Thursday, June 2, 2005

Major species extinction periods

There's a few articles in the news right now talking about species extinction. There's been five previous periods where a major amount of species went extinct all at once. All of those were due to external forces (climate change, and meteor impact).

Today it seems that we are in the middle of a major extinctionary period, and the difference today is that we are the cause. We humans are causing major stress to the environment of this planet, and it is that stress which is causing species to die off.

The Sixth Extinction (By Niles Eldredge,, June 2001)

At first glance, the physically caused extinction events of the past might seem to have little or nothing to tell us about the current Sixth Extinction, which is a patently human-caused event. For there is little doubt that humans are the direct cause of ecosystem stress and species destruction in the modern world through such activities as:

  • transformation of the landscape
  • overexploitation of species
  • pollution
  • the introduction of alien species

And because Homo sapiens is clearly a species of animal (however behaviorally and ecologically peculiar an animal), the Sixth Extinction would seem to be the first recorded global extinction event that has a biotic, rather than a physical, cause.

... We can divide the Sixth Extinction into two discrete phases:

  • Phase One began when the first modern humans began to disperse to different parts of the world about 100,000 years ago.
  • Phase Two began about 10,000 years ago when humans turned to agriculture.

I think he's missing the third phase. Namely, 150 years ago when Oil began to be exploited, it was Oil that allowed for the great amplification of humanities effects on the planet. Perhaps you could push the date back a little, to the first coal and steam powered engines such as was used in railways.

In any case, the use of fossil fuels is what gave us humans the energy with which to reshape the planet. Prior to fossil fuels, our agriculture was largely dragging sticks along the ground, and had to be highly organic in nature. After fossil fuels we had machines available to dig up whole mountains to, for example, get the copper buried underneath.

He does go on to say this:

Homo sapiens became the first species to stop living inside local ecosystems. All other species, including our ancestral hominid ancestors, all pre-agricultural humans, and remnant hunter-gatherer societies still extant exist as semi-isolated populations playing specific roles (i.e., have "niches") in local ecosystems. This is not so with post-agricultural revolution humans, who in effect have stepped outside local ecosystems. Indeed, to develop agriculture is essentially to declare war on ecosystems - converting land to produce one or two food crops, with all other native plant species all now classified as unwanted "weeds" -- and all but a few domesticated species of animals now considered as pests.

And, obviously, there is truth to this. No matter how primitive that agriculture was, it did change the landscape and habitat. And he also mentions how in every place humans traveled to, they killed off whatever large beasts were in that area. e.g. the Sabre-Tooth Tigers of North America that disappeared shortly after humans first arrived there.

Extinction on the Horizon for One-Fifth of All Bird Species (CAMBRIDGE, UK, June 1, 2005, Environmental News Service)

Logging ban urged to protect caribou (Canadian Press, May 31, 2005)

Royal Bengal tiger faces extinction threat (Kolkata, May 25, The Hindu)

UNDP Warns On Extinction of 15,000 Animal, Plant Species (Angola Press Agency (Luanda), May 22, 2005, Posted to the web May 23, 2005 )

UN Millennium Ecosystem Assessment Report warns worsening ecosystem changes put Millennium Development Goals at risk (60 percent of earth’s ecosystem services being degraded or used unsustainably; the poor most affected; United Nations, 4 April 2005) See: Synthesis reports

Report Shows Extinction Crisis for Animals