Dozens of studies have looked at the effects of Japanese knotweed on natural communities in Europe and North America. (blog.pensoft.net)
Also, the machinery used can carry pieces of knotweed to new locations. (remonline.com)
If we're ready to somehow equate humanity with knotweed, and admire (or regret) both for their ability to occupy niches, well how about AIDS? (dotearth.blogs.nytimes.com)