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Extinction lesson from past
I READ Kate Lock’s article on the possible demise of the polar bears with interest. (The Press September 21.) Kate also writes “Scientists....are using words like planetary catastrophe...uncharted territory.”
However, Earth may have been here before and well before humans.
The first dinosaurs evolved in the Triassic, some 250 million years, ago. However, during the Permian era, 252 million years ago, a mass extinction occurred, both on land and at sea. Life on Earth took ten million years to recover.
A theory is the positive feedbacks, like methane release that Kate mentions, led to polar ice melt and in turn led to failure of the ocean circulation known as the global conveyor.
That led to extinction of life in the oceans which became more like a stagnant pond on a large scale as the mixing currents failed, and extinction on land, as hydrogen sulphide gas from the stagnant “pond” changed the composition of the atmosphere and made land life struggle to survive.
A message from the past?
Chris Clayton, Hempland Drive, York
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