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 harbor approximately twice the plant richness
compared to 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
time-points 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.