I know you can walk on shards when there's no monsters on them, but the game currently doesn't let you attack monsters that are sitting on shards. I'm sure we can dispatch them without harming the shard, and if we get an updated version where this is allowed, it would allow me to save a shard that has only 1 skerrick left. 
Otherwise, there will have to be a lore reason, but I would prefer if you can remove those monsters from where they're not wanted. 
