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Chapter 55

Chapter 55. Conservation Biology and Restoration Ecology. Overview: The Biodiversity Crisis. Conservation biology integrates these fields: Ecology Evolutionary biology Physiology Molecular biology Genetics Behavioral ecology.

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Chapter 55

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  1. Chapter 55 Conservation Biology and Restoration Ecology

  2. Overview: The Biodiversity Crisis • Conservation biology integrates these fields: • Ecology • Evolutionary biology • Physiology • Molecular biology • Genetics • Behavioral ecology

  3. Restoration ecology applies ecological principles to return degraded ecosystems to conditions as similar as possible to their natural state

  4. Tropical forests containing some of the greatest concentrations of species are being destroyed at an alarming rate • Throughout the biosphere, human activities are altering ecosystem processes on which we and other species depend

  5. Concept 55.1: Human activities threaten Earth’s biodiversity • Rates of species extinction are difficult to determine under natural conditions • The high rate of species extinction is largely a result of ecosystem degradation by humans • Humans are threatening Earth’s biodiversity

  6. The Three Levels of Biodiversity • Biodiversity has three main components: • Genetic diversity • Species diversity • Ecosystem diversity

  7. LE 55-2 Genetic diversity in a vole population Species diversity in a coastal redwood ecosystem Community and ecosystem diversity across the landscape of an entire region

  8. Genetic Diversity • Genetic diversity comprises genetic variation within a population and between populations

  9. Species Diversity • Species diversity is the variety of species in an ecosystem or throughout the biosphere • An endangered species is in danger of becoming extinct throughout its range • A threatened species is likely to become endangered in the future

  10. Conservation biologists are concerned about species loss because of alarming statistics regarding extinction and biodiversity • Researchers estimate that at current rates of extinction more than half of current plant and animal species will disappear in this century • Harvard biologist E. O. Wilson has identified the Hundred Heartbeat Club: species with fewer than 100 individuals

  11. LE 55-3 Philippine eagle Chinese river dolphin Javan rhinoceros

  12. Ecosystem Diversity • Human activity is reducing ecosystem diversity, the variety of ecosystems in the biosphere

  13. Biodiversity and Human Welfare • Human biophilia allows us to recognize the value of biodiversity for its own sake • Species diversity brings humans practical benefits

  14. Benefits of Species and Genetic Diversity • Many pharmaceuticals contain substances originally derived from plants • For example, the rosy periwinkle contains alkaloids that inhibit cancer growth

  15. The loss of species also means loss of genes and genetic diversity • The enormous genetic diversity of organisms has potential for great human benefit

  16. Ecosystem Services • Ecosystem services encompass all the processes through which natural ecosystems and their species help sustain human life • Some examples of ecosystem services: • Purification of air and water • Detoxification and decomposition of wastes • Cycling of nutrients • Moderation of weather extremes

  17. Four Major Threats to Biodiversity • Most species loss can be traced to four major threats: • Habitat destruction • Introduced species • Overexploitation • Disruption of “interaction networks”

  18. Habitat Destruction • Human alteration of habitat is the greatest threat to biodiversity throughout the biosphere • Many natural landscapes have been broken up, fragmenting habitat into small patches • In almost all cases, habitat fragmentation and destruction lead to loss of biodiversity

  19. Introduced Species • Introduced species are those that humans move from native locations to new geographic regions • Introduced species that gain a foothold in a new habitat usually disrupt their adopted community

  20. Sometimes humans introduce species by accident, as in case of the brown tree snake arriving in Guam as a cargo ship “stowaway”

  21. LE 55-6 Brown tree snake, intro- duced to Guam in cargo. Introduced kudzu thriving in South Carolina

  22. Humans have deliberately introduced some species with good intentions but disastrous effects • An example is the introduction of kudzu in the southern United States

  23. Overexploitation • Overexploitation is human harvesting of wild plants or animals at rates exceeding the ability of populations of those species to rebound • For example, the fishing industry has greatly reduced populations of some game fish, such as bluefin tuna

  24. Disruption of Interaction Networks • Extermination of keystone species by humans can lead to major changes in community structure

  25. Concept 55.2: Population conservation focuses on population size, genetic diversity, and critical habitat • Biologists focusing on conservation at the population and species levels follow two main approaches: • The small-population approach • The declining population approach

  26. Small-Population Approach • The small-population approach studies processes that can make small populations become extinct

  27. The Extinction Vortex • A small population is prone to positive-feedback loops that draw it down an extinction vortex

  28. LE 55-9 Small population Genetic drift Inbreeding Lower reproduction Higher mortality Loss of genetic variability Reduction in individual fitness and population adaptability Smaller population

  29. The key factor driving the extinction vortex is loss of the genetic variation necessary to enable evolutionary responses to environmental change

  30. Case Study: The Greater Prairie Chicken and the Extinction Vortex • Populations of the greater prairie chicken were fragmented by agriculture and later found to exhibit decreased fertility • To test the extinction vortex hypothesis, scientists imported genetic variation by transplanting birds from larger populations • The declining population rebounded, confirming it had been on its way down an extinction vortex

  31. LE 55-10 200 150 Number of male birds 100 50 0 1980 1985 1970 1975 1990 1995 2000 Year Population dynamics 100 90 80 70 Eggs hatched (%) 60 50 40 30 1993–97 1970–74 1975–79 1980–84 1985–89 1990 Years Hatching rate

  32. Minimum Viable Population Size • Minimum viable population (MVP) is the minimum population size at which a species can survive • The MVP factors into a population viability analysis (PVA), which predicts a population’s chances for survival over a particular time

  33. Effective Population Size • A meaningful estimate of MVP requires determining the effective population size, which is based on the population’s breeding size

  34. Case Study: Analysis of Grizzly Bear Populations • One of the first population viability analyses was conducted as part of a long-term study of grizzly bears in Yellowstone National Park

  35. This study showed that the grizzly bear population has grown substantially in the past 20 years

  36. LE 55-12 150 Females with cubs Cubs 100 Number of individuals 50 0 1973 2000 1982 1991 Year

  37. Declining-Population Approach • The declining-population approach • Focuses on threatened and endangered populations that show a downward trend, regardless of population size • Emphasizes the environmental factors that caused a population to decline

  38. Steps for Analysis and Intervention • The declining-population approach • Requires that declines in population be evaluated on a case-by-case basis • Involves a step-by-step proactive conservation strategy

  39. Case Study: Decline of the Red-Cockaded Woodpecker • Red-cockaded woodpeckers had been forced into decline by habitat destruction

  40. LE 55-13 A red-cockaded woodpecker perches at the entrance to its nest site in a longleaf pine. Forest that cannot sustain red-cockaded woodpeckers has high, dense undergrowth that impacts the woodpeckers’ access to feeding grounds. Forest that can sustain red-cockaded woodpeckers has low undergrowth.

  41. In a study where breeding cavities were constructed, new breeding groups formed only in these sites • Based on this experiment, a combination of habitat maintenance and excavation of breeding cavities enabled this endangered species to rebound

  42. Weighing Conflicting Demands • Conserving species often requires resolving conflicts between habitat needs of endangered species and human demands

  43. Concept 55.3: Landscape and regional conservation aim to sustain entire biotas • Conservation biology has attempted to sustain the biodiversity of entire communities, ecosystems, and landscapes • Ecosystem management is part of landscape ecology, which seeks to make biodiversity conservation part of land-use planning

  44. Landscape Structure and Biodiversity • The structure of a landscape can strongly influence biodiversity

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