Living on the Edge: Rock climbing changes plant communities on cliffs

Cover photo Source: Rock Climbing El Chorro Spain, youtube.com

SOURCE: Lorite, J., Serrano, F., Lorenzo, A., Cañadas, E. M., Ballesteros, M., & Peñas, J. (2017). Rock climbing alters plant species composition, cover, and richness in Mediterranean limestone cliffs. PloS one, 12(8), e0182414. https://doi.org/10.1371/journal.pone.0182414

Want to see one of the least disturbed and least well-understood ecosystems around the world? You may not have to travel far. Cliffs are found in nearly every country and have shaped the agricultural and industrial development of entire landscapes. But despite being widespread, they have remained largely inaccessible to both scientific researchers and the general public.

That is, until recently.

In the past 50 years, the popularity of rock climbing has increased more than that of almost any other outdoor activity. As a result, cliffs that had never been directly impacted by humans are receiving increasingly high levels of traffic each year. Each climb can cause a small amount of damage by trampling or pulling out plants, and these impacts add up as climbers use the same routes over and over again. It’s hard to say exactly how much the cliff ecosystem will be affected because the dangerously steep slopes that had kept tourists off of cliffs have also typically kept researchers away.

This year, a research team from the University of Granada stepped up to the challenge. Specifically, the team aimed to discover the impact of rock climbing on the plant communities situated on cliffs. They picked sampling locations, set up some ropes, and sampled in the easiest way they knew how: they rappelled!

Man rappelling down a cliff
Rappelling involves setting up a rope at the top of a cliff and slowly lowering yourself down. Source: thrillophillia.com

As the group traveled down the cliffs, they took photos of the vegetation in areas that are used for climbing as well as in nearby areas that aren’t used by climbers. They ultimately traversed 34 transects and photographed over 400 sample sites. Using a computer program, they analyzed the photos to find out which species are present in each area, which area has the most plant cover, and which area has the greatest number of species.

A Growing Pattern

As they predicted, areas that are used for rock climbing had fewer plant species. Areas frequented by rock climbers also had a lower percentage of the rock surface covered in plants, and they had different species present than in the unclimbed areas. However, this effect wasn’t uniform across all sites. Areas that were climbed very frequently had the most severe changes, and areas that were only climbed occasionally were not affected as severely.

Teucrium rotundifolium flowers
Teucrium rotundifolium (Source: Biodiversitdad Virtual)
Melica minuta (Source: flora.org.il)

Four plants, in particular, were very strongly affected by the presence of rock climbers. Chiliadenus glutinosus, Melica minuta, Rosmarinus officinalis, and Teucrium rotundifolium were commonly found in unclimbed areas but rare when subjected to stressors from climbers.

For folks who enjoy rock climbing, these results may not come as a huge surprise; rock climbing takes a toll on the cliff plants at all steps of the process. To establish a route, climbers must “clean” or “garden” the path by trampling andpulling out many shrubs and other plants. Later on, trees and sturdy bushes will be used to support ropes, which wears away at the plant over time.

This environmental toll is especially significant in light of the other environmental stressors that could be acting on cliff ecosystems. Mountainous regions are especially sensitive to climate change and could be losing important native species at an accelerated rate. For another great envirobites article about a human-caused change in mountain ecosystems, check out this recent post about plant species richness on mountain summits.

Onwards and Upwards

Inspired by their results, this research team has outlined a management strategy for their home country of Spain that will help minimize environmental damage from rock climbing.

Right now, very little is known about the specific ecological importance of each climbing area around Spain, so the team recommends beginning with an assessment of all existing climbing routes. This assessment would determine the impact each route has on threatened species and important geologic features. If a route poses a specific threat to rare or endangered species, managers should recommend closing the route. If not, they should assess if it needs limitations such as a set climbing season, limited capacity, or restricted routes. A similar review is necessary for all new routes that are proposed.

As climbing intensity increases, it’s important that scientists keep up. Studies like this one are critical because they help ensure that we will have the knowledge we need to effectively manage cliffs: historically one of the least disturbed and least studied ecosystems worldwide.

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Abigail Lewis

I am a fourth-year undergraduate at Pomona College with interests in limnology, microbial ecology, and nutrient cycling. In between rehearsals, hikes, and long dinners I am working to build a career that will address environmental issues and build a more inclusive scientific community.

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