Transcript 4.2_Causes of Extinction

Extinction and threats to biodiversity
 Two major causes
 Natural Causes (Non-Human)
 Human Causes
 Volcanic Eruptions
 Drought
 Meteors
 Glaciers and ice age
 Competition and Predation
 H-Habitat destruction and
fragmentation
 I- Introduced species
 P-Pollution
 P-Practices of agriculture
 O-Over hunting
Dodo Bird – Extinct
 Degradation: reducing the quality of available habitat
 Ex. Logging, agriculture, sewage
 Fragmentation: splitting a single large, contiguous
system into many disconnected areas
 Ex. Putting a road through a wilderness area, or building a
dam across a river
 Loss: Disappearing of an entire habitat
 Ex. Paving natural area for building sites, converting
prairies to farmland or residential subdivisions
 Organisms that are living in an environment outside of
its normal range or natural environment
 Many are transported by accident
 Biocontrol: Species transported intentionally to control
other “problem” species populations
 Characteristics:
 Fast growth/reproduction
 Live in wide range of environments
 Usually harmful to environment
 Outcompete native organisms for local food sources
 Leads to extinction of native organisms
 Asian Carp
 Kudzu
 Rabbits
 Starlings
 Cane Toads
 “the vine that ate the
South” and “The Green
Menace”.
 Grow up to 1 foot in a
day!
 Introduced from Japan as
quick ground cover to
prevent soil erosion
Asian Carp
 Originally imported to clear algae from catfish ponds
in the southern USA,
 Flooding allowed some carp to escape into the
Mississippi River and its tributaries where they quickly
became MANY carp
 Pose a strong threat to the Great Lakes
 Asian Carp Research
 “The introduction of a
few rabbits could do
little harm and might
provide a touch of
home, in addition to a
spot of hunting.”
-Thomas Austin in 1859
(Released 24 rabbits)
 1950 ~ 600 million
rabbits
 1951 ~ 100 million
Government Drugged Watering Hole
 Today starlings are blamed for agricultural losses of up
to $800 million annually in the United States, as well
as being implicated in a number of deadly plane
crashes.
 ~ 60 were released in New York’s Central Park in 1890.
 Good Example of biocontrol!
 In 1937 cane toads were released in Australia's sugar
cane plantations to control insect populations
 By 1938 ~60,000 cane toads left sugar cane fields for
more natural habitat (ate all majority of insect
populations and outcompeted native amphibians for
food)
 Can grow up to 15 inches and eat anything!
 Toxins added to the environment lead to a loss or
degradation of habitat.
 Farming causes habitat loss and reduces
biodiversity because of…
 Monoculture: Farming of only one crop on a large scale
 Pesticides: Often lethal to many non-pest species
 Herbicides: Lethal to species other than the weeds
 Collecting, and harvesting wild
populations: unregulated, it can
diminish local populations or even
drive some to extinction
 Tasmanian tiger
 dodo
 North American sea mink
 Prairie buffalo
 Blue whale
 OVERFISHING IS HUGE PROBLEM TODAY!
 CURRENT RATE OF CATCH IS UNSUSTAINABLE
 Fossil Records reveal average “lifetimes” of species.
 Extinction occurs naturally and is referred to as the
background rate of extinction
 Humans have lead to a 1000x extinction rate
 Estimated 137 species lost each day
 50,000 species a year
 The Earth has experienced 5 mass extinctions
 Extinction # 1 ~445 MYA Ordovician Stage – Dramatic
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loss of sea level due to forming Antarctica -57% Extinct
Extinction # 2 ~ 370 MYA Devonian Stage – Changes in
sea level and global cooling stage -50% Extinct
Extinction #3 ~250 MYA Permian Stage- Breaking up of
Pangea changed ocean currents- 83% Extinction
Extinction #4 ~200 MYA Triassic Stage – Climate
warming from volcanic eruptions -48% Extinct
Extinction #5 ~65 MYA Cretaceous – Asteroid impacting
the earth – 50% Extinct
 Mammals: ~ 1 million years
 With approximately 5,000
mammals the background rate
is 1 every 200 years
 In past 400 years 89 extinctions
have been recorded.
 45x background rate.
 Over 50 extinctions have
occurred in the past century
 100x background rate
 Organisms that are…
 Limited habitat
 Extremely specialized niche
 Low reproductive potential
 Require a large territory
 Migratory
 Valuable economically (hunted)
 Vulnerable to pollution
 Incompatible with civilization
 may be more likely to go extinct
 Contain 50% of Earth’s known
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species
Most species have specialized niches
Humans disrupt environment for
logging
Changing one part of ecosystem
alters the entire web of relationships
Breakdown of rainforest likely lead to
extinction of 10% worlds species in 25
years
Regeneration rate is slow due to poor
soil quality (rapid year round
nutrient cycling depletes soil)
 IUCN (International Union for Conservation of
Nature)
 Red list used to determine extinction risk
 Specific Aims:
 Provide system that can be applied consistently
 Improve evaluation of different factors which affect the
risk of extinction
 Population size:
 How many of this species exist?
 Reduction in population size:
 How fast is population decreasing?
 Numbers of mature individuals:
 These are past their reproductive years and may lead to further
decline
 Geographic range and fragmentation:
 Wide range makes the species less likely to be
threatened
 Fragmented habitat reduces interbreeding populations
 Quality of habitat:
 Degraded habitat supports fewer individuals
 Extinct (Ex) – No reasonable doubt that the last
individual has died. Determined after exhaustive
surveys of animals known range and expected habitats
 Endangered (E)- Survival is unlikely if causal factors
continue operating. Drastically reduced populations
and habitat
 Vulnerable (V) – Near endangered if causal factors
continue. Numbers are abundant but are under threat
from serious factors (overexploitation, habitat
destruction)
 Rare (R) – Small world populations that are at risk.
Unexpected threat could easily cause a critical decline
(small geographic disturbance)
 Unknown (K) – Suspected to fit in one of the above
categories but there is a lack of information