I heard recently that some 260 million years ago a series of events occurred on earth which resulted in the death of 97% of all living things on earth. (I do not know if that 97% meant of all individual living things, or represents the percentage of species which went extinct. I would like one of you who is in the know, to clarify this point.) This massive die-off has been called The Great Dying.
I have also heard that the cause was volcanoes in the area of Siberia filling the air with aerosols. The primary killing aerosol was hydrogen sulfide. Again, I would like one of you who knows the facts to clarify or correct this point.
Now to my questions.
- How does the earth, currently, stand in comparison to the climactic conditions which caused The Great Dying?
- If the conditions (i.e. type of killing aerosol(s)) are the same, how close to the same concentrations is the earth at this time.
- If the conditions are the same, is there a cascade-point at which climactic feedback loops can be reasonably expected to cause the earth to reach a similar Great Dying?
Conditions today aren't quite the same. Without the huge volcanic eruptions, the aerosols are far lower. At the End Permian times, the supercontinent of Pangaea occupied most of one hemisphere from poles to equator, while the huge Panthalassa ocean covered the other. Atmospheric and oceanic circulation and temperature distribution systems were very different than today. Over the long term, the climate seems to have been very unstable, producing a number of mass extinctions during the period leading up to the Great Dying.
One of the most notable aspects of this greatest of extinctions, IMO, is just how long the poor environmental conditions lasted. Not only did the extinction itself display a complex series of patterns, seemingly affecting different groups at different times, but the recovery took a very long time, because the Earth apparently remained largely uninhabitable for possibly millions of years.
What's happening today is far more rapid, more comparable to an asteroid impact than a drawn out volcanic disaster. The initial conditions are also different -- the Permian world was warmer to start with, we are warming from within an ice age. An isolated southern continent today, Antarctica, and a restricted Arctic basin allow the accumulation of ice caps, which means lower sea levels than existed during End Permian times.
There are similarities, but there are also differences, these differences include the arrangement of landmasses and ocean basins, circulation systems, the types of plant and animal species and their interactions, starting temperatures and CO2 concentrations, the types of pollutants being emitted, the sources of pollutants being distributed rather than concentrated in a single region, global habitat destruction occurring independently of CO2 release, and the great rapidity with which today's changes are happening. In short, it's not going to be easy to use one event to analyze the other.
I don't anticipate a drawn-out 4 million year long tail to this particular mass extinction, but that will be small comfort to the many species that disappear, and the many individuals who suffer for no good reason.