The gypsy moth problem where I'm from seems like it could become genuinely catastrophic in a few years. That or we figure out how to seed clouds with BTK /s
Recently moved from a town with an infestation. Returned a week later, and no exaggeration, 90% of the leaves in my neighborhood had been chewed away. Even ones where residents had taken steps to protect the tree. I'm not old but I haven't seen devastation like that from an invasive species here in Ontario before.
I saved my beech tree by wrapping the trunk in burlap starting mid-may, and then burning it/squishing all the (thousands of) caterpillars under it on a weekly basis. It has been traumatizing, but my tree is fine. I also sprayed BTK on my small fruit trees and they have been unaffected. So it can be done... but it is time consuming and disgusting.
Humans being the invasive species?
You could argue that, but mainly the species that get introduced directly and indirectly by human activities.
I was thinking plant species: kudzu, Scotch broom, etc.