the William E. and Mary B. Ritter Professor of Oceanography at the Scripps Institution of Oceanography and a senior scientist at the Smithsonian Tropical Research institute, has written:
The great mass extinctions of the fossil record were a major creative force that provided entirely new kinds of opportunities for the subsequent explosive evolution and diversification of surviving clades. Today, the synergistic effects of human impacts are laying the groundwork for a comparably great Anthropocene mass extinction ... with unknown ecological and evolutionary consequences. (Jackson, 2008: p. 11458)
In 2000, Paul Crutzen and Eugene Stoermer proposed that a new geological epoch had begun. They named the epoch the Anthropocene (pronounced an-thruh-po-seen) based on the "impact of human activities on earth and atmosphere" (Crutzen & Stoermer, 2000: p. 17). They stated that this geological epoch had begun in the "latter part of the 18th century" because by then "the global effects of human activities have become clearly noticeable" (Crutzen & Stoermer, 2000: p. 17). After this article and others (e.g., Crutzen, 2002; Crutzen & Steffen, 2003), the term "Anthropocene" entered the scientific lit erature informally (e.g., Steffen et al., 2004; Andersson et al., 2005; Crossland et al., 2005; Syvitski et al., 2005).
The Stratigraphy Commission of the Geological Society of London, by a large majority, decided in 2008 "that there was merit in considering the possible formalization of this term: that is, that it might eventually join the Cambrian, Jurassic, Pleistocene, and other such units on the Geological Time Scale" (Zalasiewicz et al., 2010: p. 2228). (1) These 21 scientists from across the scientific community stated that "sufficient evidence has emerged" (Zalasiewicz et al., 2008: p. 7) for a new geological epoch named the Anthropocene (Crutzen & Stoermer, 2000; Crutzen, 2002) in reference to "the contemporary global environment dominated by human activity" (Zalasiewicz et al., 2008: p. 4). These human activities, which form the basis for the proposed ongoing Anthropocene epoch, are also the very activities that are driving the current mass extinction. Ultimately, the current Anthropocene epoch and the current mass extinction are interconnected and indivisibly united by the environmentally degrading human activities of the past 200 to 300 years.
* Past & Present Human Activities Associated with the Current Anthropocene Mass Extinction
As Wake and Vredenburg (2008) wrote, "Human activities are associated directly or indirectly with nearly every aspect of the current extinction spasm" (p. 11472). These activities have taken many forms (see Figure 2). The most devastating and far-reaching anthropogenic direct drivers that are affecting global biodiversity are habitat modification, fragmentation, and destruction; overexploitation of species; the spread of invasive species and genes; pollution; and climate change (Millennium Ecosystem Assessment [MEAl, 2005; World Wide Fund for Nature [WWF], 2008). Humans use between a third and half of all land on Earth and move more soil, rock, and sediment than all natural processes combined (Lewis, 2006). Humans have constructed reservoirs that hold three to six times as much water as are contained in natural rivers (Lewis, 2006) and use more than half of all accessible fresh water (Crutzen, 2002).
Through burning of fossil fuels, humans have elevated atmospheric C[O.sub.2] concentrations to their highest levels in 15 million years, driving global warming, rising sea levels, and climate change (Tripati et al., 2009). Global fossil fuel emissions increased 29% from 2000 to 2008 and 41% from 1990 to 2008. The 29% increase from 2000 to 2008 occurred "m conjunction with increased contributions from emerging economies, from the production and international trade of goods and services, and from the use of coal as a fuel source" (Le Quere et al., 2009: p. 1).
At present, there are [approximately equal to] 6.8 billion humans on Earth. This number has increased tenfold in the past 300 years, fourfold in the past 100 years, and rough estimates place the global human population at 9 billion by 2040. Globally, [approximately equal to] 150 humans are born every minute. The global human "ecological footprint" exceeded Earth's biocapacity in the mid-to-late 1980s (WWF, 2008). Humans have become, through their sheer numbers and consumption rates, the greatest geophysical (Lewis, 2006) and evolutionary force on Earth (Palumbi, 2001).
* Current & Future Rates of Species Extinction
The impact of human activities has greatly affected global biodiversity. There are between 5 million and 30 million extant species on Earth (Dirzo & Raven, 2003; MEA, 2005). Over the past 200 to 300 years, humans have accelerated global species extinction rates 100-1,000 times Earth's historical geological background rate (Pimm et al., 1995; Mace, et al., 2005; Rockstrom et al., 2009), and modeled future extinction rates are projected to be 10,000 times the background rate (MEA, 2005).
Currently, 32% of amphibians, 23% of mammals, 12% of birds, 25% of conifers, and 52% of cycads (a group of evergreen palm-like plants) are threatened with extinction (MEA, 2005). These approximate percentages are known only because these five groups are the only major taxonomic groups that have been comprehensively assessed as of 2004 (MEA, 2005). Twenty percent "of known coral reefs have been destroyed and another 20% degraded in the last several decades" (MEA, 2005). As of 2008, there were an estimated 1,642,189 described species worldwide, only 44,838 of which had been assessed in terms of conservation status by the International Union for Conservation of Nature (IUCN) Red List. Of the 44,838 species on the 2008 IUCN Red List, over one-third (i.e., 16,928 species) were threatened with extinction (IUCN, 2009).
Further evidence comes from the Living Planet Index (WWE 2008). The Living Planet Index is a measurement of global biodiversity. It is based on the trends of nearly 5,000 populations of 1,686 species of mammals, birds, reptiles, amphibians, and fish throughout Earth. Using this index, a 30% decline in biodiversity has been observed from 1970 to 2005 (WWE 2008).
Approximately two-thirds of all organisms occur in the tropics, mainly in tropical humid forests (Pimm & Raven, 2000). More than half of the tropical humid forests on Earth have been destroyed. At current deforestation rates, it is estimated that the remaining tropical humid forests and the species they contain will be destroyed by 2060. If this were to occur, the extinction rate in these forests by 2060 would be [approximately equal to] 48,000 extinctions per million species per decade (Pimm & Raven, 2000). McDaniel and Borton (2002) stated that human industrial societies have monopolized Earth's biological energy flow and that when the current global modern societies' use of the planet's biological energy is compared with past hunter-gatherer societies, "the current mass extinction appears as a predictable, expected result" (p. 929).
* Education: A Mechanism of Reducing Global Environmental Degradation?
One component of possibly reducing the rising anthropogenic affects associated with the current Anthropocene mass extinction is education. The current Anthropocene mass extinction constitutes a newly emerging scientific theme that has great potential in science education. Because the current Anthropocene mass extinction has components related to life science and physical science, it offers many opportunities for integration across multiple disciplines (e.g., biology, chemistry, geology, and meteorology), multiple science courses, and other nonscience courses (e.g., social studies and mathematics) (National Research Council [NRC], 1996: p. 214 [see third paragraph and Program Standard C]). The theme also allows for implementation of scientific inquiry activities (NRC, 1996: p. 214 [see second paragraph]) in both formal educational settings (e.g., indoor and outdoor classrooms) and informal educational settings (e.g., nature centers and zoos) (NRC, 2009). Lastly, the theme is relevant to all students because in the future, on some level, it will affect their own quality of life and the well-being of other organisms (NRC, 1996: p. 212 [see Program Standard B]).
* Broad Science-Curriculum Topics Associated with the Current Anthropocene Mass Extinction
Because of these unique characteristics, the current Anthropocene mass extinction offers an abundance of educational opportunities for science educators. The major global anthropogenic direct drivers of biodiversity loss associated with the current Anthropocene mass extinction provide an excellent organizational framework for presenting the complexity and human challenges of this mass extinction. Figure 3 presents these direct drivers. Under each direct driver, broad science-curriculum topics are presented that can be used by science educators. Topics can be combined to integrate across drivers and across both physical and life-science disciplines. For all of the drivers, the scale of human impact can be addressed at the ecosystem, biome, or biosphere level. When a topic is used, it should be combined with topics and examples that address humanity's ability to ethically reduce the current trajectory of local, regional, and global environmental degradation. These topics include but are not limited to reduction of human consumption rates (i.e., per capita natural resources and ecological services) in developed countries; reduction in global human population growth; and development and implementation of environmentally sustainable human activities.
Clearly, the greatest challenge facing humanity is stopping the destruction of the very biosphere that sustains us. The current Anthropocene mass extinction provides an emerging, integrative, inquiry-based, and relevant theme for educating students about global environmental degradation and how it might be reduced. Ultimately, educating students about the current Anthropocene mass extinction is key to giving them the knowledge and skills necessary to be scientifically literate citizens (Rutherford & Ahlgren, 1990; American Association for the Advancement of Science, 1993) who can fully participate in this, humanity's greatest challenge.
DOI: 10.1525/a bt.2011.73.2.5
References & Further Reading
Note: An asterisk indicates that the document is free online and can be incorporated into middle school, high school, and college science courses.
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(1) Presently, the term "Anthropocene" remains informal. "The first (of many) formal steps are now being taken. An Anthropocene Working Group has been initiated, as part of the Subcommission on Quaternary Stratigraphy (the body that deals with formal units of the current Ice Ages). That is itself part of the International Commission on Stratigraphy, in turn answerable to the International Union of Geological Sciences" (Zalasiewicz et al., 2010: p. 2228; for more information on this subject, see that publication).
RON WAGLER is Assistant Professor of Science Education at the University of Texas at El Paso, 500 West University Avenue, Education Building 601, El Paso, TX 799680571; e-mail: email@example.com.
Figure 1. An overview of Earth's five past great mass extinctions. The evolution of life on Earth has been greatly influenced by mass extinctions. After all five past mass extinctions, recovery was facilitated by the evolution of new species instead of the reexpansion of the survivors. Ordovician-Silurian Extinction ([approximately equal to] 439 mya) Cause of Extinction: "Great fluctuations in sea level, which resulted from extensive glaciations, followed by a period of great global warming." Loss of Global Biodiversity: "Approximate 25% of the families and nearly 60% of the genera of marine organisms were lost." Late Devonian Extinction ([approximately equal to] 364 mya) Cause of Extinction: "Global cooling after bolide impacts may have been responsible because warm water taxa were most strongly affected." Loss of Global Biodiversity: "22% of marine families and 57% of marine genera, including nearly all jawless fishes, disappeared." Permian-Triassic Extinction ([approximately equal to] 251 mya) Cause of Extinction: "Causes are debated, but the leading candidate is flood volcanism emanating from the Siberian Traps, which led to profound climate change. Volcanism may have been initiated by a bolide impact, which led to loss of oxygen in the sea. The atmosphere at that time was severely hypoxic, which likely acted synergistically with other factors." Loss of Global Biodiversity: "95% of all species (marine as well as terrestrial) were lost, including 53% of marine families, 84% of marine genera, and 70% of land plants, insects, and vertebrates." End Triassic Extinction ([approximately equal to] 199-214 mya) Cause of Extinction: "Opening of the Atlantic Ocean by sea floor spreading related to massive lava floods that caused significant global warming." Loss of Global Biodiversity: "Marine organisms were most strongly affected (22% of marine families and 53% of marine genera were lost), but terrestrial organisms also experienced much extinction." Cretaceous-Tertiary Extinction ([approximately equal to] 65 mya) Cause of Extinction: "Causes continue to be debated. Leading candidates include diverse climatic changes (e.g., temperature increases in deep seas) resulting from volcanic floods in India (Deccan Traps) and consequences of a giant asteroid impact in the Gulf of Mexico." Loss of Global Biodiversity: "16% of families, 47% of genera of marine organisms, and 18% of vertebrate families were lost." Note: Direct quotations are from Wake and Vredenburg (2008: p. 11466). Wake and Vredenburg's original sources were Erwin (2001) and Jablonski (1995).
Figure 2. Past and present human activities associated with the current Anthropocene mass extinction. * "Water withdrawals from rivers and lakes doubled since 1960; most water use (70% worldwide) is for agriculture." (MEA, 2005: p. 2) * "Fisheries remove more than 25% of the primary production in upwelling ocean regions and 35% in the temperate continental shelf." (Crutzen, 2002: p. 23) * "Humanity's demand on the planet's living resources, its ecological footprint, now exceeds the planet's regenerative capacity by about 30 percent. This global overshoot is growing and, as a consequence, ecosystems are being run down and waste is accumulating in the air, land and water." (WWF, 2008: p. 2) * "Energy use has grown 16-fold during the twentieth century, causing 160 million tonnes of atmospheric sulphur dioxide emissions per year, more than twice the sum of its natural emissions." (Crutzen, 2002: p. 23) * "Global economic activity increased nearly sevenfold between 1950 and 2000." (MEA, 2005: p. 64) * "More nitrogen fertilizer is applied in agriculture than is fixed naturally in all terrestrial ecosystems." (Crutzen, 2002: p. 23) * "Humans have caused a dramatic increase in erosion and the denudation of the continents, both directly, through agriculture and construction, and indirectly, by damming most major rivers, that now exceeds natural sediment production by an order of magnitude (Syvitski et al., 2005; Wilkinson, 2005)." (Zalasiewicz et al., 2008: p. 5) * "Nitric oxide production by the burning of fossil fuel and biomass also overrides natural emissions." (Crutzen, 2002: p. 23)
Figure 3. Broad science-curriculum topics associated with the current Anthropocene mass extinction. Major anthropogenic direct driver of biodiversity loss: Habitat modification, fragmentation, & destruction Example Science Curriculum Topics * Acid rain's impact on habitat loss * Effects of global warming on habitat (e.g., polar ice cap reduction and sea level rising) * Deforestation rates and locations * Effects on invertebrate biodiversity (e.g., corals, insects, crustaceans, and arachnids) because of habitat modification, fragmentation, and destruction * Examples of habitat modification, fragmentation, and destruction (e.g., Madagascar and North American tallgrass prairie) * Impact on a species' evolution (e.g., reduced gene flow and genetic drift) because of habitat modification, fragmentation, and destruction * Impact on endangered and threatened species because of habitat modification, fragmentation, and destruction * Association between human population dynamics (e.g., population growth, population density, factors that affect and regulate population growth) and habitat modification, fragmentation, and destruction * Impact on global carrying capacity because of habitat modification, fragmentation, and destruction * Impact on trophic levels, food chains, food webs, and energy flow within ecosystems because of habitat modification, fragmentation, and destruction * Past and current species extinctions associated with habitat modification, fragmentation, and destruction * Physical alteration of waterways and its impact on habitat * Role of habitat modification, fragmentation, and destruction in species extinction * Impact of habitat modification, fragmentation, and destruction on erosion and sedimentation rates * Impact of habitat modification, fragmentation, and destruction on natural cycles (e.g., rock) Major anthropogenic direct driver of biodiversity loss: Overexploitation of species Example Science Curriculum Topics * Examples of overexploitation of species (e.g., American bison and Galapagos tortoise) * Impact on a species evolution because of overexploitation (e.g., reduced fitness and reduced gene pool variability) * Impact of overexploitation of species on endemic, endangered, and threatened species * How the goal of environmental sustainability is affected by overexploitation of species * Effects of overexploitation of species on vertebrate biodiversity (e.g., fish, amphibians, reptiles, bird, and mammals) * Association between human population dynamics (e.g., population growth, population density, factors that affect and regulate population growth) and overexploitation of species * Examples of species extinctions because of overexploitation * Overexploitation of species and its impact on predator-prey cycles * Overexploitation of species and its impact on trophic levels, food chains, food webs, and energy flow within ecosystems * Overexploitation of species role in species extinction * Overexploitation of tropical humid forests and other forests * Past and present species extinctions associated with overexploitation of species Major anthropogenic direct driver of biodiversity loss: The spread of invasive species & genes Example Science Curriculum Topics * Effect of global warming (e.g., increased range of invasive species) * Examples of invasive species (e.g., Guam [brown tree snake] and Australia [cane toad]) * Impact of invasive species on endemic, endangered, and threatened species * Impact of invasive species on noninvasive species' evolution (e.g., natural selection) and coevolution * Impact of invasive species on predator-prey cycles * Impact of invasive species on trophic levels, food chains, food webs, and energy flow within ecosystems * How the goal of environmental sustainability is affected by the spread of invasive species and genes * Invasive species' role in species extinction * Influence of invasive species and genes on biodiversity, biocapacity, species richness, genetic diversity, and ecosystem diversity Major anthropogenic direct driver of biodiversity loss: Pollution Example Science Curriculum Topics * Acid rain * Air pollutants (e.g., carbon monoxide, nitrogen dioxide, sulfur dioxide, lead, [PM.sub.2.5], and [PM.sub.10]) * Pollution's impact on natural cycles (e.g., carbon, nitrogen, sulfur, and phosphorus) * Bioaccumulation and biomagnification of chemicals (e.g., mercury and PCBs) in food chains * Chlorofluorocarbon (CFC) and stratospheric ozone depletion (i.e., the ozone hole) * Eutrophication and anoxia * Association between per capita human ecological/carbon footprint and pollution * Association between human population dynamics (e.g., population growth, population density, factors that affect and regulate population growth) and pollution * Soil pollutants (e.g., hydrocarbons, heavy metals, herbicides, and pesticides) * Bioindicators (e.g., amphibians) as a way to determine pollution's impact on ecosystems * Mercury deposition * Pollution's impact on a species' evolution (e.g., mutation) * Pollution's impact on human health * Pollution's impact on predator-prey cycles * Pollution's impact on trophic levels, food chains, food webs, and energy flow within ecosystems * U.S. superfund sites * Water pollutants (e.g., volatile organic compounds and fertilizers) Major anthropogenic direct driver of biodiversity loss: Climate change Example Science Curriculum Topics * Effect of global warming (e.g., change in precipitation patterns and problems for agriculture) * Climate change's impact on predator-prey cycles * Association between per capita human ecological/carbon footprint and climate change * Deforestation's role in climate change * Consequences of climate change on producers, consumers, and decomposers * Role of greenhouse gases (e.g., carbon dioxide, methane, surface ozone, and nitrous oxide) in climate change * Relationship between atmospheric carbon dioxide and ocean acidification * Ocean acidification's impact on organisms * Effects of climate change on plant biodiversity * Impact of climate change on trophic levels, food chains, food webs and energy flow within ecosystems * Increased desertification as a result of climate change * Alteration of natural cycles (e.g., water) because of climate change * Role of climate change in species' extinction
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