Yeah, my town is pretty bad right now, it's getting so that I can't even roll a decent snowman. If this is indeed a programming error, I hope Nintendo will fix it! It would be great if we could get a nice covering of grass/snow everytime it rained/snowed. That would make sense, how grass grows with a little rain, and well, there is more snow after it snows.
One thing I've noticed is that I have a hill in town I have dubbed 'Red Cosmos Hill' because it's completely covered with red cosmos. Well the desertification of that area completely stopped after I planted all those flowers even though I use that hill daily. So I am hoping/thinking that extreme flower coverage will stop any grass loss. It might be that you have to have 1 spot, plus the 8 spots around it all covered with flowers just to get the spot in the middle to stop losing grass.
Anyway, now that my museum's fossil collection is complete I don't have to walk all over town every day fossil hunting. So for the past two days I have been avoiding that hill and area in general because I want to see what it looks like after a week, to see if any grass/snow has grown back. Hopefully the amount of flowers, plus having my environment in perfect condition will speed up recovery. If that's the case then I'm going to start marking off bits of my town to avoid and let the environmental recovery begin.