Someone forwarded me a thoughtful article from the Science section of the New York Times, entitled “Friendly Invaders.”
Drawing on the work of Dr. Dov Sax (Brown University) and Dr Steven Gaines (UCSB), and also Dr James Brown of the University of New Mexico (among others), it points out that ïnvasive species” very seldom drive native species to extinction. Instead, they increase the biodiversity of the area to which they’re introduced.
Peopl often think of an ecosystem as having a limited number of niches, which Drs Sax and Gaines argues is not true. Exotics can create additional niches. Local species adapt to those niches, often through a process of rapid evolution. (Evolution can go really fast for species that reproduce rapidly and have large numbers of offspring.)
I thought this was particularly interesting in the context of eucalyptus forests. There’s evidence that something like 100 native species of birds and animals use eucalyptus forests and habitat. They’ve adapted to eat the seeds, eat the insects found under the peeling bark, nest in trees (including, apparently, under the peeling bark), and hide in the thick duff that forms under these trees.
A quote from the article: “I hate the ‘exotics are evil’ bit, because it’s so unscientific,” Dr. Sax said.
Mount Sutro Forest That Was 
I hope you guys (and the global warming denialists) are right because once this happens we can’t go back!
Actually, we recognize climate change is occurring. That makes native plant restoration even more complex; the climate in the restored area may be changing from its historical patterns, and that may be a further factor in changing vegetation patterns.
It’s already too late to turn back. We’re not going to live on local acorn flour and fish and game, we live in a globalized world. Like the Great American Interchange, this is causing a major movement of species, whether by accident or design (i.e., human accident or design).