I'm not sure what point you're trying to make, BC. A plague of rabbits is ecosystem destruction and kills a bunch of other species.
Exactly. And events such as plagues of rabbits happened all the time in nature, before human beings ever existed. And not always for the better, either. Without humans in the equation, ecosystem destruction is simply part of the system.
According to the laws of Nature (which are really mean and cruel) bad genetic code needs to be eliminated in order to prevent things such as birth defects from polluting a species. When a species has lots of bad genetic code in it, what happens? Its ability to survive is impaired, and the species (usually, but not always) goes extinct. But Nature is pretty haphazard about this; a number of species are able to deal with whatever handicaps their genes inflict on them.
The problem lies in figuring out which extinctions are actually bad, and which are beneficial. Human beings are an exercise in failure on that score; when a child is born with sickle cell, or hemophilia, or cystic fibrosis, or whatever other genetic disorder, what do we do? We try to save the poor kid--and thanks to our advanced medical technology, we generally succeed. Result: genetic disorders propagate in humans at accelerating rates. This doesn't happen in nature, because most infants born with such disorders die before they get a chance to reproduce.
So we come down to the question--which extinctions of endangered species are actually bad?? When we preserve endangered species, are we doing a good thing, or allowing poor genetic code to propagate in a system? (we do the latter all the time with our own pets.....)