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By A Kohn, Marion, WI. 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

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Extinctions: The End of Biodiversity

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By a kohn marion wi

By A Kohn, Marion, WI

Extinctions: The End of Biodiversity

What is extinction

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 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

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 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

Mass Extinction Diagram


Mass extinctions

Mass Extinctions

  • 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)

  • Mass Extinction Recap Video

    (#= millions of years ago)


The holocene extinction

The Holocene Extinction

  • Today’s 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

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 1500times greater than the normal, sustainable extinction rate.

    • BjørnLomborg, 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

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

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

“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

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 extinctions…allows 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

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 Earth’s most biologically rich ecosystems is even worse.

  • There is nothing natural about today’s rate of extinction.


So why care

So why care?

  • Why does this matter?

  • TPS

Biodiversity medicine

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!


Biodiversity agriculture

Biodiversity & Agriculture

  • There are almost 80,000 species of edible plants

  • Fewer than 20 produce 90 percent of the world’s food.

    • 4 crops (wheat, corn, rice, soybeans) provide most of the world’s food.

  • If underutilized species are conserved, they could help to feed growing populations.


Biodiversity crops

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.


Biodiversity ecosystem services

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 free…for now.


Biodiversity moral obligations

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.

  • Can we or should we bring some of these extinct animals back?


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