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Chapter 11

Chapter 11. Sustaining Biodiversity: The Species Approach. Chapter Overview Questions. How do biologists estimate extinction rates, and how do human activities affect these rates? Why should we care about protecting wild species? Which human activities endanger wildlife?

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Chapter 11

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  1. Chapter 11 Sustaining Biodiversity: The Species Approach

  2. Chapter Overview Questions • How do biologists estimate extinction rates, and how do human activities affect these rates? • Why should we care about protecting wild species? • Which human activities endanger wildlife? • How can we help prevent premature extinction of species? • What is reconciliation ecology, and how can it help prevent premature extinction of species?

  3. 9-1 What Role Do Humans Play in the Premature Extinction of Species? Concept 9-1A We are degrading and destroying biodiversity in many parts of the world, and these threats are increasing. Concept 9-1B Species are becoming extinct 100 to 1,000 times faster than they were before modern humans arrived on the earth (the background rate), and by the end of this century, the extinction rate is expected to be 10,000 times the background rate.

  4. Core Case Study: The Passenger Pigeon - Gone Forever • Once the most numerous bird on earth. • In 1858, Passenger Pigeon hunting became a big business. • By 1900 they became extinct from over-harvest and habitat loss. Figure 11-1

  5. Core Case Study: The Passenger Pigeon: Gone Forever Passenger pigeon hunted to extinction by 1900 Commercial hunters used a "stool pigeon” Archeological record shows five mass extinctions Human activities: hastening more extinctions?

  6. SPECIES EXTINCTION • Species can become extinct: • Locally: A species is no longer found in an area it once inhabited but is still found elsewhere in the world. • Ecologically: Occurs when so few members of a species are left they no longer play its ecological role. • Globally (biologically): Species is no longer found on the earth.

  7. Global Extinction • Some animals have become prematurely extinct because of human activities. Figure 11-2

  8. Human Activities Are Destroying and Degrading Biodiversity Human activity has disturbed at least half of the earth’s land surface Fills in wetlands Converts grasslands and forests to crop fields and urban areas Degraded aquatic biodiversity

  9. Extinctions Are Natural but Sometimes They Increase Sharply Background extinction: steady rate of extinctions is normal Extinction rate: number of extinctions in a given time period Mass extinction:extinction rate increases dramatically above background level – fossil record shows 5 major mass extinctions Most famous is Cretaceous extinction that wiped out the dinosaurs Biggest was Permian extinction that killed about 90% of all life, just before the dinos took over We are currently in a human-caused mass extinction

  10. Some Human Activities Cause Premature Extinctions; the Pace Is Speeding Up (1) Premature extinctions due to Habitat destruction (#1 cause) Overhunting (commercial, sport, & poaching) Pollution Invasive Species Global Warming

  11. Conservative estimates of extinction = 0.01-1.0% per year Growth of human population will increase this loss Rates are higher where there are more endangered species Tropical forests and coral reefs, wetlands and estuaries—sites of new species—being destroyed Speciation crisis: evolution of new species is too slow to make up for current extinction rate Some Human Activities Cause Premature Extinctions; the Pace Is Speeding Up (2)

  12. Endangered and Threatened Species: Ecological Smoke Alarms • Endangered species: so few individual survivors that it could soon become extinct. • Threatened species: still abundant in its natural range but is likely to become endangered in the near future. Figure 11-3

  13. Florida manatee Kirtland’s warbler Grizzly bear Knowlton cactus African elephant Swallowtail butterfly Humpback chub Utah prairie dog Siberian tiger Golden lion tamarin Fig. 11-3, p. 224

  14. Giant panda Blue whale Whooping crane Northern spotted owl Black-footed ferret Mountain gorilla Florida panther California condor Hawksbill sea turtle Black rhinoceros Fig. 11-3, p. 224

  15. SPECIES EXTINCTION • Some species have characteristics that make them vulnerable to ecological and biological extinction. Figure 11-4

  16. SPECIES EXTINCTION • Scientists use measurements and models to estimate extinction rates. • The International Union for the Conservation of Nature and Natural Resources (IUCN) publishes an annual Red List, listing the world’s threatened species. • The 2004 Red List contains 15,589 species at risk for extinction. Figure 11-5

  17. SPECIES EXTINCTION • Percentage of various species types threatened with premature extinction from human activities. Figure 11-5

  18. Science Focus: Estimating Extinction Rates Is Not Easy Three problems Hard to document due to length of time Only 1.8 million species identified Little known about nature and ecological roles of species identified Document little changes in DNA Use species–area relationship Mathematical models

  19. SPECIES EXTINCTION • Scientists use models to estimate the risk of particular species becoming extinct or endangered. Figure 11-6

  20. 9-2 Why Should We Care about Preventing Premature Species Extinction? Concept 9-2 We should prevent the premature extinction of wild species because of the economic and ecological services they provide and because they have a right to exist regardless of their usefulness to us.

  21. IMPORTANCE OF WILD SPECIES • We should not cause the premature extinction of species because of the economic and ecological services they provide. • Some believe that each wild species has an inherent right to exist. • Some people distinguish between the survival rights among various types of species (plants vs. animals).

  22. Species Are a Vital Part of the Earth’s Natural Capital Instrumental value Use value Ecotourism: wildlife tourism Genetic information Medical compounds Nonuse value Existence value Aesthetic value Bequest value Ecological value: keystone species, etc.

  23. Science Focus: Using DNA to Reduce Illegal Killing of Elephants for Their Ivory 1989 international treaty against poaching elephants Poaching on the rise, since the low supply of ivory has made it more valuable Track area of poaching through DNA analysis of elephants Elephants damaging areas of South Africa – especially gardens: Should they be culled? Some evidence suggests that legal elephant hunts lead to increased elephant populaions, since local people protect them as an economic resource

  24. Elephant shot with machine gun, then its face removed with chain saw Stack of confiscated ivory and rhino horn $22,000 ivory cell phone cover

  25. Are We Ethically Obligated to Prevent Premature Extinction? Intrinsic value: existence value Edward O. Wilson: biophilia phenomenon – many people express a love for living things, nature, animals, etc. (bio = life, philia = to love, phobia = to fear) Biophobia

  26. Science Focus: Why Should We Care about Bats? Vulnerable to extinction Slow to reproduce Human destruction of habitats Important ecological roles Feed on crop-damaging nocturnal insects Pollen-eaters Fruit-eaters Unwarranted fears of bats

  27. 9-3 How do Humans Accelerate Species Extinction? Concept 9-3 The greatest threats to any species are (in order) loss or degradation of its habitat, harmful invasive species, human population growth, pollution, climate change, and overexploitation.

  28. HABITAT LOSS, DEGRADATION, AND FRAGMENTATION • Conservation biologists summarize the most important causes of premature extinction as “HIPPCO:” • Habitat destruction, degradation, and fragmentation • Invasive species • Population growth • Pollution • Climate Change • Overharvest

  29. HABITAT LOSS, DEGRADATION, AND FRAGMENTATION • The greatest threat to a species is the loss, degradation, and fragmentation of where it lives. Figure 11-7

  30. Habitatloss Pollution Overfishing Habitat degradation and fragmentation Commercial hunting and poaching Climate change Introducingnonnative species Sale of exotic pets and decorative plants Predator and pest control Secondary Causes • Population growth • Rising resource use • No environmental accounting • Poverty Basic Causes Fig. 11-7, p. 229

  31. HABITAT LOSS, DEGRADATION, AND FRAGMENTATION • Reduction in ranges of four wildlife species, mostly due to habitat loss and overharvest. Figure 11-8

  32. Indian Tiger Range 100 years ago Range today (about 2,300 left) Fig. 11-8a, p. 230

  33. Black Rhino Range in 1700 Range today (about 3,600 left) Fig. 11-8b, p. 230

  34. African Elephant Probable range 1600 Range today Fig. 11-8c, p. 230

  35. Asian or Indian Elephant Former range Range today (34,000–54,000 left) Fig. 11-8d, p. 230

  36. Science Focus: Studying the Effects of Forest Fragmentation on Old-Growth Trees Tropical Biologist Bill Laurance, et al. How large must a forest fragment be in order to prevent the loss of rare trees?

  37. Case Study: A Disturbing Message from the Birds (1) Habitat loss and fragmentation of the birds’ breeding habitats Forests cleared for farms, lumber plantations, roads, and development Intentional or accidental introduction of nonnative species Eat the birds (cats, rats, snakes…) Compete for nest sites Spread diseases (West Nile virus)

  38. Case Study: A Disturbing Message from the Birds (2) Seabirds caught and drown in fishing equipment Migrating birds fly into power lines, communication towers, and skyscrapers Other threats Oil spills Pesticides Herbicides Ingestion of toxic lead shotgun pellets

  39. Case Study: A Disturbing Message from the Birds (3) Greatest new threat: Climate change Environmental indicators: birds are great indicator species, since they are widespread, react quickly to environmental changes, are relatively easy to study, etc. Economic and ecological services

  40. Case Study: A Disturbing Message from the Birds • Human activities are causing serious declines in the populations of many bird species. Figure 11-9

  41. A few endangered US songbirds Black-capped vireo Golden-cheeked warbler Bichnell’s thrush Cerulean warbler Sprague’s pipit Henslow’s sparrow Florida scrub jay California gnatcatcher Bachman’s warbler Kirtland’s warbler Fig. 11-10, p. 232

  42. Case Study: A Disturbing Message from the Birds • The majority of the world’s bird species are found in South America. • Threatened with habitat loss and invasive species. Figure 11-10

  43. Science Focus: Vultures, Wild Dogs, and Rabies: Unexpected Scientific Connections Vultures poisoned from diclofenac in cow carcasses More wild dogs eating the cow carcasses More rabies spreading to people

  44. INVASIVE SPECIES • Many nonnative species provide us with food, medicine, and other benefits but a a few can wipe out native species, disrupt ecosystems, and cause large economic losses. Kudzu vine was introduced in the southeastern U.S. to control erosion. It has taken over native species habitats. Figure 11-A

  45. Some Deliberately Introduced Species Can Disrupt Ecosystems Most species introductions are beneficial Food Shelter Medicine Aesthetic enjoyment However, nonnative species may have no natural Predators Competitors Parasites Pathogens

  46. Case Study: The Kudzu Vine Imported from Japan in the 1930s “ The vine that ate the South:” grew wildly, covering other plants, buildings, etc. with a green blanket Could there be benefits of kudzu?

  47. Case Study: The European Starling Less than 100 starlings brought to Central Park, New York from England by a man who believed that every bird mentioned in Shakespeare should be brought to the New World Millions-billions of starlings now found across the continent Aggressive competitors for nest sites in tree cavities – will kick out other birds and their eggs Many people find them noisy and dirty

  48. Deliberately Introduced Species European starling Purple loosestrife African honeybee (“Killer bee”) Salt cedar (Tamarisk) Nutria Japanese beetle European wild boar (Feral pig) Hydrilla Marine toad (Giant toad) Water hyacinth Fig. 11-11a, p. 234

  49. Some Accidentally Introduced Species Can Also Disrupt Ecosystems Argentina fire ant: 1930s Pesticide spraying in 1950s and 1960s worsened conditions Burmese python – now spreading through the Everglades and displacing native species like alligators Brown tree snake – climbs up in aircraft landing gear, and has spread to new islands in the South Pacific. Has destroyed entire species of birds in Samoa, and Hawaiian officials are very concerned about it getting to the Aloha State.

  50. Accidentally Introduced Species Eurasian ruffe Sea lamprey (attached to lake trout) Argentina fire ant Brown tree snake Common pigeon (Rock dove) Gypsy moth larvae Asian long-horned beetle Asian tiger mosquito Formosan termite Zebra mussel Fig. 11-11b, p. 234

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