The Sixth Extinction

The Sixth Extinction: An Unnatural HistoryI have been aware of the large number of extinctions that we’re causing.  What I haven’t been aware of is the idea of ecosystem extinction.  “It is likely that [coral] reefs will become the first major ecosystem in the modern era to become ecologically extinct.”  Very frightening because “it is estimated that at least half a million and possibly as many as nine million species spend at least part of their lives on coral reefs.”

There have been five mass extinctions, The Big Five, in the earth’s history plus a number of lesser extinctions.  We are in the midst of the sixth biggie.

Amphibians enjoy the dubious distinction of being the world’s most endangered class of animals; it’s been calculated that the group’s extinction rate could be as much as forty-five thousand times higher than the background [extinction] rate.  . . . one third of all reef building corals, a third of all freshwater mollusks, a third of sharks and rays, a quarter of all mammals, a fifth of all reptiles, and a sixth of all birds are headed toward oblivion.

We are driving this latest mass extinction by these geological-scale changes:

  • Human activity has transformed between a third and a half of the planet’s surface.

  • Most of the world’s major rivers have been damned or diverted.

  • Fertilizer plants produce more nitrogen than is fixed naturally by all terrestrial ecosystems.

  • Fisheries remove more than a third of the primary production of the ocean’s coastal waters.

  • Humans use more than half the world’s readily accessible fresh-water runoff.

  • People have altered the composition of the atmosphere [and the oceans].  Owing to a combination of fossil-fuel combustion and deforestation, the concentration of carbon dioxide in the air has risen by forty percent over the last two centuries, while the concentration of methane, an even more potent greenhouse gas, has more than doubled.

What, in the midst of this sixth, mass extinction, is going to happen to us, to homo sapiens?

One possibility is that we too will eventually be undone by our “transformation of the ecological landscape.”  The logic behind this way of thinking runs as follows:  having freed ourselves from the constraints of evolution, humans nevertheless remain dependent on the earth’s biological and geochemical systems.  By disrupting these systems – cutting down tropical rainforests, altering the composition of the atmosphere, acidifying the oceans – we’re putting our own survival in danger.  Among the many lessons that emerge from the geological record, perhaps the most sobering is that in life, as in mutual funds, past performance is no guarantee of future results.  When a mass extinction event occurs, it takes out the weak and also lays low the strong.

Another possibility – considered by some to be more upbeat – is that human ingenuity will outrun any disaster human ingenuity sets in motion.  [No logic presented for this possibility.]

I have little hope than mankind can think or invent our way out of the dilemma we have gotten ourselves into.  I fear that those who believe that human ingenuity will ride to our rescue are the same one who will not take the threat seriously.

What, me worry?  The scientists will think of something.






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