EXTINCTIONS: THE
END OF
BIODIVERSITY
What is extinction?
Extinctions occur when the last
individual of a species dies out.
Functional Extinctions occur when
individuals remain but the odds of
sustainable reproduction are low
i.e. the species is effectively extinct even
though individuals remain.
The passenger pigeon
The last passenger pigeon in
Wisconsin was shot at Babcock,
in September, 1899. This is reportedly the last
passenger pigeon shot in the wild.
The last Passenger Pigeon, named Martha, died
alone at the Cincinnati Zoo at about 1:00 pm on
September 1, 1914.
Within a few decades, the once most-numerous bird on
Earth would be forever gone.
Even when Martha was still alive, the species was
already functionally extinct it would never return to
a sustainable population.
When do extinctions
occur?
Extinctions occur when the environment of a
species changes faster than the species can
adapt.
In other words, a species adaptations are no longer
sufficient in allowing that species to acquire and
compete for resources.
Extinctions can be local, widespread, or global.
For example, the timber wolf was until recently
extinct in Wisconsin but not in Minnesota
Wild elk and woodland caribou are now extinct in
Wisconsin but may be found on game farms.
Extinctions are natural.
Extinctions occur naturally.
Nearly all of the species that have
existed on earth have gone extinct.
There have been 5 major mass
extinctions in geological history.
Recovery from these events took
millions of years.
Mass Extinction Diagram
Source: http://www.uwec.edu/jolhm/EH4/Extinction/Extinction.ppt
Mass Extinctions
1.
2.
3.
4.
5.
6.
Cretaceous-Tertiary Extinction (65 mya).
End Triassic Extinction (200).
Permian Triassic Extinction (250).
Late Devonian Extinction (364).
Ordovician-Silurian Extinction (440).
Holocene Extinction (0 mya)
(#= millions of years ago)
Source:
http://www.uwec.edu/jolhm/EH4/Extinction/Extinction.
ppt
The Holocene Extinction
Todays massive loss of species has been dubbed the
Holocene Extinction (we are currently in the Holocene
epoch)
Epoch: a portion of a geological period
Catastrophic extinctions, as was the case when an
asteroid-strike wiped out the dinosaurs, actually took many
thousands of years to occur.
The current extinction rate appears significantly greater.
In other words, human-activity is killing off species faster than an
asteroid could 65 million years ago.
Source: United States Committee on Scientific Issues in the
Endangered Species Act, National Research Council. Science and
the Endangered Species Act. National Academy Press,
Washington D.C. 1995
Current Stats
90% of all large fish have disappeared in the last 50 years due to over-fishing.
Myers, Ransom. Worm, Boris. Biology Department, Dalhousie University, Halifax, Nova Scotia, Canada, Rapid Worldwide Depletion of
Predatory Fish Communities. Nature. Volume 423. P. 280. May 2003
The Audubon Society reports that 30% of North American songbird species are
in significant decline.
One in eight plant species are in danger of extinction within the next 30 years
(ICUN Red List)
The current rate of extinction is 1500 times greater than the normal, sustainable
extinction rate.
Bjrn Lomborg, The Skeptical Environmentalist: Measuring the Real State of the World, Cambridge U. Press, Cambridge, 2001.
Half of bird and mammal species will be gone in 200 to 300 years
Levin, Phillip and Levin, Donald. The Real Biodiversity Crisis. January, 2002. American Scientist, Volume 90, Number 1,
Page 6
One species is going extinct every 20 minutes.
Levin, Phillip and Levin, Donald. The Real Biodiversity Crisis. January, 2002. American Scientist, Volume 90, Number 1,
Page 6
Modern Causes of
Extinctions
Major current causes of extinctions include:
Habitat Loss: fragmentation, degradation, and
outright destruction of ecosystems that support
native ecosystems (leading cause).
Invasive Species: the introduction or overpopulation
of species that over-consume natural resources and
are uncontrolled by predators (second leading
cause).
Over-harvesting: the removal of species at rates that
exceed reproduction
Pollution: introduction of harmful agents that reduce
the effectiveness of a species adaptations
The 4 Horsemen of
Extinction
These main four causes of
extinction can be thought of
as the Four Horsemen of
Extinction.
Much like the biblical
horsemen of the
apocalypse, these four
factors have decimated
populations of living species
across the planet.
Profound Loss of Biodiversity
Information on the rate of species
introduction and the nature of the impacts of
introduced species on native species and
ecosystems allows inferences about
extinction rates.
The evidence all points to a global tragedy
with a profound loss of biodiversity.
Daniel Simberloff, professor of environmental
studies and director of the Institute for Biological
Invasions at the University of Tennessee
For the birds
Of about 6 to 10 million currently existing
species, we have still only identified 1 million.
For groups that we know well, knowledge of
very recent species extinctionsallows us to be
certain that extinction rates are comparable
to those of the great past extinctions.
For birds, of about 10,000 species worldwide
at least 128 have disappeared in the last 500 years
about 1,200 are currently seriously threatened with
extinction (all but three from human activities)
Daniel Simberloff
Since Plymouth Rock
Biologists estimate that since the Pilgrims
landed at Plymouth Rock in 1620, more than
500 species, subspecies, and varieties of
our US plants and animals have become
extinct.
The situation in Earths most biologically rich
ecosystems is even worse.
There is nothing natural about todays rate of
extinction.
http://www.fws.gov/endangered/esa-library/pdf/Why_Save_End
angered_Species_Brochure.pdf
So why care?
Why does this matter?
TPS
Biodiversity & Medicine
More than a quarter of all prescriptions
written annually in the United States contain
chemicals discovered in plants and animals.
A few hundred wild species have stocked
our pharmacies with antibiotics, anti-cancer
agents, pain killers, and blood thinners.
We have only discovered 10-20% of living
species so far!
http://www.fws.gov/endangered/esa-library/pdf/Why_Save_Endangered_Species_Br
ochure.pdf
Biodiversity &
Agriculture
There are almost 80,000 species of edible
plants
Fewer than 20 produce 90 percent of the
worlds food.
4 crops (wheat, corn, rice, soybeans) provide
most of the worlds food.
If underutilized species are conserved, they
could help to feed growing populations.
http://www.fws.gov/endangered/esa-library/pdf/Why_Save_Endangered_Species_B
rochure.pdf
Biodiversity & Crops
During the 1970s the U.S. corn crop was almost
completely wiped out by a leaf fungus.
The corn crop was saved by interbreeding it with
a rare species of wild corn from Mexico.
Genetic engineering may also offer some hope
by facilitating transfer of genes between species.
This increases the value of wild strains which can be
used as sources for new traits to be introduced into
crops.
http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookcycle
s.html
Biodiversity & Ecosystem
Services
Ecosystem services include air and water
purification, detoxification and decomposition of
wastes, climate regulation, regeneration of soil
fertility, and the production and maintenance of
biological diversity.
These are the key ingredients of our agricultural,
pharmaceutical, and industrial enterprises.
Such services are estimated to be worth trillions
of dollars annually.
We get these services for freefor now.
http://www.fws.gov/endangered/esa-library/pdf/Why_Save_Endan
gered_Species_Brochure.pdf
Biodiversity & Moral Obligations
Would our descendants forgive us for
exterminating a unique form of life?
Eliminating entire species has been
compared to ripping pages out of books
that have not yet been read.
http://www.fws.gov/endangered/esa-library/pdf/Why_
Save_Endangered_Species_Brochure.pdf
