The disappearance of such a dominant tree species from the Appalachians might have been expected to have had far more major consequences for the survival of other species in the ecosystem than it apparently has had. If the fungus had arrived before European settlers, it is unlikely that the absence of chestnuts would even have been noted. On the other hand, James Kirkley, a biologist at the Virginia Institute for Marine Sciences, once told me that he would be happy to seed the Chesapeake Bay with Asian oysters. Because overfishing and two fierce diseases have decimated native oysters so that oyster populations are less than 1 percent of their original levels. As a result, Chesapeake Bay waters have become much murkier.
Asian oysters are very similar to native ones but resist disease more successfully.
Which is exactly what we would want them to do. In this case a non-native species would be filling an ecological niche that has been opened by disease. Good reasons exist for taking pride in local flora and fauna. That doesn't mean it isn't valid, but it does mean that ecologists and environmentalists can't simply justify their preference for native species on the basis of economic fiddling that willy-nilly lumps together basically benign alien species along with bad actors. Ecology should not attempt to become a normative science.