Biodiversity Crisis and Conservation: Addressing Threats to Species and Ecosystems

1. Chapter 55 Conservation Biology and Restoration Ecology

2. Overview: The Biodiversity Crisis • Conservation biology integrates the following fields to conserve biological diversity at all levels • Ecology • Evolutionary biology • Physiology • Molecular biology • Genetics • Behavioral ecology

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

4. Figure 55.1 • Tropical forests • Contain some of the greatest concentrations of species • Are being destroyed at an alarming rate

5. Throughout the biosphere, human activities • Are altering ecosystem processes on which we and other species depend

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

7. Genetic diversity in a vole population Species diversity in a coastal redwood ecosystem Community and ecosystem diversity across the landscape of an entire region Figure 55.2 The Three Levels of Biodiversity • Biodiversity has three main components • Genetic diversity • Species diversity • Ecosystem diversity

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

9. Species Diversity • Species diversity • Is the variety of species in an ecosystem or throughout the biosphere

10. An endangered species • Is one that is in danger of becoming extinct throughout its range • Threatened species • Are those that are considered likely to become endangered in the foreseeable future

11. Conservation biologists are concerned about species loss • Because of a number of alarming statistics regarding extinction and biodiversity

12. (a) Philippine eagle (b) Chinese river dolphin (c) Javan rhinoceros Figure 55.3a–c • Harvard biologist E. O. Wilson has identified the Hundred Heartbeat Club • Species that number fewer than 100 individuals and are only that many heartbeats from extinction

13. Ecosystem Diversity • Ecosystem diversity • Identifies the variety of ecosystems in the biosphere • Is being affected by human activity

14. Biodiversity and Human Welfare • Human biophilia • Allows us to recognize the value of biodiversity for its own sake • Species diversity • Brings humans many practical benefits

15. Figure 55.4 Benefits of Species and Genetic Diversity • Many pharmaceuticals • Contain substances originally derived from plants

16. The loss of species • Also means the loss of genes and genetic diversity • The enormous genetic diversity of organisms on Earth • Has the potential for great human benefit

17. Ecosystem Services • Ecosystem services encompass all the processes • Through which natural ecosystems and the species they contain help sustain human life on Earth

18. Ecosystem services include • Purification of air and water • Detoxification and decomposition of wastes • Cycling of nutrients • Moderation of weather extremes • And many others

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

20. Habitat Destruction • Human alteration of habitat • Is the single greatest threat to biodiversity throughout the biosphere • Massive destruction of habitat • Has been brought about by many types of human activity

21. Figure 55.5 • Many natural landscapes have been broken up • Fragmenting habitat into small patches

22. In almost all cases • Habitat fragmentation and destruction leads to loss of biodiversity

23. Introduced Species • Introduced species • Are those that humans move from the species’ native locations to new geographic regions

24. (a) Brown tree snake, intro- duced to Guam in cargo Figure 55.6a, b (b) Introduced kudzu thriving in South Carolina • Introduced species that gain a foothold in a new habitat • Usually disrupt their adopted community

25. Overexploitation • Overexploitation refers generally to the human harvesting of wild plants or animals • At rates exceeding the ability of populations of those species to rebound

26. Figure 55.7 • The fishing industry • Has caused significant reduction in populations of certain game fish

27. Figure 55.8 Disruption of Interaction Networks • The extermination of keystone species by humans • Can lead to major changes in the structure of communities

28. 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

29. Small-Population Approach • Conservation biologists who adopt the small-population approach • Study the processes that can cause very small populations finally to become extinct

30. Small population Genetic drift Inbreeding Lower reproduction Higher mortality Loss of genetic variability Reduction in individual fitness and population adaptability Smaller population Figure 55.9 The Extinction Vortex • A small population is prone to positive-feedback loops • That draw the population down an extinction vortex

31. The key factor driving the extinction vortex • Is the loss of the genetic variation necessary to enable evolutionary responses to environmental change

32. 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

33. As a test of the extinction vortex hypothesis • Scientists imported genetic variation by transplanting birds from larger populations

34. EXPRIMENT 200 Researchers observed that the population collapse of the greater prairie chicken was mirrored in a reduction in fertility, as measured by the hatching rate of eggs. Comparison of DNA samples from the Jasper County, Illinois, population with DNA from feathers in museum specimens showed that genetic variation had declined in the study population. In 1992, researchers began experimental translocations of prairie chickens from Minnesota, Kansas, and Nebraska in an attempt to increase genetic variation. 150 Number of male birds 100 50 0 1970 1975 1980 1985 1990 1995 2000 RESULTS After translocation (blue arrow), the viability of eggs rapidly improved, and the population rebounded. Year (a) Population dynamics 100 90 80 70 60 Eggs hatched (%) 50 CONCLUSION The researchers concluded that lack of genetic variation had started the Jasper County population of prairie chickens down the extinction vortex. 40 30 1980-84 1985-89 1990 1993-97 1970-74 1975-79 Years (b) Hatching rate Figure 55.10 • The declining population rebounded • Confirming that it had been on its way down an extinction vortex

35. Minimum Viable Population Size • The minimum viable population (MVP) • Is the minimum population size at which a species is able to sustain its numbers and survive

36. A population viability analysis (PVA) • Predicts a population’s chances for survival over a particular time • Factors in the MVP of a population

37. Effective Population Size • A meaningful estimate of MVP • Requires a researcher to determine the effective population size, which is based on the breeding size of a population

38. Figure 55.11 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

39. 150 Females with cubs Cubs 100 Number of individuals 50 0 1973 1991 1982 2000 Year Figure 55.12 • This study has shown that the grizzly bear population • Has grown substantially in the past 20 years

40. 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 in the first place

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

42. (a) A red-cockaded woodpecker perches at the entrance to its nest site in a longleaf pine. (b) Forest that can sustain red-cockaded woodpeckers has low undergrowth. (c) Forest that cannot sustain red-cockaded woodpeckers has high, dense undergrowth that impacts the woodpeckers’ access to feeding grounds. Figure 55.13a–c Case Study: Decline of the Red-Cockaded Woodpecker • Red-cockaded woodpeckers • Require specific habitat factors for survival • Had been forced into decline by habitat destruction

43. In a study where breeding cavities were constructed • New breeding groups formed only in these sites • On the basis of this experiment • A combination of habitat maintenance and excavation of new breeding cavities has enabled a once-endangered species to rebound

44. Weighing Conflicting Demands • Conserving species often requires resolving conflicts • Between the habitat needs of endangered species and human demands

45. Concept 55.3: Landscape and regional conservation aim to sustain entire biotas • In recent years, conservation biology • Has attempted to sustain the biodiversity of entire communities, ecosystems, and landscapes

46. One goal of landscape ecology, of which ecosystem management is part • Is to understand past, present, and future patterns of landscape use and to make biodiversity conservation part of land-use planning

47. Landscape Structure and Biodiversity • The structure of a landscape • Can strongly influence biodiversity

48. (a) Natural edges. Grasslands give way to forest ecosystems in Yellowstone National Park. (b) Edges created by human activity. Pronounced edges (roads) surround clear-cuts in this photograph of a heavily logged rain forest in Malaysia. Figure 55.14a, b Fragmentation and Edges • The boundaries, or edges, between ecosystems • Are defining features of landscapes

49. As habitat fragmentation increases • And edges become more extensive, biodiversity tends to decrease

50. Figure 55.15 • Research on fragmented forests has led to the discovery of two groups of species • Those that live in forest edge habitats and those that live in the forest interior