Are they something not just to be tolerated buy accepted?
Have our assumptions about ecological stasis led us to some bad assumptions?
I think we have some strange ideas about ecosystems. Ecosystems are constantly changing. There really isn't a native ecosystem anywhere, and certainly if there were any, they've been messed up by humans for a long time.
They are constantly evolving, constantly changing; species are moving in and out. So the whole idea of a pristine, stable, unchanging, natural ecosystem is just getting nature wrong. And an increasing number of ecologists take this line as well.
If we think about species in Australia, for instance, is the dingo a native or an alien? It feels quite native these days, but actually it was brought in from South East Asia a few thousand years ago. It was an early example of humans moving species around the world.
Ecologists often talk about the 21st century as the century in which we encourage nature to recover. ‘Ecological recovery’, ‘ecological restoration’: these are phrases that ecologists talk about a lot. And I'm very much in favour of that, but I don't think we are going to do that just by native species. I think we need the colonists, the species that can do well in damaged environments. And alien species have a real track record of doing that; that's why they survive.
In praise of invasive species