Rog I gotta disagree; I don't think Silversides was way off topic, or even off topic... I don't agree, but I do think we are discussing the salient point here...
Invasives are invasives for one reason alone really, human introduction. Left to their own devices, plants can move in response to shifting climate or ecological opportunity, but in this case the ecosystem they are moving to has time to adapt itself to the introduction. It has been the rapidity of the human vector that has allowed so many plants, animals insects and diseases to spring fully formed into am ecosystem with disruptive result.
Our human history is littered with ecosystems and civililzations despoiled by our transport of biology to places not yet ready. How did 200 Spaniards defeat the Incan Empire? From a germ the Spanish carried (given to them not incidentally by the cows they raised; food is a serious consideration in the invasive conversation).
Look at any invasive issue of serious concern in the U.S. and you quickly see that we gardeners are responsible for the big majority of these issues. Our "adjustment of our surroundings" has deprived us of some of the most productive forest trees in our country (chesnut, elm) and threatens countless others (hemlock, oak, ash, dogwood etc.). Our assumptions of safety and resiliant ecosystem have been wrong time and again, and good work by folks like Doug Tallamy show that more often than not, even the most seemingly innocuous addition deprives a natural community of some valuable link.
I am reminded of the Aldo Leopold quote...
The outstanding scientific discovery of the twentieth century is not television, or radio, but rather the complexity of the land organism. Only those who know the most about it can appreciate how little we know about it. The last word in ignorance is the man who says of an animal or plant: "What good is it?" If the land mechanism as a whole is good, then every part is good, whether we understand it or not. If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering.
Too often we have done just this with the use of an invasive to suit our own ends. The use of broom seems suited to our needs, but it disposes of many natural plants with an indiscriminate dispersion of genetic material and seed with no thought. Mustard is another permie darling plant that has no place on this continent, but I fear we are saddled with it to the detriment of the environments it now pollutes (the correct term in my mind).
One cannot be pro-environment and pro-invasive; the realities of the biota preclude one from the other. TRUE permaculture should embrace the environment it coexists in by valuing native inclusion above all others, and non-invasive plant materials as suitable adjuncts. The use of invasives is more damning than the use of tilling, or oil, or many of the other tools permies love to hate. I do not get the disconnect here; it is integral to ecological thinking...
HG
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