While it stands to reason that rock climbers might harm habitats such as the ancient, stunted forests that grow on cliffs around the world, there has been little unambiguous evidence that this is so. Now, the first study to isolate rock climbing from other factors confirms that the sport damages cliff ecosystems.
“Our work shows that rock outcrop ecosystems suffer dramatically when exposed to recreational rock climbing,” says Douglas Larson of the University of Guelph in Ontario, Canada. This work is presented in the April issue of Conservation Biology by Larson and Michele McMillan, who is also of the University of Guelph.
Rock climbing popularity has soared in North America over the last 20 years, disturbing areas that had been untouched. However, previous studies on the ecological effects of rock climbing have been contradictory.
McMillan and Larson studied the ecological effects of rock climbing on vegetation (vascular plants, bryophytes, and lichens) on the heavily climbed limestone cliffs of the Niagara Escarpment, which is near Toronto in southern Ontario. These cliffs have the most ancient forest east of the Rocky Mountains, with eastern white cedars that are more than 1,000 years old. The researchers compared the vegetation on three parts — the top edge (plateau), the middle (cliff face), and the base (talus) — of climbed and unclimbed cliffs.
The researchers found that rock climbing greatly decreases the diversity of vegetation on cliffs. Climbed faces had only four percent of the vascular plant species found on unclimbed faces. Moreover, the diversity of bryophytes and lichens in climbed areas was roughly 30 and 40 percent of that in climbed areas, respectively.
Rock climbing also decreases the vegetation cover on cliffs. For vascular plants, the cover on climbed plateaus and talus was roughly 60 percent of that on unclimbed areas. For bryophytes, the cover on climbed plateaus and talus was about a fifth of that on unclimbed areas. Although climbing did not affect the extent of lichen cover, it did change the types of species that grow on cliffs. Delicate lichen species were replaced by tough ones: in unclimbed areas the most common lichens are so fragile that they crumble to the touch, whereas in climbed areas the most common lichens are so sturdy that they can even withstand rubbing.
McMillan and Larson also found that in climbed areas, the proportion of nonnative plants was three times higher than that in unclimbed areas. Climbing reduces plant density, thus increasing the number of sites where nonnative plants can grow. Furthermore, climbers can introduce seeds and living pieces of nonnative plants via their shoes, clothing, and equipment.
To help protect cliff ecosystems, McMillan and Larson recommend banning new climbing routes in protected areas along the Niagara Escarpment and explaining why. “Recreationists are far more likely to abide by management plans when they are aware of the ecological rationale behind the restrictions,” say the researchers.
For more Information
McMillan, M.A. and D.W. Larson. 2002. Effects of rock climbing on the vegetation of the Niagara Escarpment in Southern Ontario, Canada. Conservation Biology 16:389-398.