Climbing route development affects cliff vascular plants more than subsequent climbing: A guide to evidence‐based conservation management to regulate climbing

Cliff ecosystems provide refuge to 35%–66% of the world's endemic plants. However, they face growing threats from sport climbing. Evidence suggests that unclimbed cliffs harbour approximately twice the plant richness compared with climbed cliffs, with increasing impact as climbing intensity increases. Unfortunately, it remains unknown whether the climbing impact on cliff vegetation originates from the development (opening) of climbing routes or from temporal changes resulting from subsequent climbing. We recorded cliff vascular plants and lichens at the protected natural area of El Potrero Chico (Mexico) before and after the development of new climbing routes. Subsequently, we re‐recorded the routes at sequential timepoints after 10, 20, and 30 ascents. Additionally, we examined whether the abundance of cliff vegetation influences the extent of climbing impact and whether the surroundings of the routes were also affected. We found that the opening of climbing routes exerted the strongest negative effects on cliff plants, reducing species richness by 38%, while subsequent ascents generated a minimal impact. Worryingly, route opening affected not only species richness in the route itself but also the surroundings of the routes. After 30 ascents, cliff plant abundance decreased by 60.6% within the bolted routes, whereas it decreased by 42.3% in the surroundings. However, this impact depended on the original cliff vegetation abundance. Lichen cover showed a gradual decrease, indicating that cliff‐dwelling lichens are affected not only by the opening of the route but also by subsequent ascents. Synthesis and applications: Given the almost non‐existent regulation of outdoor climbing activities in most countries, we urge the implementation of a conservation management protocol that defines clear strategies to regulate climbing activities and preserve pristine cliffs. On yet unclimbed cliffs with narrow endemic, rare, or threatened species, we propose banning the establishment of new climbing areas. On climbed cliffs lacking protected species, dynamic management actions should be implemented, such as setting a maximum number of routes that can be established and defining limits of acceptable change as climbing intensity increases. The proposed conservation management should help to halt the loss of unique cliff biodiversity and safeguard pristine cliff ecosystems. Our study shows that the climbing‐related activity with the strongest impact on cliff plant communiti