During the 1980s there was increasing recognition that the rate of species loss really is not known. One would think that this absence of knowledge would make anyone leery about estimating future extinctions. This is mere speculation, however. And as noted above, Lugo found disconfirming evidence in Puerto Rico. Yet the conservationists go right on pressing for expensive public policies on the unproven assumption that the number of species being extinguished is huge.
Many biologists privately agree that the extinction numbers are quite uncertain.
But they go on to say the numbers do not matter scientifically. The policy implications would be the same, they say, even if the numbers were different even by several orders of magnitude. I find no scientific justification for such use of numbers. Obviously we do not know the answers. But it seems hard to even imagine that we would be enormously better off with the persistence of any such imagined species.