This one is because of folks. Particularly during this Century, this decade, we are destroying native environments at an unbelievable pace. Because we, ourselves, are doing the deed, politics is in the way of our being objective about just what we are doing. Environmentalists on the one side, loggers on the other, and the folks voted vertebrates down, even though they did not understand they they were doing that. What is happening matters to us, and this makes it hard to objectively view what is happening.
Dams contribute in a major way towards wiping out populations of fish.
We know this now, we didn't only a few years ago. Douglas Green, the UO graduate quoted at the top of this write-up, might even have believed what he wrote. Figures of the size of the kill are astounding. Many big vertebrates, mammoths, saber-toothed tigers, dodos, that were around in the Pleistocene are gone now. In spite of the obvious glamour associated with condors and hippos, and in spite of a desire on our parts to keep big animals like whales around, the big ones are the most vulnerable.