Conservation Biology

1. Conservation Biology

2. Conservation Biology • Introduction • Why Care about Species Extinctions? • Estimating Current Rates of Extinction • Preserving Biodiversity • Habitat Restoration and Species Recovery • Healing Biotas: Conservation Medicine • Setting Limits: The Legacy of Samuel Plimsoll

3. Introduction • The problem of human-caused extinction of species led to the development of the discipline of conservation biology: the scientific study of how to preserve the diversity of life. • Conservation biology draws on population genetics, evolution, biogeography, wildlife management, economics, and sociology.

4. Why Care about Species Extinctions? • The value of biodiversity to humans: • Humans depend on other species for food, fiber, and medicine. • Humans derive aesthetic pleasure from interacting with other organisms. • Causing the extinction of other species raises serious ethical issues. • Extinctions make the study of ecological relationships and species interactions difficult. • Species are necessary for the function of the ecosystems of which they are a part.

5. Why Care about Species Extinctions? • The benefits provided to humans by functioning ecosystems are enormous. • These include, among others, prevention of soil erosion, regulation of hydrologic cycles, and detoxification and recycling of waste products.

6. Why Care about Species Extinctions? • In Western Cape Province, South Africa, preservation of the native ecosystem is vital to maintaining the water supply of the area. • The native vegetation of the highlands is a species-rich community of shrubs called fynbos that can survive drought, nutrient-poor soils, and fire. The highlands provide two thirds of Western Cape’s water. • The fynbos also provides income in the form of cut flowers and tourism. • The native vegetation is being displaced by introduced plants that grow taller and faster, increase the intensity of fires, and reduce the water supply.

7. Figure 57.1 Invasive Species Disrupt Ecosystem Function (Part 1)

8. Why Care about Species Extinctions? • By removing the exotic plants and managing fire, the natural fynbos ecosystem can be preserved. • High-tech approaches to replacing water (such as sewage purification plants and desalinization) would cost between 1.8 and 6.7 times as much as maintaining natural vegetation in the watershed.

9. Estimating Current Rates of Extinction • The number of species on an island increases with the size of the island. • Conservation biologists have applied this species–area relationship to habitat patches on the mainland as well. • Findings suggest that a 90% loss of habitat will result in the loss of half of the species living there. • If the current rate continues, about 1 million species living in the tropical evergreen forests will become extinct in this century.

10. Estimating Current Rates of Extinction • To assess extinction risk for a population, biologists analyze many factors including genetic variation, morphology, physiology, behavior, and environment. • Species in imminent danger over a significant portion of their range are labeled endangered species. • Species that are likely to become endangered in the near future are labeled threatened species.

11. Estimating Current Rates of Extinction • Rarity is not always a reason for concern. • However, species in which a few individuals are confined to a small range are more likely to be eliminated by local disturbances such as fire and disease. • A 12-year study of grizzly bears in Yellowstone National Park suggested that for the bears to have a 95% chance of survival for 100 years, there must be habitat to support 70–90 bears. • To achieve a higher probability of survival, or survival for a longer time, more bear habitat would be needed.

12. Preserving Biodiversity • The human activities that threaten species include habitat destruction, introduction of invasive species, overexploitation, disease, alteration of disturbance patterns, and climate change. • Conservation biologists determine how these activities are affecting species and devise strategies to preserve endangered or threatened species.

13. Preserving Biodiversity • Habitat loss is the most important cause of endangerment of species in the U.S., especially species that live in fresh waters. • As habitats are destroyed, the remaining patches become fragmented (smaller and more isolated). • Small patches cannot maintain populations that require larger areas and can support only small numbers of species that can survive in them.

14. Figure 57.2 Proportions of U.S. Species Extinct or in Peril

15. Preserving Biodiversity • The fraction of a habitat patch that is influenced by adjacent habitat conditions (edge effects) increases rapidly as patch size decreases. • Close to the edges of a forest patch, for example, the environment differs from that inside the forest, so species from surrounding habitats colonize the edges to compete with or prey upon those inside.

16. Figure 57.3 Edge Effects

17. Preserving Biodiversity • Usually it is not known which organisms lived in an area before their habitats became fragmented. • A major research project in Manaus, Brazil, was undertaken to examine the effects of habitat fragmentation. • Landowners agreed to preserve forest patches of certain sizes and configurations. • Biologists examined species diversity before and after logging around the patches. • Species began to disappear from the isolated patches soon after the surrounding forest was cut.

18. Figure 57.4 Brazilian Forest Fragments Studied for Species Loss

19. Preserving Biodiversity • Species that become extinct in small patches are unlikely to be reestablished, but corridors between patches can allow individuals to disperse and species to persist. • In Brazil, within 7–9 years of having abandoned the logged patches, birds reestablished themselves in the young forest that grew up.

20. Preserving Biodiversity • People have moved organisms between continents deliberately and accidentally. • A species that has evolved in a community and become accustomed to the natural predators or competitors may be driven to extinction by newly introduced predators or competitors. • A major human-caused environmental change is the introduction of non-native species that then become invasive in the their new environments.

21. Preserving Biodiversity • Hundreds of species of plants have been introduced as ornamentals. An example is purple loosestrife. • Almost half of the medium-sized marsupials in Australia have become extinct due to the introduction of predators (cats and foxes) and competitors (rabbits) to the continent. • Proliferation of introduced pathogens, such as the fungus that causes Dutch elm disease, has caused much destruction to North American forests.

22. Preserving Biodiversity • The best way to reduce the damage caused by invasive species is to prevent their establishment in the first place. • The shipping industry spreads invasive species in ballast water, which is pumped into ships at one port and discharged at another. Deoxygenating ballast water before it is pumped out would control the problem of invasive aquatic species. • Australia and New Zealand require a weed risk assessment for the importation of plants.

23. Preserving Biodiversity • The U.S. horticultural industry has crafted a voluntary code of conduct stating that the invasive potential of a plant should be assessed prior to its introduction and marketing. • A decision tree can be used to determine whether a species is likely to become invasive. • A plant species is more likely to become invasive if it has short generation time, small seeds, a large range, and no evolutionary relationship to plants in the new area. • Conservation biologists have developed a decision tree to determine whether exotic species can safely be introduced into North America.

24. Figure 57.5 A “Decision Tree” to Govern Introductions (Part 1)

25. Figure 57.5 A “Decision Tree” to Govern Introductions (Part 2)

26. Preserving Biodiversity • Until recently, humans caused most extinctions primarily by overhunting. • The passenger pigeon, one of the most abundant species of bird in North America in the 1800s, became extinct by 1914 due to hunting. • Elephants and rhinoceroses are threatened with extinction because poachers kill them for their tusks and horns. • The houseplant and pet trades currently threaten many species of orchids, parrots, and reptiles.

27. Preserving Biodiversity • Programs have been developed to help us use species in a way that does not threaten their survival. • Certification programs: Organizations such as the Forest Stewardship Council (FSC) and the Marine Stewardship Council determine whether commercial operations harvest and market their products in ways that meet their criteria.

28. Preserving Biodiversity • The Convention on International Trade in Endangered Species (CITES), an international organization, determines and prohibits trade in endangered species or their products (e.g., whale meat, rhinoceros horn, many parrots and orchids).

29. Preserving Biodiversity • Many species depend on particular patterns of disturbance to persist. • Humans often try to control such disturbances, but conservation biologists try to determine where disturbances should be reestablished. • For example, annual growth rings on ponderosa pines show that low-intensity fires were once common in New Mexico. • Because of sheep grazing and fire suppression, buildup of dead branches and needles has resulted in intense, tree-consuming fires. • Today ground fires are deliberately started to imitate historic patterns.

30. Figure 57.6 The Frequency and Intensity of Fires Affect Ecosystems

31. Preserving Biodiversity • Atmospheric scientists predict that average temperatures in North America will increase 2–5°C by the end of the century. • Species will need to shift their ranges as much as 500–800 km. Some habitats, such as alpine tundra, may disappear. • Knowledge of how organisms responded to past climate changes, such as postglacial warming, can help us predict the effects of the current warming. • Organisms such as birds, which have good dispersal abilities, can shift their ranges rapidly.

32. Preserving Biodiversity • Other species shift ranges much more slowly. • In North America, some species of coniferous trees expanded northward as glaciers retreated. • Earthworms disperse very slowly. Introduced earthworms from Europe are able to survive in places north of the current distribution of native earthworms. • Slow dispersal, not lack of suitable habitat, has kept native earthworms from moving northward.

33. Figure 57.7 Some Species Shift Their Ranges in Response to Climate Change (Part 1)

34. Figure 57.7 Some Species Shift Their Ranges in Response to Climate Change (Part 2)

35. Preserving Biodiversity • If Earth warms as predicted, climatic zones won’t just shift. New climates will develop and some existing climates will disappear. • New climates are likely to develop at low elevations in the tropics. A warming of even 2°C would result in climates that are warmer than any that exist today. • In 1988, the highest sea surface temperatures ever recorded caused corals to undergo bleaching and increased their mortality worldwide.

36. Figure 57.8 Global Warming Affects Corals (Part 1)

37. Figure 57.8 Global Warming Affects Corals (Part 2)

38. Habitat Restoration and Species Recovery • The field of restoration ecology has developed to study methods of restoring natural habitats. • Some damaged habits will not recover without assistance, and biologists try to maintain some endangered species in captivity until suitable habitat is available. • Conservation biologists have only a limited ability to restore natural ecosystems and many attempts have been only partially successful.

39. Habitat Restoration and Species Recovery • Wetland restoration is a high priority in southern California, where 90 percent of the coastal wetlands have been destroyed. • In early attempts at species restoration, many species failed to recolonize the wetlands. • Biologists discovered that the problem was lack of diversity in the plant species introduced. Plots later planted with species-rich mixtures developed the complex vegetation needed for birds and insects and accumulated nitrogen more quickly than the species-poor experimental communities.

40. Figure 57.9 Species Richness Enhances Wetland Restoration (Part 1)

41. Figure 57.9 Species Richness Enhances Wetland Restoration (Part 2)

42. Habitat Restoration and Species Recovery • Threatened species can sometimes be maintained in captivity while external threats to their existence are reduced or removed. • Captive propagation is a temporary measure, however, because zoos, aquariums, and botanical gardens have only a limited capacity. • Some species have benefited from captive breeding programs.

43. Habitat Restoration and Species Recovery • Captive breeding is helping to save the California condor. • The condor once ranged from British Columbia to Mexico, but by 1978 the wild population was down to about 30 birds. • Captive breeding was initiated in 1983 and by 1993 the captive breeding population was 60 birds. • Captive-bred birds were released in California and Arizona and were found to use the same roosting sites, bathing pools, and mountain ridges as their predecessors. • As of 2003 there were 81 wild condors in California and Arizona.

44. Figure 57.10 Soaring High Once More

45. Healing Biotas: Conservation Medicine • On land and sea, diseases among wild organisms are threatening biodiversity. • The Caribbean Basin and seas in the Indo-Pacific have lost corals and other organisms. • In parts of the Hawaiian Islands, nearly all endemic bird species have been eliminated by avian malaria introduced into the island by exotic birds. • The West Nile bird virus has exploded across the U.S. and has spread to humans.

46. Figure 57.11 Extinct Hawaiian Honeycreepers

47. Healing Biotas: Conservation Medicine • A new field of conservation medicine is developing to help identify the causes of increases in wildlife diseases and to devise ways to prevent transmission and limit the effects. • Molecular techniques are used to identify species, strains, and life cycles of pathogens.