In an article posted on CBS News, Michael Casey writes that some scientists think we are entering the 'sixth extinction'. He makes the argument that 676 species have gone extinct in the past 500 years. Further, he states that under 'normal' circumstances - normal meaning without humans - that rate of extinction should have taken place over 11,000 years.
It sounds horrible and in fact, when a species becomes extinct, it is indeed a tragedy.
However, he is way off the mark in his conclusions.
Let's look at the total number of species on the planet today. Estimates run between 2 million and 50 million extant species alive and kicking. Granted, not all of these species are doing well - some are close to extinction. However, when you divide 676 by the lowest estimate of two million, you get 0.000338, or 0.03% of total species.
That means 99.97% of all species still exist in the world today. Is he claiming that 0.03% equals a mass extinction? Previous extinctions eliminated the following percentage of species:
1) Cretaceous–Paleogene extinction event : 75%
2) Triassic–Jurassic extinction event : 70 - 75%
3) Permian–Triassic extinction event : 90 - 96%
4) Late Devonian extinction : 70%
5) Ordovician–Silurian extinction events : 60 - 70%
I can hardly agree with the author that what we're seeing is a 'sixth mass extinction' on the level of these listed major events. To be fair, however, the author states that we are entering the sixth extinction. That remains to be seen, of course. It's easy to make these claims when you have to wait half a century for the claim to be verified. Even at the current rate of extinction, in '40 or 50 years' (as the article states), you are looking at less than one hundred new extinctions.
When it comes to humans being unnatural, I find this remark unrealistic at best, and fueled with self-hate at worst. Human are natural. We evolved here just like every other species and we are as natural to planet Earth as any other species that has ever existed or ever will. The Earth produced us.
That doesn't mean that we aren't linked to species extinction - we are. We are also linked to species preservation. Will our efforts be enough to halt the rate of extinction? I'm all for species preservation and maximum biodiversity, as is, I'm sure, the author. Only time will tell, but I for one would appreciate a more balanced article when reporting on same.