I'd like to jump in on that. I think the important thing here—I'm sure you can ask my friend the professor here about his technical terminology—is triage. You're looking at what will have the largest impact on your environment. In the west it might be cheatgrass, which increases the risk of fires on rangeland. It might be Scotch broom, which also chokes out a lot of other plants and increases the risk of fires. It might be invasive mussels that have a huge ecosystem impact.
Certain species are like the dirty dozen, or the dirty 50, or something like that, that are just known, when they come in, to have a huge impact. In the yard next to my house, there is a tree that is an invasive species in Arizona. I just moved into that house. I laughed, because I know that millions of dollars are spent eradicating it in Arizona, but it is not invasive in Kelowna. You really have to use your intelligence, use the tools you have and do the risk assessments. Some are bad and some aren't.