Acknowledging how difficult it would be to map every invasive plant in the world by hand, researchers at U.C. Davis are out to do it all by plane. According to this story at discoverynews.com, the scientists flew a plane over areas of California coast invaded by ice plants (Mesembryanthemum crystallinum) and jubata grass (Cortaderia jubata), and used remote sensing to record digital images of the landscape. The ice plants gave off a distinct signature that could be easily pinpointed over the region studied, while the jubata grass was a bit harder to identify. You can read the full details of the study in this article published in the journal Remote Sensing of Environment (or if you don't subscribe, you can just read the abstract :-).