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Chapter 31 Conserving Earth’s Biodiversity Lectures by Gregory Ahearn University of North Florida Copyright © 2009 Pearson Education, Inc.. 31.1 What Is Conservation Biology? Conservation biology is the branch of science that seeks to understand and conserve biological diversity (biodiversity) and can be analyzed at different levels. • Genetic diversity is the variety and relative frequencies of different alleles in the gene pool of a species. • Species diversity is the variety and relative abundance of different species. • Ecological diversity is the variety of different ecosystems. Copyright © 2009 Pearson Education Inc. 31.1 What Is Conservation Biology? Conservation biologists study and seek to preserve biodiversity at all levels. • They apply methods drawn from ecology, genetics, and evolutionary biology to help protect and maintain the diversity of life. • If genetic diversity of a species is reduced, the species may lack the genetic variability to evolve adaptations to changing environments. • If the species diversity of an ecosystem is reduced, community interactions necessary to maintain an ecosystem may be threatened. Copyright © 2009 Pearson Education Inc. 31.1 What Is Conservation Biology? Conservation biologists study and seek to preserve biodiversity at all levels (continued). • If ecological diversity is reduced, the ability of the biosphere to support species may be compromised. • The knowledge gained by conservation biologists can help preserve biodiversity only if it is used to inform actions that prevent human-caused extinctions. Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Ecosystem services: practical uses for biodiversity • • • • • • • • Purifying air and water Replenishing atmospheric oxygen Pollinating plants and dispersing their seeds Providing wildlife habitat Decomposing wastes Limiting erosion and flooding Controlling pests Providing recreational opportunities Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Ecosystem services Ecosystem services Directly used substances • food plants and animals • building materials • fiber and fabric materials • fuel • medicinal plants • oxygen replenishment Indirect, beneficial services • maintaining soil fertility • pollination • seed dispersal • waste decomposition • regulation of local climate • flood control • erosion control • pollution control • pest control • wildlife habitat • repository of genes Fig. 31-1 Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Ecosystems provide goods directly. • Healthy ecosystems provide a variety of resources directly to people. • Wild-caught fish enrich our diets. • Hunting for food and sport is important to the economy of many rural areas. • Forests provide wood for housing and furniture. • Wild plants are a source of medicines. Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Ecosystems also benefit people indirectly. • Soil formation • Soil, with its diverse community of decomposers and detritus feeders, plays a major role in breaking down wastes and recycling nutrients. • We rely on soils to decompose waste products from industry, sewage, agriculture, and forestry. • Thus, soil serves some of the same functions as a water purification plant. Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Ecosystems also benefit people indirectly (continued). • Erosion and flood control • Grassland and forest plants block winds that would otherwise blow away soil. • The plant’s roots stabilize the soil and increase its ability to hold water, reducing both soil erosion and flooding. Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Conversion of forests to farmland can greatly increase rain runoff and soil erosion, resulting in flooding. Fig. 31-2a Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Erosion and flood control (continued) • Wetland ecosystems (marshes) reduce flooding because they act like enormous sponges that absorb storm water. • The loss of this protective function was illustrated by the catastrophic flooding of New Orleans during Hurricane Katrina in 2005. • Prior to dredging the waters of the Mississippi River, the river produced a natural silt-laden wetlands that served as a natural barrier to the force of incoming storms. Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? The levees built to replace this ecosystem service did not hold during the hurricane, and as a consequence, 80% of the city was flooded. Fig. 31-2b Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Climate regulation • By providing shade, moderating temperature, and serving as windbreaks, plant communities have a major impact on local climates. • Forests have dramatic effects on the water cycle, returning water to the atmosphere through transpiration. Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Genetic resources • Our food supply depends on a small number of domesticated species; 75% of human food is supplied by only 12 food crops. • Such heavy dependence on just a few species leaves our food security vulnerable to pests or disease epidemics that attack the key crops. • The best protection against such a potential catastrophe would be to increase food crop diversity by developing wild plants into new food sources. Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Recreation • Ecotourism, in which people travel to observe unique biological communities, is a rapidly growing industry worldwide. • Examples of ecotourism destinations include tropical coral reefs and rainforests, the Galapagos Islands, the African savanna, and even Antarctica. Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Ecological economies recognizes the monetary value of ecosystem services. • The emerging discipline of ecological economics attempts to establish the monetary value of ecosystem services, and to assess the economic trade-offs that occur when ecosystems are damaged to make way for profit-making activities. Copyright © 2009 Pearson Education Inc. 31.2 Why Is Biodiversity Important? Ecological economies recognizes the monetary value of ecosystem services (continued). • A farmer planning to divert water from a wetland to irrigate a crop would weigh the monetary value of increased crop production against the cost of the labor and machinery needed to divert the wetland’s water. Copyright © 2009 Pearson Education Inc. 31.3 Is Earth’s Biodiversity Diminishing? Extinction is a natural process, but rates have risen dramatically. • The fossil record indicates that, in the absence of cataclysmic events, extinctions occur naturally at a very low rate. • However, there are occasional mass extinctions, in which many species were eradicated in a relatively short time. • Five such mass extinction episodes have occurred; the most recent took place about 65 million years ago and abruptly ended the age of the dinosaurs. Copyright © 2009 Pearson Education Inc. 31.3 Is Earth’s Biodiversity Diminishing? Extinction is a natural process, but rates have risen dramatically (continued). • The causes of mass extinction are uncertain, but sudden changes in the environment, such as would happen by enormous meteor impacts or rapid climate change, are the most likely explanations. • Most biologists have concluded that we are now in the midst of the sixth mass extinction— this one caused by human activities. Copyright © 2009 Pearson Education Inc. 31.3 Is Earth’s Biodiversity Diminishing? Extinction is a natural process, but rates have risen dramatically (continued). • The World Conservation Union (IUCN) estimates that the current extinction rate is between 100 and 1,000 times greater than the background rate expected in the absence of people. Copyright © 2009 Pearson Education Inc. 31.3 Is Earth’s Biodiversity Diminishing? Increasing numbers of species are threatened with extinction. • Species may be described as critically endangered, endangered, or vulnerable, depending on how likely they are to become extinct in the near future. • Species that fall into any of the three categories above are described as threatened. • In 2007, 16,306 species were considered threatened, including 12% of all birds, 20% of mammals, and 29% of amphibians. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? The greatest hazards to biodiversity are posed by habitat destruction, overexploitation, invasive species, pollution, and global warming. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Habitat destruction is the most serious threat to biodiversity. • Habitat is destroyed as rivers are dammed, wetlands are drained, and grasslands and forests are converted to agriculture, roads, housing, and industry. • Since people began to farm around 11,000 years ago, Earth has lost about half of its forests. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Approximately half of all tropical rain forests have been cut down in the past 50 years. Fig. 31-4 Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Even when a natural ecosystem is not completely destroyed, it may become split into small pieces surrounded by regions devoted to human activities. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? This habitat fragmentation can be a serious threat to wildlife by making populations that are too small to survive. Fig. 31-5 Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? To be functional, a preserve must support a minimum viable population (MVP). • This is the smallest isolated population that can persist, despite the effects of inbreeding and potential disruptions from disease, fires, and floods. • The MVP for a species is influenced by many factors, including the quality of the environment, the species’ average lifespan, its fertility, and how many young usually reach maturity. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? PLAY Animation—Habitat Destruction and Fragmentation Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Overexploitation threatens many species. • Overexploitation refers to hunting or harvesting natural populations at a rate that exceeds their ability to replenish their numbers. • Overexploitation has increased as growing demand is coupled with technological advances that greatly increase our efficiency at harvesting wild animals and plants. • The IUNC estimates that overexploitation impacts about 30% of threatened mammals and birds. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Over-fishing is the single greatest threat to marine life, causing dramatic declines of many species, including cod, sharks, red snapper, swordfish, and tuna. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Most species of marine turtles are endangered as a result of over harvesting of both adults and their eggs. Fig. 31-6 Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? On land, rapidly growing populations in lessdeveloped countries increase the demand for wild animal products, as hunger and poverty drive people to harvest all that can be eaten or sold, legally or illegally, without regard to its rarity. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Invasive species displace native wildlife and disrupt community interactions. • Humans transport many species around the world, and in many cases, they cause no harm. • But sometimes, non-native species become invasive; they increase in number at the expense of native species, competing for food or habitat, or preying on them directly. • Introduced species can make native species vulnerable to extinction. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Invasive species displace native wildlife and disrupt community interactions (continued). • Island species are particularly vulnerable to competition and predation from introduced species. • In Hawaii, 99% of the 415 threatened plants and all but one of its 42 threatened bird species are endangered by invasive species. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Mongoose were introduced in the 1800s and now threaten Hawaii’s native birds. Fig. 31-7 Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Pollution is a multifaceted threat to biodiversity. • Pollutants include synthetic chemicals such as plasticizers, flame retardants, and pesticides that enter the air, soil, and water and then accumulate to toxic levels in animal tissues. • Naturally occurring substances, such as mercury, lead, and arsenic are also toxic to both people and wildlife. • Others become pollutants by disrupting biogeochemical cycles, such as the release of oxidized nitrogen and sulfur that takes place during combustion of fossil fuels, causing acid rain. Copyright © 2009 Pearson Education Inc. 31.4 What Are The Major Threats To Biodiversity? Global warming is an emerging threat to biodiversity. • The use of fossil fuels, coupled with deforestation, has increased atmospheric carbon dioxide levels. • This increase has been accompanied by increasing global temperatures. • Global warming may be causing more extreme weather, such as heat waves, droughts, floods, and stronger hurricanes. • Global warming is as great a threat to biodiversity as is habitat destruction. Copyright © 2009 Pearson Education Inc. 31.5 How Can Conservation Biology Help To Preserve Biodiversity? Conservation biology is an integrated science. • Effective conservation depends on consensus and broad participation, so conservation biologists seek expertise and support from people outside of science. • These people include government leaders, environmental lawyers, and ecological economists. • Conservation biologists collaborate with social scientists and educators who help the public understand how ecosystems function and how people can preserve them. Copyright © 2009 Pearson Education Inc. 31.5 How Can Conservation Biology Help To Preserve Biodiversity? Conserving wild ecosystems • Core reserves preserve all levels of biodiversity. • Core reserves are natural areas protected from most human uses, except low-impact recreation. • These reserves encompass enough space to preserve ecosystems and all their biodiversity. • To establish effective core reserves, conservationists must know the minimum critical areas required to sustain minimum viable populations of the species that require the most space. Copyright © 2009 Pearson Education Inc. 31.5 How Can Conservation Biology Help To Preserve Biodiversity? Corridors connect critical animal habitats. • To compensate for limits on the size of core reserves, it is necessary to establish wildlife corridors, which are strips of protected land linking core reserves. • Such corridors allow animals to move freely and safely between habitats that would otherwise be isolated by human activities. Copyright © 2009 Pearson Education Inc. 31.5 How Can Conservation Biology Help To Preserve Biodiversity? Corridors effectively increase the size of core reserves by connecting them. Fig. 31-8 Copyright © 2009 Pearson Education Inc. 31.5 How Can Conservation Biology Help To Preserve Biodiversity? Corridors connect critical animal habitats (continued). • A wildlife corridor can be as narrow as an underpass beneath a highway. • Studies showed that a cougar was using an underpass to move between suitable habitats, and it is now an official wildlife corridor and is being restored to a more natural state, encouraging cougars and other animals to cross safely beneath the freeway. Copyright © 2009 Pearson Education Inc. 31.5 How Can Conservation Biology Help To Preserve Biodiversity? Wildlife corridors Fig. 31-9 Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Natural ecosystems share the following features that allow the ecosystem to persist and flourish. • Diverse communities with rich, complex community interactions • Relatively stable population sizes • Recycling and efficient use of raw materials • Reliance on renewable sources of energy Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Sustainable living and sustainable development promote long-term ecological and human well being. • Respect for nature’s operating principles is central to sustainability. • In a landmark document, Caring for the Earth, the IUCN states that sustainable development “meets the needs of the present without compromising the ability of future generations to meet their own needs.” • It explains that humanity must take no more from nature than nature can replenish. Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Sustainable living and sustainable development promote long-term ecological and human well being (continued). • Commercial fishing is a prime example of technology working outside of nature’s limits. • Sustainable fishing requires that we preserve spawning grounds, limit fish catches, and improve technology to avoid unintended damage. Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? As individuals and governments recognize the need to change, there are increasing numbers of projects that are intended to meet human needs sustainably. Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Biosphere reserves provide models for conservation and sustainable development. • A world network of biosphere reserves has been designated by the United Nations. • The goal of biosphere reserves is to maintain biodiversity and to evaluate techniques for sustainable human development while preserving local cultural values. Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Biosphere reserves consist of three regions. • A central core reserve that while protected, allows research and sometimes tourism, as well as some sustainable traditional uses. • A surrounding buffer zone permits low-impact human activities and development. • Outside the buffer zone is a transition area that supports settlements, tourism, fishing, and agriculture, all operated sustainably. Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Biosphere reserves (continued) • Biosphere reserves are entirely voluntary and are managed by the countries and regional areas where they are located. • In many cases, much of the land in the buffer and transition zones is privately owned, and some landowners may be unaware of its designation. • The concept of the biosphere reserve is an elegant model for conservation in the context of sustainable development, and it provides a framework for both present and future efforts. Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Sustainable agriculture helps preserve natural communities. • The greatest loss of habitat occurs when people convert natural ecosystems to monoculture farming, in which large expanses of land are devoted to single crops. • Farmers face pressure to produce large amounts of food at the lowest possible cost, and in some cases, this has led to unsustainable farming that interferes with ecosystem services. Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Sustainable agriculture helps preserve natural communities (continued). • Farmers are increasing recognizing that sustainable agriculture ultimately saves money while preserving the land. • The no-till cropping technique, which leaves the remains of harvested crops in the fields to form mulch for the next year’s crops, is one component of sustainable agriculture. Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? No-till crops Fig. 31-10 Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Sustainable agriculture helps preserve natural communities (continued). • Most no-till farmers still use herbicides and pesticides. • Organic farmers also often use no-till methods, but do not use synthetic herbicides, insecticides, or fertilizers. • Organic farming relies on natural predators to control pests, and on soil microorganisms to degrade animal and crop wastes, thereby recycling their nutrients. Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Changes in lifestyle and use of appropriate technologies are also essential. • Government policies and institutional changes are vital for a sustainable future, but individual choices are also important. • We can reduce our consumption of energy and nonrenewable fossil fuels by conserving and by using energy-saving technologies. • Our choices as consumers can provide markets for foods and durable goods that are produced sustainably. Copyright © 2009 Pearson Education Inc. 31.6 Why Is Sustainability The Key To Conservation? Human population growth is unsustainable. • The root cause of environmental degradation is simple: too many people using too many resources and generating too much waste. • Through technological advances and by depleting the Earth’s ecological capital, we have achieved a population that far exceeds being in balance with the natural ecosystems on this planet. • Adding 80 million more people to Earth every year is incompatible with saving what is left of Earth’s biodiversity for those who are yet to come. Copyright © 2009 Pearson Education Inc.