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Biological Sciences

Chapter 57: Conservation Biology 57.1 What is Conservation Biology? • Devoted to preserving the diversity of life on Earth • Draws heavily on concepts and knowledge from population genetics, evolution, ecology, biogeography, wildlife management, economics and sociology Conservation biology is a normative scientific discipline • Conservation biology is a normative discipline embraces certain values and applies scientific methods to the goal of achieving these values; motivated by the belief that preservation of biodiversity is good and that loss is bad. • Is guided by three principles: o Evolution is a process that unites all of biology. o The ecological world is dynamic. o Humans are a part of ecosystems. Conservation biology aims to prevent species extinctions • Organisms have always altered Earth’s ecosystems. • Very first organisms probably reduced the supply of energetically and structurally useful compounds (replacing them with waste products). • Early photosynthetic prokaryotes and eukaryotes generated oxygen (unsuitable for anaerobic organisms). • Plants colonized the land, accelerating the weathering of rocks thus, gaining access to rock-bound nutrients. • Weathering of phosphorus increased global productivity = rise of oxygen concentrations. • Rise of vascular plants increased oxygen concentration; lower carbon dioxide concentrations. • Human beings cause extinctions of other species o When first arrived in N. America (20 000 years ago), encountered a rich fauna of large mammals. o Most species were exterminated (overhunting) within a few thousand years. • The productivity and richness of Earth’s biota has increased during the long course of life’s evolution, but current situation is unique: all environmental changes are being caused by a single species. • That’s why now more and more people value biodiversity for many reasons: o Humans depend on other species for food, fiber, and medicine o Species are necessary for the functioning of ecosystems and its many benefits and services. o Humans derive enormous aesthetic pleasure from interacting with other organisms. o Extinctions deprive us of opportunities to study and understand ecological relationships among organisms. o Living in ways that cause the extinction of other species raises serious ethical issues 57.2 How Do Biologists Predict Changes in Biodiversity? • To preserve Earth’s biodiversity, we need to both maintain the processes that generate new species and provide conditions that will keep extinction rates at a typical level • There are four reasons why scientists cannot accurately predict the number of future extinctions: o Do not know how many species live on Earth. o Do not know where species live (i.e. animal ranges are poorly known). o Difficult to determine when a species actually becomes extinct. o Do not know what will happen in the future. • Regardless, there are some methods for estimating probable rates of extinction resulting from human actions (e.g. habitat destruction). • Species area relationship—mathematical relationship between the size of an area and the number of species that area contains. • Findings suggest that a 90 percent loss of habitat will result in the loss of half of the species that live in and depend on that habitat. • Current rate of loss of tropical evergreen forests is about 2% of remaining forest each year; if this continues, at least 1 million species there could become extinct during this century. • To estimate the risk that a population will become extinct, conservation biologists develop statistical models that incorporate information about pop. size, its genetic variation, and the morphology, physiology and behaviour of its members. • Species in imminent danger of extinction in all or a significant part of their range are labelled endangered species. • Threatened species are likely to become endangered in the near future. • Rarity is not ALWAYS a cause for concern b/c some species that live in highly specialized habitats (e.g. panda) have probably always been rare and are well adapted to those conditions. • Species whose populations suddenly shrink at rapid rates (i.e. “newly rare”) are usually at high risks. • Species with special habitats or dietary requirements are more likely to become extinct that species with more generalized requirements. • Populations with only a few individuals confined to a small range can easily be eliminated by local disturbances. 57.3 What Factors Threaten Species Survival? Species are endangered by habitat loss, degradation, and fragmentation • Habitat loss is the most important cause of species endangerment. • A habitat loss also affects the remaining habitats that are not destroyed. • As habitats are progressively lost, the remaining habitat patches become smaller and more isolated and becomes increasingly fragmented. • Small habitat patches are qualitatively different from larger patches of the same habitat in ways that affect the survival of species. • Small patches cannot maintain populations of species that require large areas; can support only small populations of many of the species that can survive in small patches. • The fraction of a patch that is influenced by factors originating outside it increases rapidly as patch size decreases  So, species from surrounding habitats often colonize the edges of patches to compete with or prey on the species living there, edge effects. • Species that are lost from small habitat fragments are unlikely to become re- established there because dispersing individuals are unlikely to find isolated fragments. • BUT species may persist in a small patch if it is connected to other patches by corridors of habitat through which individuals can disperse. Overexploitation has driven many species to extinction • Elephants and rhinoceroses are threatened in much of Africa and Asia b/c poachers kill them for their tusks and horns. • The use of animal parts in traditional medical practices is a threat to some species. Invasive predators, competitors, and pathogens threaten many species • People have moved many species to regions outside their original range, deliberately or accidentally.
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