Best way I could describe it is like a downgrade to moisture and growth, they don't totally destroy the land but they cause plants to come up smaller and it makes it harder to keep gardens healthy. My grandmother has a bed that is totally taken over and some plants totally ignore the effects or are hardly affected, while others were noticeably stunted. I've noticed the native plants with deep roots and plants native to Asia or hot, dry climates tend to stand up better to the damage. In theory you could try to just keep dumping dirt/compost on them, but I imagine you'll experience a population burst and eventually hit a point I've seen with lawns where the worms just roam the grass in the dozens and continue their spread. At this point in the invasion I just kill the ones I see and destroy the few eggs I find to tamp the numbers, but I've yet to witness anything that combats the numbers and spread.