Yes, species extinction has always occurred (as noted in Forbes, “Species extinction is nothing new” (June 15, 2012), but the author’s implication that it has nothing to do with CO2 is entirely false.
Counter to claims in the letter, factors associated with increase of CO2, ie, global warming, acidification of oceans and lack of oxygen have featured in most if not all of the earth’s five mass extinctions (http://www.stateoftheocean.org/ipso-2011-workshop-summary.cfm).
The rate of increase of CO2 has been estimated at 1 – 2 gigatons (Gt) of CO2 per year for the End Permian Extinction (251 million years ago) and 2.2 Gt/yr for the Paleocene Eocene Thermal Maximum Extinction (55 million years ago). At roughly 30 Gt CO2/yr, today’s emissions are nearly fourteen times higher than these levels.
These estimates raise the possibility that rate of the mass extinction almost certainly now underway may be much higher than in the previous events.
A timely example for Australians lies in our own seas, which are warming and acidifying. Their ecosystems are threatened in addition by overfishing, pollution and loss of habitat. Our new Commonwealth Marine Reserve system may give them a second chance.
Humans are unique on earth in our ability to think, analyse, evaluate and act. Let’s not use the head in the sand approach advocated by the Forbes letter. Let’s each do our best toward reduction of CO2 emissions, and urge governments to do the same. With business as usual, we ourselves may become one more extinct species.
Joan Vickers
Harlaxton
