I was in college starting in 82, and I worked in the same town after so I lived there from 82 to 93. It just so happens that was about the time mountain bikes really started to take off.

There was a falls with a drop of 100 feet on private property. The owner's family had allowed the public in for over 100 years, including students, etc. It was a long drive and a mile's walk to get there, but it was a pretty popular picnic and hiking spot.

I use as my erosion gauge a plastic drainage pipe that ran across the main path which was just barely poking out of the bare dirt in 1982 when I got there. In 1986, when I first started seeing mountain bikes back there, I'd guess there had been MAYBE 1/4" of erosion in the previous 4 years. By 1988, just 2 years later, there were mountain bikes on that path CONSTANTLY and the pipe was now hovering 2 feet over the path, which was now a gully carved into the landscape, so the bikes were now making new paths, all of which were eroding extremely fast.

Within another year, the owners fenced the area off due to the landscape being torn up, and now nobody can enjoy this beautiful area. Yes, I certainly do blame the mountain bikers.

I'm sure there are mountain bikers who respect the landscape, but there are those who don't, and it doesn't take many of them to do more damage than all the hikers put together.