Answer:
The effect of erosion depends mostly on one main factor- people. Left alone, land builds topsoil through complex ecosystems. there was no topsoil until fungi learned to metabolize minerals and, generally, the amount has only increased until humans begin to kill, remove, or change the natural life cycles in any given area. So, the answer to this question is completely relative to location and when thinking about top soil's depletion look no further than humans. Every piece of food that aay of us has ever eaten, has its roots either directly[plants] or secondarilly[meat] in top soil. Where does all of this incredibly important organic matter end up?- Down the freaking toilet. Please wake up to your effects on things around you, be responsible, and stop promoting the end of all life through consumer choices and life style CHOICES. Be smart, don't waste stuff.