Chapter 12 Sustaining Biodiversity: The Species Approach
SPECIES EXTINCTION • Species can become extinct: • ________: 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 _______role. • Globally (____________): Species is no longer found on the earth.
Chapter Overview Questions • How do biologists estimate extinction rates, and how do human activities affect these rates? • Why should we care about biodiversity and species extinction? • 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?
Core Case Study: The Passenger Pigeon - Gone Forever • Once the most numerous bird on earth. • In _______, Passenger Pigeon hunting became a big business. • By 1900 they became ______ from over-harvest and _______ _____. Figure 12-1
Global Extinction • Some animals have become prematurely extinct because of human activities. Figure 12-2
Aepyornis (Madagascar) Passenger pigeon Great auk Dodo Dusky seaside sparrow Fig. 12-2, p. 225
Endangered and Threatened Species: Ecological Smoke Alarms • Endangered species: so few ________ _____ that it could soon become ________. • ___________ _________: still abundant in its natural range but is likely to _______ ________ in the near future. Figure 12-3
Florida manatee Kirkland’s warbler Grizzly bear Knowlton cactus African elephant Swallowtail butterfly Humpback chub Utah prairie dog Siberian tiger Golden lion tamarin Fig. 12-3, p. 226
Giant panda Blue whale Whooping crane Northern spotted owl Black-footed ferret Mountain gorilla Florida panther California condor Hawksbill sea turtle Black rhinoceros Fig. 12-3, p. 227
SPECIES EXTINCTION • Some species have characteristics that make them vulnerable to ecological and biological extinction. • R-strategists: • K-strategists: Figure 12-4
Reproductive Patterns • r-selected species tend to be opportunists while K-selected species tend to be competitors. Figure 9-10
Characteristic Examples 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 Low reproductive rate (K-strategist) Specialized niche Narrow distribution Feeds at high trophic level Fixed migratory patterns Rare Commercially valuable Large territories Fig. 12-4, p. 228
SPECIES EXTINCTION • Scientists use measurements and _______ to estimate ____________ rates. • The International Union for the ___________ of Nature and Natural Resources (IUCN) publishes an annual______ _____, listing the world’s threatened species. • The 2004 Red List contains __________ species at risk for extinction.
SPECIES EXTINCTION • Percentage of various species types threatened with premature extinction from human activities. Figure 12-5
34% (51% of freshwater species) Fish 25% Mammals 20% Reptiles 14% Plants 12% Birds Fig. 12-5, p. 228
SPECIES EXTINCTION • Scientists use models to estimate the risk of particular species becoming extinct or endangered.
Number of species existing Effects of a 0.1% extinction rate 5,000 extinct per year 5 million 14 million 14,000 extinct per year 50 million 50,000 extinct per year 100 million 100,000 extinct per year Number of years until one million species are extinct
IMPORTANCE OF WILD SPECIES • We should not cause the premature extinction of species because of the _________ and ________ services they provide. • Some believe that each wild species has an _________ right to exist. • Some people distinguish between the survival rights among various types of species (plants vs. animals).
HABITAT LOSS, DEGRADATION, AND FRAGMENTATION • Conservation biologists summarize the most important causes of premature extinction as “_____”: • Habitat destruction, degradation, and ___________ • Invasive species • Population growth • Pollution • Overharvest
HABITAT LOSS, DEGRADATION, AND FRAGMENTATION • The greatest threat to a species is the loss, degradation, and fragmentation of where it lives. Figure 12-6
Habitatloss Pollution Overfishing Habitat degradation and fragmentation Commercial hunting and poaching Climate change Introducingnonnative species Sale of exotic petsand decorative plants Predator and pest control Secondary Causes • Population growth • Rising resource use • No environmental accounting • Poverty Basic Causes Fig. 12-6, p. 231
HABITAT LOSS, DEGRADATION, AND FRAGMENTATION • Reduction in ranges of four wildlife species, mostly due to habitat loss and overharvest. Figure 12-7
Indian Tiger Range 100 years ago Range today (about 2,300 left) Fig. 12-7a, p. 232
Black Rhino Range in 1700 Range today (about 3,600 left) Fig. 12-7b, p. 232
African Elephant Probable range 1600 Range today Fig. 12-7c, p. 232
Asian or Indian Elephant Former range Range today (34,000–54,000 left) Fig. 12-7d, p. 232
Case Study: A Disturbing Message from the Birds • Human activities are causing serious declines in the populations of many bird species. Figure 12-8
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. 12-8, p. 233
Case Study: A Disturbing Message from the Birds • The majority of the world’s bird species are found in South America. • Threatened with __________loss and _________species.
Number of bird species 609 400 200 1
INVASIVE SPECIES • Many ________species provide us with food, medicine, and other benefits but a few can wipe out _______ ______, disrupt ________, 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 12-10
INVASIVE SPECIES • Many invasive species have been introduced intentionally. Figure 12-9
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. 12-9a, p. 235
INVASIVE SPECIES • Many invasive species have been introduced unintentionally. Figure 12-9
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. 12-9b, p. 235
INVASIVE SPECIES • The Argentina fire ant was introduced to Mobile, Alabama in 1932 from South America. • Most probably from ships. • No natural predators.
INVASIVE SPECIES • _________is the best way to reduce threats from invasive species, because once they arrive it is almost ________ to slow their spread.
Characteristics of Successful Invader Species Characteristics of Ecosystems Vulnerable to Invader Species • High reproductive rate, short generation time (r-selected species) • Pioneer species • Long lived • High dispersal rate • Release growth-inhibiting chemicals into soil • Generalists • High genetic variability • 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 Fig. 12-12, p. 238
POPULATION GROWTH, POLLUTION, AND CLIMATE CHANGE • Population growth, _________, and pollution have promoted the premature _________ of some species. • Projected ________ _______threatens a number of species with premature extinction.
Pollution • 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 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 DDT in water 0.000003 ppm, or 3 ppt
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.
OVEREXPLOITATION • Rhinoceros are often killed for their horns and sold ________ on the ______ ______ 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 ______ ____. Figure 12-13
PROTECTING WILD SPECIES: LEGAL AND ECONOMIC APPROACHES • International treaties have helped reduce the _____________ ______of endangered and threatened species, but enforcement is difficult. • One of the most powerful is the 1975 Convention on International Trade of Endangered Species (______). • 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. __________ ________ ___ (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 _____ / kill / _______ 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. Figure 12-14
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 Moderate Low High Fig. 12-14, p. 242