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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).

slide8

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)

slide11

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. . .
  • 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)

a smoking spear
A Smoking Spear?
  • 76 North American Clovis sites reviewed
    • 14 contained extinct megafaunal remains
        • 12 – mammoths
        • 2 – mastodons

(Grayson and Meltzer 2002)

slide15
Mass extinction inevitable – even with moderate human population growth and hunting practices(Alroy 2001:1895)
buffalo jumps
Buffalo Jumps
  • 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
  • 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 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. . .

Extinctions prior to invasion of Homosapiens

Long duration of coexistence

  • Loss of naïveté

Europe and Northern Asia

(Hofreiter and Stewart 2009:R589)

hyperdisease
Hyperdisease
  • 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
  • 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)
slide22

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. . .
  • 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

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

with Homosapiens tipping the scale. . .

homo sapiens
Homo sapiens

. . . an invasive species

with life-negating metaphysical beliefs

about. . .

homo sapiens as quasi divine
Homo sapiens as quasi-divine

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

slide28

Entitled to:

Exterminate

Occupy

Invade

Exploit

Commoditize

Consume

with little regard for the consequences

behold the rational animal
Behold the Rational Animal. . . .

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

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)

slide31

Even 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

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

slide36

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.

slide38
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
slide40

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).

a false and ultimately life negating premise
. . . a false (and ultimately 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)

slide45

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).

slide47

Homosapiens 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

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

It’s a small world, after all. . . .

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