Thank you. (Ambrosia artemisiifolia is a carantine plant species, I used it as an example because it's notorious for having allergenic pollen, contributing to desertification - its roots can reach about 4m down, maybe more - and is rather easy to recognize, but people just don't care to eradicate it or at least cut off the inflorescences. And yes, in many places its spread is already unstoppable. Some other plants of the same genus are carantine weeds, too.)

I referred rather more to pathogens that could arise and benefit from totally manmade environments. (I remember from somewhere that in supermarkets all over the world, the same six species of Drosophila occur; I think that transportation and storage networks can be modeled as ecosystems, especially if more and more stuff gets produced.)