Rock climbing affects cliff-plant communities by reducing species diversity and altering species coexistence patterns

Abstract

Cliffs are unique ecosystems with an outstanding but relatively unknown plant diversity, harboring rare, endemic and threatened species, but also rock-specialist or generalist species that can become locally common and dominant on cliffs. The rising popularity of climbing represents an increasing threat to cliff biota, affecting community composition and potentially diminishing diversity and species associations. We used a novel sampling design of closely-paired climbed versus unclimbed points along the cliff-face. We sampled along climbing routes of different climbing intensities in El Potrero Chico (Nuevo León, Mexico), identifying plant species and analyzing species associations and community composition in climbed and unclimbed plots. Diversity on the sampled cliffs was high, even greater than in other regional ecosystems. We found reduced abundance, cover, and diversity in climbed plots, irrespective of climbing intensity. Dominant species on the sampled cliffs were the most negatively affected by rock climbing in terms of abundance, and some locally rare species, including endemics and endangered species, were entirely absent from climbed plots. Co-occurrence analysis showed that the number of associations between pairs of dominant and common species were greatly reduced in climbed plots, and that positive associations between locally rare species existed in unclimbed plots but not in climbed plots, which may contribute to the disappearance of endemic and threatened species. Finally, NMDS analysis revealed that the community composition changed significantly due to climbing. Our results indicate that conservation science should convince stakeholders of the need for a holistic conservation of cliff ecosystems and not focus solely on emblematic or rare species, since plant community dynamics and preservation depend on interactions between plant species.

Origin of the impact of rock climbing on cliff ecosystems: A guide to evidence-based conservation management to regulate climbing

“…Furthermore, our study provides a new interpretation of results from previous studies on this topic. Our findings on the effect of route opening within and in the areas close to the climbing routes suggest that the climbing effects previously found in other studies with closely-paired designs showed conservative results (e.g., Clark and Hessl, 2015;Tessler and Clark, 2016;Boggess et al, 2017;Reding, 2019;March-Salas et al 2018, 2023b. The climbing impact found in these studies should then be primarily attributed to the repeated climbers' ascents rather than to the opening of the climbing route, which is clearly the bottleneck of the detrimental process.…”

“…To assess the strength and the origin of the climbing impact, we used a case-control design with a 3 m wide × 3 m high quadrat positioned at three zones of the climbing route (see March-Salas et al 2023b). The quadrat consisted of: a central plot of 1 m width and 3 m height representing the central area of the climbing route (so called 'within the climbing route'); two immediately adjacent surveyed plots of 0.5 m width and 3 m height, as this area could be potentially used by climbers during their ascent, and therefore would not be exempt from being disturbed; two plots 1 m far from the center of the climbing route of 0.5 m width and 3 m height on the left and right sides of the 3 m × 3 m quadrat that served as controls, representing areas not reached by climbers and outfitters (so called 'near the climbing route').…”

“…Given the uniqueness and high conservation value of cliff biodiversity, understanding the threats of rock-climbing and developing approaches for an effective conservation management is imperative (deCastro-Arrazola et al, 2021). There is consistent evidence that rock-climbing negatively impacts species richness and abundance in cliff habitats, also catalysing a significant decline of rare plants (e.g., Tessler and Clarck, 2016;Lorite et al, 2017;March-Salas et al, 2018;Schmera et al, 2018;March-Salas et al, 2023b).…”