Saturday, June 9, 2012

Extinction



The coral reefs are dying. These largest of all earth’s living structures, intricate and brightly colored, home to a vast panoply of colorful fish, mollusks, marine life of all kinds -- the superstructure of biologically diverse ecosystems -- are bleaching white, breaking up, and withering away.
It won’t be the first time that the reefs have died away. In each of the five previous mass extinctions, coral reefs have been severely impacted, taking many millions of years to recover. In this respect, reefs are like the canary in the coal mine. They are a sentinel, whose current calamitous condition foretells the sixth mass extinction, an event many paleontologists believe the earth has already entered.
The cause or causes of earth’s previous mass extinctions have been a matter of intense scrutiny. Hypotheses have ranged from massive volcanism to asteroid strikes. 
The Permian-Triassic extinction of 250 million years ago (Mya), wiped out over 90% of the planet’s marine species. On land, over 70% of reptile, amphibian, insect, and plant species went extinct. It was the most catastrophic of all earth’s extinctions, and may have been triggered by the eruption of the super volcano known as the Siberian Traps, the most massive eruption and lava flow in earth’s history.

The Siberian Traps eruption, which lasted for a million years, added huge amounts of heat, carbon dioxide, and sulfur dioxide to Earth's surface and atmosphere, and the resulting greenhouse effect generated a long warming trend. The climate change triggered by the warming dramatically shifted weather patterns across the globe.
Carbon dioxide has left its fingerprints on all the massive die-offs experienced during earth’s often violent history. J.E.N. Vernon (2008) has pointed out in his article in the journal Coral Reefs, that recent palaeophysiological studies have clearly implicated CO2 in the destruction of most life on earth during the Permian-Triassic extinction.
There is also evidence of a sudden and massive release of methane, perhaps triggered by increased warming. This would have been an example of positive feedback, that is, CO2 causing warming, melting frozen tundra, and thereby releasing methane, which is considered a much more potent greenhouse gas than CO2.
As it happens, Russia’s Siberian tundra is currently melting. Russia has the largest extent of permafrost in the world. Scientists estimate that permafrost covers more than 10 million square kilometers of Russia. The warming planet is melting permafrost in Siberia, and the melting permafrost is releasing methane in much greater quantities than previously thought. Methane is considered 20 times more damaging as a greenhouse gas than carbon dioxide, which means that Siberia is now actively contributing to  warming. Russian scientists believe the melting of Siberian permafrost is irreversible, as the release of green house gases will perpetuate the warming climate.

Experts say Siberian tundra leaking methane in record amounts
And this brings us to the Sixth Mass Extinction -- the one happening now. We’ll address that in a coming blog post.

No comments: