I live in West Virginia. Autumn olives are a nightmare of invasiveness here, worse than multiflora because if you dig out the crown of a multiflora, you've killed it but with autumn/Russian olives you have to dig out every bit of
root. To the person who said he sees a single autumn olive that hasn't notably spread, I say GET RID OF IT WHILE YOU CAN! To those questioning whether goumi is a better option, I believed a book that said they were and got two--a Sweet Scarlet and Red Gem. This was 4 or 5 years ago. I've seen no sign of their spreading. They require zero care--I do prune them in February, to make picking in late June easier, not a lot of trouble and as some say, you can use the prunings. This year I'm going to use many of them as starter for cuttings to try to make lots more, to give away and I think I'll add a couple more in my orchard. They fix nitrogen, They have pretty silvery leaves and pleasant smelling flowers (so do the evil autumn olives). Every year I get lots of fruit--picking the berries in the main chore, it takes several hours over a couple of days. The negative is that the berries have sizable pits, and the only way I've found to deal with them is to steam the fruit for 20 minutes or so and filter out the solids, then use the liquid for a syrup. They are loaded with antioxidant and other good things.
I think invasives generally do tend to settle into an ecosystem eventually, but it's also a matter of regional difference. I have Japanese honysuckle, and beat it back on the edge of the woods as it was doing too much damage to the woods, including the redbuds that ring my clearing and resumed their former spring glory when I beat back the honeysuckle. But I didn't get rid of the honeysuckle as I LOVE its scent. One year I realized it had crossed the clearing and was all over the copse on the other side, and tried to make a dent by ripping up the lacework of fine vines, hoping to at least have started the necessary eradication. To my surprise, that was it, it was gone the next year there. People talk about stiltgrass, and I don't get it--it's so easy to pull up, my definition of a "good weed," and you can just wad it up and use it as mulch. But I can see where it would be a problem if you farmed on a large scale. Wineberries--I deliberately planted a patch of those--the main negative is that I failed to eradicate autumn olive there first and have to keep snipping it out now. Wineberries are so pretty, and tasty. But they only bear once, while my red everbearing raspberries start in August and keep going until it frosts. The wineberries crossed the road in and established themselves in the copse aforementioned, and I wondered whether to get rid of them. But now that area is part of my
chicken run--the predators got so bad I gave up on free range and we fenced a run which includes the orchard, this bit of copse, and a bit of open area above the garden. I had thoughts or running cord through the tops of the fruit
trees and down to the
fence to confuse hawks--but then thought, why don't I try making a sort of food forest instead, planting forbs and bushes that won't shade the fruit trees but will hide the
chickens from above? I think, a couple more goumis, maybe some full dwarf fruit trees (that I can cover, as my next attempted solution to the squirrel problem), some wild sunflowers, chicory perhaps, more fennel, and as for the wineberries, all I have to do is not hinder their spread.