I might have not expressed myself well in the previous comment, but when I say that "New species are also continuously emerging", it is to prove that the background extinction rate is not zero, not that we don't have a problem.
The curve that he fitted is not the net extinction rate. It's simply the total number of extinctions.
The graph he plots shows the total number of extinctions at year 1000 being 0 or almost 0. This is an assumption. In the absence of humans the extinction rate could be 1,2,10 per year, whatever, it's some small number. The point is that when you are fitting an exponential curve to 3 data points, the resulting curve will be very sensitive to small changes in the value of that point at year 1000. In particular, choosing a value of 0 will force the model towards the steepest possible gradient that the model can allow. i.e. it's biased towards alarmism.
EDIT: Although, when I think about it a little more, a reasonable model would model the extinction rate as an exponential plus a constant value, which would change things. Though a reasonable model probably wouldn't assume an exponential model at all based on 2 data points
The curve that he fitted is not the net extinction rate. It's simply the total number of extinctions.
The graph he plots shows the total number of extinctions at year 1000 being 0 or almost 0. This is an assumption. In the absence of humans the extinction rate could be 1,2,10 per year, whatever, it's some small number. The point is that when you are fitting an exponential curve to 3 data points, the resulting curve will be very sensitive to small changes in the value of that point at year 1000. In particular, choosing a value of 0 will force the model towards the steepest possible gradient that the model can allow. i.e. it's biased towards alarmism.
EDIT: Although, when I think about it a little more, a reasonable model would model the extinction rate as an exponential plus a constant value, which would change things. Though a reasonable model probably wouldn't assume an exponential model at all based on 2 data points