In the latest issue of New Scientist it is claimed that, "Rock climbers do not, after all, damage the ecology of cliffs and routes they scale." This statement is based on recent research by Kathryn Kuntz and Doug Larson at the University of Guelph, Ontario. Earlier studies on the Niagara Escarpment, a popular limestone climbing area, claimed that climbers did effect the vegetation on the cliffs they climb on. This research was cited by land managers in the US when placing restrictions of cliffs and gave climbers a bad reputation amongst conservationists. This more recent study found fatal flaws in the earlier research - that the scientists had neglected to test whether cliffs that climbers chose to climb actually had more vegetation to begin with. Or rather researchers had chosen cliffs that were steep and generally devoid of vegetation in the first place and had used this simple fact to come to the conclusion that climbers had destroyed the vegetation.

Nick Colton, deputy chief executive officer of the British Mountaineering Council was quoted in the New Scientist report, he said, "Climbers would always choose solid stone cliffs over plant-covered ones."

You can read some of the report at the New Scientist website