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CHAPTER 36: CONSERVATION BIOLOGY 36.1 Conservation Biology and Biodiversity Conservation biology is an interdisciplinary field with the explicit goal of protecting biodiversity and Earth’s natural resources. Biodiversity At its simplest level, biodiversity is the variety of life on Earth. To develop a meaningful understanding of life on Earth, we need to know more about species than their total number. Conservation biologists describe biodiversity at three levels of biological organization: genetic diversity, ecosystem diversity, and landscape diversity. 36.2 Value of Biodiversity Biodiversity is a resource of immense value. Direct Value Various individual species perform services for human beings. Medicinal Value Most of the prescription drugs used in the United States were originally derived from living organisms. Agricultural Value Crops such as wheat, corn, and rice are derived from wild plants that have been modified. Consumptive Use Value Most freshwater and marine harvests depend on wild animals. Indirect Value These services are said to be indirect because they are pervasive and not easily discernible. Biogeochemical Cycles The biodiversity within ecosystems contributes to the workings of the various biogeochemical cycles. Waste Disposal Decomposers break down dead organic matter and other types of wastes. Provision of Fresh Water The water cycle continually supplies fresh water to terrestrial ecosystems. Forests and other natural ecosystems soak up water and then release it at a regular rate. Flood Prevention 1 Forests and other natural ecosystems exert a “sponge effect,” thereby reducing flooding. Prevention of Soil Erosion Intact ecosystems naturally retain soil and prevent soil erosion. Regulation of Climate Globally, forests ameliorate the climate because they take up carbon dioxide and release oxygen. Ecotourism In the United States nearly 100 million people enjoy vacationing in a natural setting. 36.3 Threats to Biodiversity We are presently in a biodiversity crisis—the number of extinctions expected to occur in the near future is unparalleled in Earth’s history. Habitat Loss Human occupation of the coastline, semiarid lands, tropical rain forests, and other areas are the most important cause of the loss of biodiversity. Exotic Species Exotic species are nonnative members of an ecosystem. Humans have introduced exotic species by the following means: Colonization Europeans, in particular, brought various familiar species with them when they colonized new places. Horticulture and Agriculture Some exotics now taking over vast tracts of land have escaped from cultivated areas. Accidental Transport Global trade and travel accidentally bring many new species from one country to another. Exotics on Islands Islands are particularly susceptible to environmental discord caused by the introduction of exotic species. Pollution Pollution brings about environmental changes that adversely affect the lives and health of living things. Acid Deposition 2 Acid deposition decimates forests and lakes. Eutrophication Lakes are under stress due to over-enrichment. Ozone Depletion The ozone shield protects Earth from harmful ultraviolet radiation. and Organic Chemicals Endocrine-disrupting contaminants affect the endocrine system reproductive potential of animals. Global Warming Global warming is expected to have many detrimental effects. Overexploitation Overexploitation occurs when the number of individuals taken from a wild population is so great that the population becomes severely reduced in numbers. For example, a marine ecosystem can be disrupted by over fishing. Disease Wildlife is subject to emerging diseases just as humans are. 36.4 Habitat Conservation and Restoration Habitat Conservation Because habitat loss is the leading cause of species’ extinctions, conservation of habitat is of primary concern. Some regions of the world are called biodiversity hotspots because they contain unusually large concentrations of species. We can also focus our efforts on conserving habitat for “keystone species,” or those whose loss would result in a great number of secondary extinctions. Landscape Conservation and Reserve Design Conservation often has to occur at the landscape level because sufficient habitat may not be available in a single place to sustain a viable population of a particular species. Edge Effects An edge reduces the amount of habitat typical of an ecosystem because the edges around a patch have a habitat slightly different from the interior of the patch. Reserve Design Conservation reserves are those areas that are set aside with the primary goal of protecting biodiversity within them. Habitat Restoration 3 In cases where habitat has already been modified in an area to the extent that conservation and reserve formation may not be viable, or to reverse existing damage, habitat restoration is an alternative. The Everglades Because of the huge disruptions to natural water flows, the Everglades are now dying. Restoration Plan A restoration plan has been developed that will sustain the Everglades ecosystem while maintaining the services society requires. 36.5 Working Toward a Sustainable Society A sustainable society would be able to provide the same goods and services for future generations of human beings as it does now and biodiversity would be conserved. Today’s society has several characteristics that indicate it is not sustainable. Energy Approximately 81% of the world’s energy supply comes from nonrenewable sources. Renewable Energy Sources Renewable types of energy include hydropower, geothermal energy, wind power, and solar energy. Water In some areas of the world, people do not have ready access to drinking water, and if they do, the water may be impure. Although the needs of the human population overall do not exceed the renewable supply of water, this is not the case in certain regions of the United States and the world. Conservation of Water Solutions for expanding water supplies, such as planting drought- and salt-tolerant crops, have been suggested. Agriculture Today, current agricultural practices provide enough food to provide everyone on Earth a healthy diet consisting of 2,500 calories per day. However, over 1 billion people are currently considered malnourished due to lack of proper distribution and the fact that much of the grain that is produced in MDCs is used to feed livestock rather than humans. In addition, modern farming methods are environmentally destructive in several ways. 4 Urban Growth More and more people are moving to cities and growth of cities increases pollution via many sources. 5