I don't think the issue is so simple to relay on propaganda statistics.
How many negligent ATV riders will it take to make another Great Canyon?
I live next to protected water-sheet on desert.
Lot of signs, chains, cables, concrete barriers, yet lot of ATV drivers "don't see" all those warnings.
Did it create a problem over the years? Evidently not. Maybe in 1000 years, but do I have to worry about it?