Transcript 112903_Causes_of_Spp_Extinction

Current Leading Causes of
Species Extinction
Holocene Extinction Event

???
Holocene Extinction Event
6th mass extinction
 Some natural causes such as
deglaciation, natural climatic shifts,
natural rate of extinction
 Main cause is….

Holocene Extinction Event
6th mass extinction
 Some natural causes such as
deglaciation, natural climatic shifts,
natural rate of extinction
 Main cause is humans.

 HOW?
Invasive (introduced) Species
Invasive (introduced) Species

Due to their lack of natural predators
and the fact that native species are not
adapted to their competition, invasive
species are often very successful
Invasive (introduced) Species
Housecats???

84 million in U.S.
 New data suggests
they kill 2.9 billion
birds and 12.5 billion
mammals per year

http://theoatmeal.co
m/comics/cats_actu
ally_kill
Habitat Destruction

85% of old growth forest in U.S. is gone. (some 2nd
growth, some other uses)
Habitat Fragmentation

Breaking large
ecosystems into
smaller ones can
lead to extinction.
 Smaller islands of
habitats can lead to:

Loss of genetic
diversity (inbreeding)
 Inadequate food
supplies for large
animals
Overexploitation
Pollution?



Not a major driver of
extinction on land
Main pollution problem
in water is
eutrophication – too
many nutrients running
into ocean (mainly from
agricultural run-off)
Overloaded nutrients
cause algae blooms,
which cause dead
zones in the water due
to oxygen deprivation
Guns + Animals = Good???

In U.S., money from every hunting license
goes to buy wetlands -> Habitat Preservation
 Over $500 million annually, leading to
hundreds of thousands of acres of habitat
protected in past few decades

In Africa, most funds for wildlife protection
comes from hunting fees
So, how are we doing?

Since 1972, we’ve delisted (saved) 28
species (25 additional
species have been
down-listed from
endangered to
threatened

Currently have 1,162
species on the
Endangered Species
List in U.S.