Planting Trees

Last Wednesday, as well as the following Wednesday, the class will be planting the native trees Western Soapberry (Sapindus drumondii) and Netfleaf Hackberry (Celtis reticulata). These are two trees that I am not familiar with as far as planting goes but every summer I spend most of my time landscaping for a friend's business. Most of what I'm familiar with are desertscapes, which is interesting, because this type of landscaping is targetted at the removal of plants unable to deal with the hot summers and cold winters of Lubbock, or non-native species of plants, and replacing with drought/cold-tolerant perennials! Here is an excellent landscape website that includes many very pretty, native or drought-resistant plants to look through!
http://bexar-tx.tamu.edu/HomeHort/F4Best/nTxLSPerennials.htm

There is a nursery in south Lubbock that specializes in native or drought-resistant plants (the name currently eludes me, not Sparkman's - it isn't even listed on Google maps!). All in all it was a great day! I don't think there is anything more enjoyable than working outdoors when the weather is as pretty as it was on Wednesday! Anyways, after class I went to Rosa's to pick the brain of Burr Williams after class... I had a question that has been nagging me since we first started talking about invasive species. My question was, "If evolution has "fashioned" a species better adapted to an area that it invades, am I wrong for thinking that there is a degree of hypocrisy associated with the efforts of fighting off said species?" This was presented after stating to Burr Williams that I realized some, if not most, of these plants were introduced to ecosystems in what people consider an "unnatural" way in that humans had transported them to the new ecosystem.

His response was amazingly unpredicted, "No." And then a laugh. And from here on out I'm summarizing. -It seems that we as people tend to forget that humans are as much a "disruptive species" as the invasives trying to be removed in the previous question. We are a part of the ecosystem, not excluded from it, and as such play the same roles as every other species on the planet. So I thought I'd ask anyone who reads this what your perspective is.

If an invasive species demonstrates a higher level of fitness than the native species present (species that have adapted for literally the exact ecosystem they are currently living in, sans the newly introduced invasives or tampering from humans; e.g. deforestation, nitrate removal, etc.), should humans allow nature to take the course it would ... naturally?

Trust me; I understand the point about responsibility for environmental changes attributable to human activity, human disruption within ecosystems, etc. I just want to know how you feel about the aforementioned question analogous to Bengal tigers eating or being eaten by, say, polar bears should one ever enter into the environment of the other, by whatever means.