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Anthropogenic Mass Extinction. Homo sapiens and the Evolution of the Biosphere since the Pleistocene. Kyle Burchett University of Kentucky. Mass Extinctions of the Past. → Unavoidable Prolonged Geologic Events. Cosmic Collisions. Mass extinctions are normal events for Earth’s life forms.

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Anthropogenic mass extinction

Anthropogenic Mass Extinction

Homosapiens and the Evolution of the Biosphere since the Pleistocene

Kyle Burchett

University of Kentucky


Mass extinctions of the past
Mass Extinctions of the Past

→Unavoidable

Prolonged Geologic Events




The fittest of the fittest
The Fittest of the Fittest

  • Microscopic organisms such as bacteria show up in the fossil record for at least four billion years.

  • They are virtually indestructible and immune to the mass extinction events which regularly befall more ‘complex’ species.


An objective view of mass extinction
An Objective View of Mass Extinction

“In a sense we are like fruit flies, which live but a few weeks and cannot experience most seasonal changes, much less a year. We cannot know from experience the history of planet Earth. Most of it is destined to be as abstract to a layperson as the dimensions of the universe” (Martin 2005:54).


The Pleistocene Puzzle

  • Approximately 50,000 years ago, the Earth’s megafauna began to exhibit an unusual extinction pattern.

    • Almost exclusively largeanimals – megafauna – rapidly began to disappear around the world.

    • 65%of mammal genera whose members weighed morethan97pounds were utterly extirpated.

    • 97of150genera of megafaunabecame extinct.

    • Plantsand marinelife were largely unaffected.

  • Previous mass extinctions evenly affected all types of organisms, including animals of all sizes, plants, and marine life.

  • (Barnosky et al. 2004; Lyons et al. 2004; Martin 2005; Nogués-Bravo et al. 2010)


  • Three compelling hypotheses
    Three Compelling Hypotheses

    • Climate Change

      (Generally construed as non-anthropogenic)

    • Overkill

      Anthropogenic

    • Hyperdisease

      Anthropogenic or otherwise


    Climate change
    Climate Change

    (Nogués-Bravo et al. 2010:2444)


    Extreme climate changes radically alter the possible biotic composition of ecosystems.

    (Delcourt and Delcourt 2004)

    Extinction may be the only possible response for some species.

    Competition for limited available resources increases drastically both within and across species.

    If access points to alternate habitats are cut off, migration is not an option.

    (Boulter 2002:119)


    Climate change alone however is insufficient
    Climate change alone, however, is insufficient. . . composition of ecosystems.

    • Climate-induced mass extinctions should not show discrimination for large body size or exclude plant and marine life.

    • 20 glacial-interglacial periods / 2 million years

      • A mass extinction pulse only shows up at the end of the Pleistocene (andcontinuestoday).

        • 50% of plant and marine life are currently threatened with extinction.

    (Boulter 2002:51)


    Invasion overkill extinction
    Invasion → Overkill → Extinction composition of ecosystems.

    b

    (Martin 2005:7)


    A smoking spear
    A Smoking Spear? composition of ecosystems.

    • 76 North American Clovis sites reviewed

      • 14 contained extinct megafaunal remains

        • 12 – mammoths

        • 2 – mastodons

          (Grayson and Meltzer 2002)


    Mass extinction inevitable – even with moderate human population growth and hunting practices(Alroy 2001:1895)


    Buffalo jumps
    Buffalo Jumps population growth and hunting practices

    • Entire herds driven over cliffs

      (Burroughs 2005:187)

      • Bone layers as deep as 20 feet

    • Historical mass killing of megafauna


    The passenger pigeon
    The Passenger Pigeon population growth and hunting practices

    • Modern example of overkill

    • At the beginning of the 19th century, flocks stretched across North American skies for up to 500 kilometers.

      • In less than a century, this seemingly ineradicable species was utterly extirpated.


    Na ve species meet invasive omnivore species
    Naïve species meet population growth and hunting practices invasive omnivore species

    • Historical and modern extinctions in isolated / island ecosystems

      (Boyer 2008; Martin 2005)


    Overkill alone is likewise insufficient
    Overkill alone is likewise insufficient. . . population growth and hunting practices

    Extinctions prior to invasion of Homosapiens

    Long duration of coexistence

    • Loss of naïveté

    Europe and Northern Asia

    (Hofreiter and Stewart 2009:R589)


    Hyperdisease
    Hyperdisease population growth and hunting practices

    • 113 North American mastodon skeletons / various geographic regions

      • 52% exhibited signs of tuberculosis

        (Rothschild and Laub 2006)

    • Infection evident 34,000 – 10,000 years BP

    • Populations greatly weakened

      • More susceptible to climate change / overkill

    (Rothschild and Laub 2006:562)


    Historical validation
    Historical validation population growth and hunting practices

    • 1st recorded extinction by infection in a free-ranging wildlife species

      • Sharp-snouted day frog

  • 1 other historical case of extinction by infection (in a remnant captive population)

    • Polynesian tree snail

      • (Schloegel et al. 2006)


  • European introduction of diseases such as measles and smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).


    Hyperdisease alone insufficient
    Hyperdisease alone insufficient. . . smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).

    • 20 glacial-interglacial periods / 2 million years

    • Many opportunities for novel pathogen introduction

      • Mass extinctions only occur near the end of the Pleistocene and only in large land animals

        • No known analogous pathogens (such as West Nile virus) demonstrate such size selectivity

          (Lyons et al. 2004b)


    A multicausal approach
    A multicausal approach smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).

    Climate Change + Infection + Keystone Invasive Species = Mass Extinction Event

    with Homosapiens tipping the scale. . .


    Homo sapiens
    Homo sapiens smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).

    . . . an invasive species

    with life-negating metaphysical beliefs

    about. . .


    The inexhaustibility of natural resources
    The inexhaustibility of natural resources smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).


    Homo sapiens as quasi divine
    Homo sapiens smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).as quasi-divine

    fundamentally separable from all other life forms that have ever existed on the Earth


    • Entitled to: smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).

    Exterminate

    Occupy

    Invade

    Exploit

    Commoditize

    Consume

    with little regard for the consequences


    Behold the rational animal
    Behold the Rational Animal. . . . smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).

    Man has been educated by his errors: first, he saw himself only incompletely; secondly, he endowed himself with fictitious attributes; thirdly, he placed himself in a false rank order in relation to animals and nature; fourthly, he invented ever new tables of goods and for a time took them to be eternal and unconditioned . . . .

    Nietzsche, GS 115 (1882)


    Current extinctions
    Current Extinctions smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).

    One species every 20 minutes.

    This rate is more than one thousandfold greater than the natural background rate (Pimm et al. 1995, Wilson 1992).

    (Gorke 2003:1)


    Even smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).though human-induced species extinction presently seems to rank low on people’s attention scale compared to other political and societal topics, this does not mean that its significance in earth history or its ecological consequences have diminished in any way. It must repeatedly be made clear that if current trends continue, within the next one hundred years half of all our planet’s species will most likely have become extinct. Thus, members of today’s generation are witnesses and also perpetrators of the greatest catastrophe in the history of life since the disappearance of the dinosaurs 65 million years ago.

    - Martin Gorke, 2003


    http://www.digitalsurvivors.com/archives/worldpopulation.php smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).


    Nonhuman megafauna s loss of habitat and access to migratory routes
    Nonhuman megafauna’s loss of habitat and access to migratory routes

    due to Homosapiens’ expanding invasion of ‘novel’ ecosystems




    The fragmentation of natural habitats essentially creates isolated ‘islands’ where species’ vulnerability to extinction is heightened as the ecosystem processes and services they depend on for survival are disrupted by biodiversity reduction, competition with invasive species over a shrinking resource base, pathogen dispersal, pollution, and numerous other anthropogenic factors.


    The megafauna du jour
    The megafauna du jour isolated ‘islands’ where species’ vulnerability to extinction is heightened as the ecosystem processes and services they depend on for survival are disrupted by biodiversity reduction, competition with invasive species over a shrinking resource base, pathogen dispersal, pollution, and numerous other anthropogenic factors.


    Consumption patterns of industrialized nations are not ideals for which the ‘developing’ world should strive.

    • based on short-term ‘profit’ and convenience for a ‘wealthy’ minority

    • ignore effects on biodiversity and the long-term survivability of megafaunal species such as our own


    Over consumption of toxic and limited resources
    Over-consumption of toxic and limited resources ideals for which the ‘developing’ world should strive.


    If India alone adopted the consumption pattern typical in the US, the global ecological impact would be as if the world’s population had doubled to 13.2 billion (Cox 2008:114).


    The inexhaustibility of natural resources1
    The inexhaustibility of natural resources. . . the US, the global ecological impact would be as if the world’s population had doubled to 13.2 billion (Cox 2008:114).


    A false and ultimately life negating premise
    . . . a false (and ultimately the US, the global ecological impact would be as if the world’s population had doubled to 13.2 billion (Cox 2008:114).life-negating) premise.

    Hubris today characterizes our whole attitude towards nature, our rape of nature with the help of machines and the completely unscrupulous inventiveness of technicians and engineers.

    - Friedrich Nietzsche, GM (1887)


    Ecosystems eventually bounce back
    Ecosystems eventually ‘bounce back’. . . the US, the global ecological impact would be as if the world’s population had doubled to 13.2 billion (Cox 2008:114).


    . . . but not always on an anthropocentric timescale. the US, the global ecological impact would be as if the world’s population had doubled to 13.2 billion (Cox 2008:114).


    It usually takes 10 million years for Earth’s multicellular biodiversity to ‘return’ to pre-mass-extinction levels. It took 100 million years after the end-Permian event (Benton 2003:155).


    The duration of multicellular biodiversity to ‘return’ to pre-mass-extinction levels. It took 100 million years after the end-Permian event (Benton 2003:155).Homo sapiens’ tenure depends on future consumption practices.


    Homo multicellular biodiversity to ‘return’ to pre-mass-extinction levels. It took 100 million years after the end-Permian event (Benton 2003:155).sapiens is part of the natural world and is just as susceptible to extinction as Earth’s other organic beings.


    The x factor
    The X Factor multicellular biodiversity to ‘return’ to pre-mass-extinction levels. It took 100 million years after the end-Permian event (Benton 2003:155).

    Earth is becoming less biodiverse as a result of the escalating global invasion and consumption practices of Homosapiens.

    What kind of biosphere are we creating? Will it support the continued existence of organisms such as ourselves?




    The post human earth
    The Post-Human Earth extinction.

    It’s a small world, after all. . . .


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