I'm pondering and muttering thoughts out loud, spewing nonsensical factoids if you like, here before heading out on an early morning in an early heatwave. I wonder how they get to that 20%... Is that after one infestation of the 5 big species on the move or is that after all 5 have moved in.. But as it's all we've got what would that do i wonder? It will take mulch longer to break down. It will still happen... But slower. Do they eat smaller ones? I think they might hunt smaller ones first. Will the earthworms learn to fight back? How about some earth worm Krav-Maga course this summer.. (joke) Don't the bigger worms eat a bigger percentage of the mulch? Then it makes not such a big dent.
I guess there is nothing we , a few thousand Permie minded folk can do against them. Compost and plants keep on getting imported. And once in, they have up to 3 generations a year, they're hermaphrodites and some can even split themselves. Aliens... The RHS said plant swaps are another cause of the spread.
They'll take their place in the ecosystems i guess whatever we do. Maybe we should look at it this way, preventive plant more pioneer species of trees to up the leaf litter bio mass in anticipation of them arriving. I'm doing an experiment with aspen trees this year. I found a little grove and have gone in in autumn and ripped out some root to propagate. It's sprouting beautifully and i'll incorporate it into edible food hedges/wind blocks i'm installing.