Locally: a species is no longer found in an area it once inhabited but is still found elsewhere in the world. Ecologically

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Chapter 7

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?

Updates Online

  • The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.
  • InfoTrac: Domestic cats serve as add-on predators. Paducah Sun (Paducah, KY), July 26, 2006.
  • InfoTrac: Invasion of the habitat snatchers. Wichita Eagle, August 6, 2006.
  • InfoTrac: Group pulls for native Denali plants. Anchorage Daily News, June 26, 2006.
  • Union of Concerned Scientists: Invasive Species
  • PBS: Strange Days on Planet Earth
  • USGS: Nonindigenous Aquatic Species

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.


  • 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.

Global Extinction

  • Some animals have become prematurely extinct because of human activities.
  • Aepyornis
  • (Madagascar)
  • Passenger pigeon
  • Great auk
  • Dodo
  • Dusky seaside sparrow

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.
  • Grizzly bear
  • Kirkland’s warbler
  • Knowlton cactus
  • Florida manatee
  • African elephant
  • Utah prairie dog
  • Humpback chub
  • Golden lion tamarin
  • Siberian tiger
  • Hawksbill sea turtle
  • Giant panda
  • Black-footed ferret
  • Whooping crane
  • Northern spotted owl
  • Blue whale
  • Mountain gorilla
  • Florida panther
  • California condor
  • Black rhinoceros


  • Some species have characteristics that make them vulnerable to ecological and biological extinction.
  • Low reproductive rate
  • (K-strategist)
  • Specialized niche
  • Narrow distribution
  • Feeds at high trophic
  • level
  • Fixed migratory patterns
  • Rare
  • Commercially valuable
  • Large territories
  • Characteristic
  • Blue whale, giant panda,
  • rhinoceros
  • Blue whale, giant panda,
  • Everglades kite
  • Many island species,
  • elephant seal, desert pupfish
  • Bengal tiger, bald eagle,
  • grizzly bear
  • Blue whale, whooping crane,
  • sea turtles
  • Many island species,
  • African violet, some orchids
  • Snow leopard, tiger,
  • elephant, rhinoceros,
  • rare plants and birds
  • California condor, grizzly
  • bear, Florida panther
  • Examples


  • 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.


  • Percentage of various species types threatened with premature extinction from human activities.
  • 12%
  • Birds
  • Plants
  • Reptiles
  • Mammals
  • Fish
  • 34% (51% of freshwater species)
  • 25%
  • 20%
  • 14%


  • Scientists use models to estimate the risk of particular species becoming extinct or endangered.
  • 5 million
  • Number of years until one million
  • species are extinct
  • 50,000 extinct per year
  • 14,000 extinct per year
  • Number
  • of species
  • existing
  • Effects of a 0.1% extinction rate
  • 5,000 extinct per year
  • 100 million
  • 50 million
  • 14 million


  • 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).


  • Conservation biologists summarize the most important causes of premature extinction as “HIPPO”:
    • Habitat destruction, degradation, and fragmentation
    • Invasive species
    • Population growth
    • Pollution
    • Overharvest


  • The greatest threat to a species is the loss, degradation, and fragmentation of where it lives.
  • Introducingnonnative species
  • Basic Causes
  • Secondary Causes
  • • Population growth
  • • Rising resource use
  • • No environmental accounting
  • • Poverty
  • Climate change
  • Overfishing
  • Pollution
  • Commercial hunting and poaching
  • Sale of exotic petsand decorative plants
  • Habitatloss
  • Habitat degradation
  • and fragmentation


  • Reduction in ranges of four wildlife species, mostly due to habitat loss and overharvest.
  • Indian Tiger
  • Range today
  • (about 2,300 left)
  • Range in 1700
  • Black Rhino
  • Range today
  • (about 3,600 left)
  • Probable range 1600
  • African Elephant
  • Range today
  • Range today
  • (34,000–54,000 left)
  • Asian or Indian Elephant
  • Former range

Case Study: A Disturbing Message from the Birds

  • Human activities are causing serious declines in the populations of many bird species.
  • Bachman’s warbler
  • Cerulean warbler
  • Sprague’s pipit
  • Bichnell’s thrush
  • Black-capped vireo
  • Golden-cheeked warbler
  • Florida scrub jay
  • California gnatcatcher
  • Kirtland’s warbler
  • Henslow’s sparrow

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.
  • 1
  • 609
  • Number of
  • bird species
  • 400
  • 200


  • 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.


  • Many invasive species have been introduced intentionally.


  • Many invasive species have been introduced unintentionally.
  • Deliberately Introduced Species
  • Purple loosestrife
  • European starling
  • African honeybee
  • (“Killer bee”)
  • Nutria
  • Salt cedar
  • (Tamarisk)
  • European wild boar
  • (Feral pig)
  • Marine toad
  • (Giant toad)
  • Japanese beetle
  • Hydrilla
  • Gypsy moth larvae
  • Accidentally Introduced Species
  • Sea lamprey
  • (attached to lake trout)
  • Argentina fire ant
  • Brown tree snake
  • Eurasian ruffe
  • Common pigeon
  • (Rock dove)
  • Formosan termite
  • Zebra mussel
  • Asian long-horned beetle
  • Asian tiger mosquito


  • The Argentina fire ant was introduced to Mobile, Alabama in 1932 from South America.
    • Most probably from ships.
    • No natural predators.


  • • Do not allow wild animals to escape.
  • • Do not spread wild plants to other areas.
  • • Do not dump the contents of an aquarium into waterways, wetlands, or storm drains.
  • • When camping use wood near your campsite instead of bringing firewood from somewhere else.
  • • Do not dump unused bait into the water.
  • • After dogs visit woods or the water brush them before taking them home.
  • • After each use clean your vehicle, mountain bike, surfboard, kayaks, canoes, boats, tent, hiking boots, and other gear before heading for home.
  • • Empty all water from canoes, kayaks, dive gear, and other outdoor equipment before heading home.
  • • Plant a variety of trees, shrubs, and other plants in your yard to reduce losses from invasive species.
  • • Do not buy plants from overseas or swap them with others using the Internet.
  • What Can You Do?
  • Invasive Species
  • • Climate similar to habitat of invader
  • • Absence of predators on invading species
  • • Early successional
  • systems
  • • Low diversity of native species
  • • Absence of fire
  • • Disturbed by human activities
  • Characteristics of
  • Successful
  • Invader Species
  • Characteristics of
  • Ecosystems Vulnerable
  • to Invader Species


  • Population growth, affluenza, and pollution have promoted the premature extinction of some species.
  • Projected climate change threatens a number of species with premature extinction.


  • Each year pesticides:
    • Kill about 1/5th of the U.S. honeybee colonies.
    • 67 million birds.
    • 6 -14 million fish.
    • Threaten 1/5th of the U.S.’s endangered and threatened species.
  • Example of biomagnification of DDT in an aquatic food chain.
  • DDT in water 0.000003 ppm, or 3 ppt
  • DDT in fish-eating birds (ospreys)
  • 25 ppm
  • DDT in large fish (needle fish)
  • 2 ppm
  • DDT in small fish (minnows)
  • 0.5 ppm
  • DDT in zooplankton 0.04 ppm


  • Some protected species are killed for their valuable parts or are sold live to collectors.
  • Killing predators and pests that bother us or cause economic losses threatens some species with premature extinction.
  • Legal and illegal trade in wildlife species used as pets or for decorative purposes threatens some species with extinction.


  • Rhinoceros are often killed for their horns and sold illegally on the black market for decorative and medicinal purposes.

Case Study: Rising Demand for Bushmeat in Africa

  • Bushmeat hunting has caused the local extinction of many animals in West Africa.
  • Can spread disease such as HIV/AIDS and ebola virus.


  • International treaties have helped reduce the international trade of endangered and threatened species, but enforcement is difficult.
    • One of the most powerful is the 1975 Convention on International Trade of Endangered Species (CITES).
      • Signed by 169 countries, lists 900 species that cannot be commercially traded.

Case Study: The U.S. Endangered Species Act

  • One of the world’s most far-reaching and controversial environmental laws is the 1973 U.S. Endangered Species Act (ESA).
    • ESA forbids federal agencies (besides defense department) to carry out / fund projects that would jeopardize an endangered species.
    • ESA makes it illegal for Americans to engage in commerce associated with or hunt / kill / collect endangered or threatened species.

Case Study: The U.S. Endangered Species Act

  • Biodiversity hotspots in relation to the largest concentrations of rare and potentially endangered species in the U.S.
  • Top Six Hot Spots
  • 1 Hawaii
  • 2 San Francisco Bay area
  • 3 Southern Appalachians
  • 4 Death Valley
  • 5 Southern California
  • 6 Florida Panhandle
  • Concentration of rare species
  • High
  • Low
  • Moderate

Endangered Species

  • Because of scarcity of inspectors, probably no more than 1/10th of the illegal wildlife trade in the U.S. is discovered.

Endangered Species

  • Congress has amended the ESA to help landowners protect species on their land.
  • Some believe that the ESA should be weakened or repealed while others believe it should be strengthened and modified to focus on protecting ecosystems.
  • Many scientists believe that we should focus on protecting and sustaining biodiversity and ecosystem function as the best way to protect species.

How Would You Vote?

  • To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
  • Should the Endangered Species Act be modified to protect and sustain the nation's overall biodiversity?
    • a. No. Protecting entire habitats will only further interfere with the rights of landowners.
    • b. Yes. Protecting endangered habitats is more efficient and effective than saving individual species.


  • The U.S. has set aside 544 federal refuges for wildlife, but many refuges are suffering from environmental degradation.
  • Pelican Island was the nation’s first wildlife refuge.


  • Gene banks, botanical gardens and using farms to raise threatened species can help prevent extinction, but these options lack funding and storage space.
  • Zoos and aquariums can help protect endangered animal species by preserving some individuals with the long-term goal of reintroduction, but suffer from lack of space and money.


  • Reconciliation ecology involves finding ways to share places we dominate with other species.
    • Replacing monoculture grasses with native species.
    • Maintaining habitats for insect eating bats can keep down unwanted insects.
    • Reduction and elimination of pesticides to protect non-target organisms (such as vital insect pollinators).

Using Reconciliation Ecology to Protect Bluebirds

  • Putting up bluebird boxes with holes too small for (nonnative) competitors in areas where trees have been cut down have helped reestablish populations.
  • • Do not buy furs, ivory products, and other materials made from endangered or threatened animal species.
  • • Do not buy wood and paper products produced by cutting remaining old-growth forests in the tropics.
  • • Do not buy birds, snakes, turtles, tropical fish, and other animals that are taken from the wild.
  • • Do not buy orchids, cacti, and other plants that are taken from the wild.
  • • Spread the word. Talk to your friends and relatives about this problem and what they can do about it.
  • What Can You Do?
  • Protecting Species

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