biodiversity in perspective chapter 27. easter island 165 km 2 island in polynesia 165 km 2 island...
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Biodiversity in Biodiversity in PerspectivePerspective
Chapter 27Chapter 27
Easter IslandEaster Island
165 km165 km22 island in Polynesia island in Polynesia
Hundreds of massive stone statuesHundreds of massive stone statues
When Europeans first visited in 1722, When Europeans first visited in 1722,
the population was small and there the population was small and there
was little vegetationwas little vegetation
Easter Island HistoryEaster Island History
Colonized around 350 A.D.Colonized around 350 A.D.
Island was fertile and densely forestedIsland was fertile and densely forested
By 1400, soil fertility and crop yields By 1400, soil fertility and crop yields
had declinedhad declined
By 1550, the forests were all goneBy 1550, the forests were all gone
Food scarcity led to warfareFood scarcity led to warfare
Loss of BiodiversityLoss of Biodiversity
On Easter Island, 15,000 people nearly On Easter Island, 15,000 people nearly totally destroyed the biodiversity upon totally destroyed the biodiversity upon which they dependedwhich they depended
Today, there are six billion people on Today, there are six billion people on Earth and global biodiversity is Earth and global biodiversity is decliningdeclining
A worldwide extinction crisis is in the A worldwide extinction crisis is in the makingmaking
Biodiversity & ExtinctionBiodiversity & Extinction
90 percent of all species that have 90 percent of all species that have
ever lived are now extinctever lived are now extinct
Biodiversity is greater than everBiodiversity is greater than ever
Current range of biodiversity is the Current range of biodiversity is the
result of past extinctions and result of past extinctions and
recoveriesrecoveries
Mass ExtinctionsMass Extinctions
There have been five great mass There have been five great mass
extinctionsextinctions
Causes of mass extinctions are not Causes of mass extinctions are not
always clearalways clear
– Asteroid hit Earth at the K-T boundary, Asteroid hit Earth at the K-T boundary,
but many species were already in but many species were already in
declinedecline
Slow RecoveriesSlow Recoveries
Each mass extinction has been followed by Each mass extinction has been followed by
an adaptive radiationan adaptive radiation
Biodiversity recovers very slowlyBiodiversity recovers very slowly
It takes 20 million to 100 million years to It takes 20 million to 100 million years to
reach the pre-mass extinction level of reach the pre-mass extinction level of
diversitydiversity
Patterns in Some LineagesPatterns in Some Lineages
CENOZOIC
MESOZOIC
PALEOZOIC
CENOZOIC
MESOZOIC
PALEOZOIC
PROTOZOANS TRILOBITESBONY FISHES AMPHIBIANS REPTILES BIRDS MAMMALS
GYMNOSPERMSANGIOSPERMS (flowering plants)
INSECTS
(mammalian diversity for ten families studied)
Figure 27.2Page 476
Dead as a DodoDead as a Dodo Flightless bird lived on the island of Flightless bird lived on the island of
MauritiusMauritius
Killed off by EuropeansKilled off by Europeans
Once the dodo was extinct, a native Once the dodo was extinct, a native tree stopped reproducingtree stopped reproducing
May have coevolved with dodoMay have coevolved with dodo
Humans and Humans and Mammalian DiversityMammalian Diversity
Humans began hunting mammals Humans began hunting mammals
about 2 million years agoabout 2 million years ago
About 11,000 years ago, they began to About 11,000 years ago, they began to
drastically reduce mammalian habitatdrastically reduce mammalian habitat
Of the 4,500 living mammal species, Of the 4,500 living mammal species,
300 (6.7 percent) are endangered300 (6.7 percent) are endangered
Endangered SpeciesEndangered Species
An endemic species that is An endemic species that is
extremely vulnerable to extinctionextremely vulnerable to extinction
– EndemicEndemic means a species originated means a species originated
in one geographic region and is in one geographic region and is
found nowhere elsefound nowhere else
Threatened RegionsThreatened Regions
Critically endangered species
Threatened species
Relatively stable species; populations intact
Figure 27.4Page 478
Habitat LossHabitat Loss
Physical reduction of suitable places to Physical reduction of suitable places to
live, as well as loss of habitat as a live, as well as loss of habitat as a
result of chemical pollutionresult of chemical pollution
In the U.S.:In the U.S.:
– 98 percent of tallgrass prairies are gone98 percent of tallgrass prairies are gone
– 50 percent of wetlands have been 50 percent of wetlands have been
destroyeddestroyed
Habitat FragmentationHabitat Fragmentation
Habitats are chopped up into patchesHabitats are chopped up into patches Three effects:Three effects:
– Increases habitat edgesIncreases habitat edges– Decreases number of individuals that Decreases number of individuals that
can be supported; may be too few to can be supported; may be too few to allow breedingallow breeding
– Decreases the area in which individuals Decreases the area in which individuals can find food or other resourcescan find food or other resources
Island BiogeographyIsland Biogeography
Study of the factors affecting Study of the factors affecting
diversity on islandsdiversity on islands
Has implications for predicting Has implications for predicting
extinction of nonisland speciesextinction of nonisland species
Isolated patches of habitat are like Isolated patches of habitat are like
islandsislands
MacArthur-Wilson ModelMacArthur-Wilson Model
Uses island biogeography to Uses island biogeography to estimate future extinctionsestimate future extinctions
Model predictsModel predicts– Destruction of 50 percent of a habitat Destruction of 50 percent of a habitat
island will drive 10 percent of endemic island will drive 10 percent of endemic species to extinctionspecies to extinction
– Destruction of 90 percent of a habitat Destruction of 90 percent of a habitat island will drive 50 percent of species island will drive 50 percent of species to extinctionto extinction
Indicator SpeciesIndicator Species
Species that provide warning of Species that provide warning of changes in habitat and impending changes in habitat and impending widespread loss of biodiversitywidespread loss of biodiversity
Example:Example:– Migratory birds that breed in N. America Migratory birds that breed in N. America
and winter over in tropical forestsand winter over in tropical forests– Study found populations are plummeting as Study found populations are plummeting as
a result of deforestation, habitat a result of deforestation, habitat fragmentationfragmentation
Exotic SpeciesExotic Species
Species that have been introduced into Species that have been introduced into a habitat, either deliberately or a habitat, either deliberately or accidentallyaccidentally
Exotic species often have characteristics Exotic species often have characteristics that allow them to outcompete endemic that allow them to outcompete endemic speciesspecies
Play a role in 70 percent of cases where Play a role in 70 percent of cases where endemic species are threatenedendemic species are threatened
Hunting and WhalesHunting and Whales
humpback whale
sperm whale
sei whale
fin whale
blue whale
other species
Figure 27.6Page 479
Distribution of Coral ReefsDistribution of Coral Reefs
Coral reefs
Localities for solitary corals
Deep-water coral banks or thickets
Restricted 21°C (70°F) isotherm Figure 27.7Page 480
Threats to Coral ReefsThreats to Coral Reefs
Natural threats, such as hurricanesNatural threats, such as hurricanes
Man-made threatsMan-made threats– Water pollution, oil spillsWater pollution, oil spills
– Dredging Dredging
– Dynamite and cyanide fishingDynamite and cyanide fishing
– Coral bleachingCoral bleaching
Coral BleachingCoral Bleaching
Reef-building corals have photosynthetic, Reef-building corals have photosynthetic,
dinoflagellate symbiontsdinoflagellate symbionts
When stressed, corals expel the protistansWhen stressed, corals expel the protistans
If the stress persists, the coral dies, If the stress persists, the coral dies,
leaving its bleached hard parts behindleaving its bleached hard parts behind
Coral bleaching may be an effect of global Coral bleaching may be an effect of global
warming and increased sea temperatureswarming and increased sea temperatures
Rachel CarsonRachel Carson
Oceanographer and marine biologistOceanographer and marine biologist
Published Published Silent SpringSilent Spring in 1962 in 1962
– Described the harmful effects of Described the harmful effects of
pesticides on songbirds and other pesticides on songbirds and other
speciesspecies
Book helped launch the Book helped launch the
environmental movementenvironmental movement
Conservation BiologyConservation Biology
Systematic study of biodiversitySystematic study of biodiversity
Works to elucidate the evolutionary Works to elucidate the evolutionary
and ecological origins of biodiversityand ecological origins of biodiversity
Attempts to identify ways to maintain Attempts to identify ways to maintain
biodiversity for the good of human biodiversity for the good of human
populationspopulations
Identifying Hot SpotsIdentifying Hot Spots
A global survey of biodiversity is A global survey of biodiversity is impossibleimpossible
Researchers are identifying habitats Researchers are identifying habitats where many endemic species are where many endemic species are facing extinction facing extinction
Regional data is pooled to create a Regional data is pooled to create a global inventory of biodiversityglobal inventory of biodiversity
What’s It Worth?What’s It Worth?
Economic analysis can assign future Economic analysis can assign future value to ecoregionsvalue to ecoregions
Successful conservation requires that Successful conservation requires that sustaining biodiversity have greater sustaining biodiversity have greater economic value than destructioneconomic value than destruction
Biodiversity may have future Biodiversity may have future economic value as a source of economic value as a source of medications or chemical products medications or chemical products
People versus BiodiversityPeople versus Biodiversity The main threat to biodiversity is The main threat to biodiversity is
growth of human populations growth of human populations Many poor people must now choose Many poor people must now choose
between the good of endangered between the good of endangered species and the good of their families species and the good of their families
People will sustain biodiversity when People will sustain biodiversity when they can make a living by doing sothey can make a living by doing so
Strip LoggingStrip Logging
Allows tropical woods to be logged in Allows tropical woods to be logged in a profitable, sustainable waya profitable, sustainable way
Sloped forested area is logged in Sloped forested area is logged in strips, working up the slopestrips, working up the slope
Runoff from logged areas flows to Runoff from logged areas flows to regenerating forest, enhancing its regenerating forest, enhancing its growthgrowth
Strip LoggingStrip Logging
uncut forest
cut 1 year agodirt road
cut 3-5 years ago
cut 6-10 years ago
uncut forest
stream
Figure 27.12Page 484
Riparian ZonesRiparian Zones
Narrow corridors of vegetation along Narrow corridors of vegetation along streams or riversstreams or rivers
Rich in endemic speciesRich in endemic species In the American West, cattle have In the American West, cattle have
destroyed most riparian vegetationdestroyed most riparian vegetation Rotating cattle away from riparian Rotating cattle away from riparian
zones saves endemic species and zones saves endemic species and provides richer grazingprovides richer grazing
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