Also just an idea. How about movelock-ing the person that depletes a resource, making him unable to leave the scene of the resource for some time based on how much he depleted that resource.
Lest say when he gathers below 50% he is movelocked for 1 hour,
33% - 3 hours,
20% - 6 hours,
10% - 12 hours.
Rather then some form of skilldmg(witch i honestly doubt will make ppl consider NOT depleting again) this should effectively stop the depletion of a resource and if not stop ppl from depleting several location all in 1 day.