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Scott Brennan • Jay Withgott 10 Biodiversity and conservation biology PowerPoint® Lecture prepared by Jay Withgott Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings This lecture will help you understand: • The scope of biodiversity on Earth • Extinction rates and mass extinction events • Causes of biodiversity loss • Benefits of biodiversity • Conservation biology • Island biogeography theory • Approaches to conservation Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Central Case: Saving the Siberian Tiger • Several types of tigers used to roam throughout Asia. • Some types are extinct; the Siberian tiger is endangered. • Conservation biologists have worked hard to save the tiger by educating people, preserving its habitat, and breeding them in zoos. Their efforts are now paying off. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings “Biodiversity” Biodiversity, or biological diversity = the sum of an area’s organisms, considering the diversity of species, their genes, their populations, and their communities There is no one exact definition of biodiversity; people have conceived of it in many ways. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Biodiversity’s foremost spokesman Biologist Edward O. Wilson has become the best-known spokesperson for biodiversity. An accomplished scientist and writer, he has raised awareness of threats to Earth’s life, and of impending species extinctions. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.1 Components of biodiversity Biodiversity exists on several levels: Genetic diversity Species diversity Ecosystem diversity Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.2 Species diversity The number or variety of species in a particular region Species richness = number of species Evenness, or relative abundance = extent to which numbers of different species are equal or skewed Species = a particular type of organism; a population or group of populations whose members share certain characteristics and can freely breed with one another and produce fertile offspring Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.2 Genetic diversity Includes the differences in DNA composition among individuals within a given species Adaptation to particular environmental conditions may weed out genetic variants that are not successful. But populations benefit from some genetic diversity, so as to avoid inbreeding or disease epidemics. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.2 Ecosystem diversity Includes diversity above the species level Biologists have viewed diversity above the species level in various ways. Some alternative ways to categorize it include: Community diversity Habitat diversity Landscape diversity Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.2 Species and taxonomy Each species is classified within a hierarchy reflecting the evolutionary diversification of life. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Two related species might be in the same genus; two related genera in the same family, etc. Figure 15.3 Diversity of subspecies Within species, diversity exists in subspecies, or geographic variations. The tiger, Panthera tigris, had 8 subspecies. 5 persist today, including Panthera tigris altaica, the Siberian tiger. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.4 Measuring biodiversity We are still profoundly ignorant of the number of species that live on our planet. Roughly 1.75 million species have been formally described by science. But many more exist: Estimates range from 3 million to 100 million. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Measuring biodiversity Why are we still so unsure of the number of species on Earth? • Some areas remain little explored (hydrothermal vents, rainforest canopies, tropical soils). • Many species are tiny and inconspicuous (microbes, roundworms, protists, fungi…). • Some species are very similar in appearance (many taxa, even trees, birds, whales). Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Distribution of biodiversity Species are not evenly spread among different groups. Insects comprise more than half of all species in world. Beetles comprise fully 40% of all insects. Mammals are outnumbered by spiders and their relatives 16 to 1. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Distribution of biodiversity Size of each organism is scaled to its number of species. Mammals are located in front of the insect’s mandibles. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.5a Distribution of biodiversity Some groups that have more species may have gone through an adaptive radiation. This is when an ancestral species give rise to many species that fill different niches, adapting to them by natural selection. Darwin’s Galápagos finches Hawaiian honeycreepers Asteraceae—daises and relatives Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Distribution of biodiversity Another pattern in the uneven distribution of biodiversity is the latitudinal gradient: species richness increases toward the equator. 30–100 bird species in large area of the Arctic 500–700 bird species in small area of the tropics Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.6 Latitudinal gradient Ecologists are not certain why the latitudinal gradient exists, but one prevalent idea is that tropical climates encourage specialist species that can pack tightly in a community. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.7 Biodiversity loss and species extinction Extinction = last member of a species dies and the species vanishes forever from Earth Extirpation = disappearance of a particular population, but not the entire species globally These are natural processes. On average one species goes extinct naturally every 500–1,000 years—this is the background rate of extinction. 99% of all species that ever lived are now extinct. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Mass extinctions Earth has experienced five mass extinction events in which over half its species were wiped out suddenly. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.8 Today’s mass extinction Currently Earth is undergoing its sixth mass extinction— because of us. Humans have increased the extinction rate by a factor of 1,000. 1,100 species are known to have gone extinct in the past 400 years. The Red List, from the IUCN, lists species that today are facing high risks of extinction. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Today’s mass extinction Species of large mammals and birds plummeted with the arrival of humans, independently, on each of three continents— suggesting that human hunting was the cause. Figure 15.9 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Causes of species extinction Primary causes spell “HIPPO”: • Habitat alteration • Invasive species • Pollution • Population growth • Overexploitation Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings “HIPPO”: Habitat alteration The greatest cause of extinction today Accounts for 85% of population declines of birds and mammals Habitat change hurts most organisms because they are adapted to an existing habitat. Alteration due to: Forest clearing Urban development Agriculture Global climate change Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings etc…. “HIPPO”: Invasive species Accidental or intentional introduction of exotic species to new areas Most do not establish or expand, but some do—likely because they are “released” from limitations imposed by their native predators, parasites, and competitors. In today’s globalizing world, invasive species have become perhaps the secondworst threat to native biota. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings “HIPPO”: Invasive species Examples: • Mosquito fish • Zebra mussel • Kudzu • Asian longhorned beetle • Rosy wolfsnail • Cane toad • Bullfrog Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings • Gypsy moth • European starling • Indian mongoose • Caulerpa algae • Cheatgrass • Brown tree snake Figure 15.10 “HIPPO”: Pollution Air and water pollution; agricultural runoff, industrial chemicals, etc. Pollution does serious and widespread harm, but is not as threatening as the other elements of HIPPO. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings “HIPPO”: Population growth Human population growth exacerbates every other environmental problem. Magnifies effects of the other elements of HIPPO: More people means more habitat change, more invasive species, more pollution, more overexploitation. Along with increased resource consumption, it is the ultimate reason behind proximate threats to biodiversity. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings “HIPPO”: Overexploitation Two meanings: Overharvesting of species from the wild (too much hunting, fishing…) Overconsumption of resources (too much timber cutting, fossil fuel use…) Usually overexploitation is not the sole cause of extinction, but it often contributes in tandem with other causes. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Causes of species extinction In most cases, extinctions occur because of a combination of factors. e.g., current global amphibian declines are thought due to a complex combination of: • Chemical contamination • Disease transmission • Habitat loss • Ozone depletion and UV penetrance • Climate change • Synergistic interaction of these factors Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Benefits of biodiversity Preserving biodiversity preserves ecosystem services, and directly provides things of pragmatic value to us. • Food, fuel, and fiber • Shelter and building materials • Air and water purification • Waste decomposition • Climate stabilization and moderation • Nutrient cycling • Soil fertility • Pollination • Pest control • Genetic resources Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Benefits of biodiversity: Food security Many species not now commonly used for food could be. Genetic diversity within crop species and their relatives enhances our agriculture and provides insurance against losses of prevalent strains of staple crops. Figure 15.11 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Benefits of biodiversity: Medicine Many species can provide novel medicines; we don’t want to drive these extinct without ever discovering their uses. Ten of our top 25 drugs come directly from wild plants; the rest we developed because of studying the chemistry of wild species. Figure 15.12 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Benefits of biodiversity: Economic benefits For all nations, ecotourism can be a major contributor to the economy—especially for developing nations rich in biodiversity. Affluent tourists pay good money to see wildlife, novel natural communities, and protected ecosystems. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Benefits of biodiversity: “Biophilia” Biophilia = human love for and attachment to other living things; “the connections that human beings subconsciously seek out with the rest of life” e.g., Affinity for parks and wildlife Keeping of pets Valuing real estate with landscape views Interest in escaping cities to go hiking, birding, fishing, hunting, backpacking… Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conservation biology Scientific discipline devoted to understanding the factors, forces, and processes that influence the loss, protection, and restoration of biological diversity within and among ecosystems. Applied and goal-oriented: Conservation biologists intend to prevent extinction. This discipline arose in recent decades as biologists grew alarmed at the degradation of natural systems they had spent their lives studying. Figure 15.13 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Equilibrium theory of island biogeography Explains how species diversity patterns arise on islands, as a result of: • Immigration • Extinction • Island size • Distance from the mainland The theory originally developed as basic science for oceanic islands. Then it was found to apply to islands of habitat (fragments) within terrestrial systems, for conservation biology. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Species-area curves The prediction of an increase in species with increased area of an island is borne out by data from nature. Here, species richness on islands of the Caribbean. Figure 15.15 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Testing island biogeography theory The theory was first tested experimentally on small mangrove islands in the Florida Keys. All arthropods were extinguished from them with a pesticide, and then the researchers observed as species returned to the islands. Equilibrium numbers matched their predictions, supporting the theory. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings From The Science behind the Stories Island biogeography theory in conservation The theory’s applicability to conservation became clear when a researcher documented historical declines in mammals in national parks. The extinctions matched predictions of the theory if the parks were thought of as islands. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings From The Science behind the Stories Fragmentation “Islands” of interest to conservation biologists include forest fragments. Forest fragmentation occurs as continuous forest habitat gets broken up gradually. This leads to local extirpations of forest species, as fragments become too small to support them, and too distant to allow immigration. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conservation approaches: Umbrella species When habitat is preserved to meet the needs of an “umbrella species,” it helps preserve habitat for many other species. (Thus, primary species serve as an “umbrella” for others.) Large species with large home ranges (like tigers and other top predators) are good umbrella species. So are charismatic ones that win public affection, like the panda. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conservation approaches: Endangered species Trying to preserve single species threatened with extinction is the goal of endangered species laws, although they often also achieve umbrella conservation. U.S. Endangered Species Act, 1973: • Restricts actions that would destroy endangered species or their habitats • Forbids trade in products from species • Prevents extinction, stabilizes and recovers populations Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conservation approaches: Endangered species The ESA has had notable successes: Bald eagle Peregrine falcon 40% of all declining populations held stable However, there is much popular resentment against the ESA: Many citizens believe it will restrict their freedom if endangered species are found on their land. Canada therefore stressed cooperation with landowners and provincial governments in its recent Species at Risk Act. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conservation approaches: Captive breeding Many endangered species are being bred in zoos, to boost populations and reintroduce them into the wild. This has worked so far for the California condor (in photo, condor hand puppet feeds chick so it imprints on birds, not humans). But this is worthless if there is not adequate habitat left in the wild. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15.17 Conservation approaches: Cloning A newly suggested approach is to use molecular techniques to clone endangered or even extinct species, raise them in zoos, and reintroduce them to the wild. Even if this succeeds technically, though, it will be worthless if there is not adequate habitat and protection left for them in the wild. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conservation approaches: International treaties Various treaties have helped conserve biota. A major one is CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, prepared in 1973. It bans international trade and transport of body parts of endangered organisms. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conservation approaches: International treaties The Convention on Biological Diversity (CBD), from the Rio Conference in 1992, aims to: • Conserve biodiversity • Use it sustainably • Ensure fair distribution of its benefits The CBD has been signed by 188 nations, but not by the United States. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conservation approaches: Biodiversity hotspots Biodiversity hotspot = an area that supports an especially high number of species endemic to the area, found nowhere else in the world Endangered golden lion tamarin, endemic to Brazil’s Atlantic rainforest, which has been almost totally destroyed Figure 15.18 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conservation approaches: Biodiversity hotspots Global map of biodiversity hotspots, as determined by Conservation International Figure 15.19 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Viewpoints: Biodiversity Norman Myers “If we could safeguard biodiversity hotspots, we could reduce the number of extinct species by at least one-third. However, global warming will shift temperature bands and vegetation communities, so these areas would still be vulnerable.” Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Peter Kareiva “Parks are a valuable strategy for conservation, but they are not the most important strategy. Conservation cannot just be about setting aside nature in parks but rather must address working landscapes and human use of biological resources.” From Viewpoints Conclusions: Challenges We still have little idea of how many species inhabit our planet. We have set the sixth mass extinction in motion. Population declines, extirpations, and extinctions result from habitat alteration, invasive species, pollution, population growth, and overexploitation. Fragmentation of habitats causes loss of species from habitat islands. Conservation biology is fighting an uphill battle to save species, habitats, and ecosystems. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conclusions: Solutions Biologists are making strides in determining how many species inhabit our planet. There is still time to halt the sixth mass extinction. We have ways to minimize habitat alteration, invasive species, pollution, and overexploitation, but success will ultimately depend on halting human population growth. Fragmented habitats can be restored, but preserving areas before they are fragmented is best to avoid species loss. Conservation biology has developed numerous and varied ways to save species, habitats, and ecosystems. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review Which of these pairs of terms is included in the acronym “HIPPO” that describes causes of biodiversity loss? a. Pollution and Indicator species b. Harvesting and Population decline c. Habitat alteration and Invasive species d. Overexploitation and Pollination e. Indicator species and Population growth Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review Which is NOT a benefit of biodiversity to humans? a. Economic benefits through ecotourism b. New potential sources of food c. New potential sources of drugs d. Ecosystem services e. All of the above are benefits of biodiversity. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review Which has NOT been an approach of conservation biologists? a. Identifying and mapping areas with large numbers of endemic species. b. Applying island biogeography theory to habitat fragments. c. Breeding animals in captivity. d. Requiring landowners to give up their land. e. Working with local communities to get them invested in conservation. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Weighing the Issues When North American pharmaceutical companies go “bioprospecting” in developing countries for compounds for new drugs and medicines, should they be required to pay the host country for its biodiversity? a. Yes; the biodiversity is a natural resource of the host country, and it should be paid a fee up front. b. Yes; the biodiversity is a natural resource of the host country, and it should share in any eventual profits from any medicines developed. c. No; the company is the one doing all the work, so all profits should go to the company. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Viewpoints Are parks and protected areas the best strategy for protecting biodiversity? a. Yes; it is absolutely necessary to preserve untrammeled habitat for species to persist. b. No; parks won’t matter because climate change will force the biota out of them. c. No; it is more effective to work with local people and give them economic incentives to conserve nature. Both parks and other strategies are necessary. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings