Best Practices

Mitigating the Effect of Rock Climbing on Cliff Ecology

By Felipe Morales-Armijo & Martí March-Salas

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Key lessons

• Learn about each cliff’s unique biodiversity

• Be aware of the impacts of rock climbing on cliff organisms

• Avoid producing physical damage to cliff organisms

• Practice caution when using climbing chalk

• Consult biological experts before opening new routes

• Follow sustainable climbing practices

About the authors

MSc. Felipe Morales-Armijo is a PhD student at the Universidad Autónoma de Nuevo León (Mexico) and a climber from Chile. His passion for adventure sports and traveling guided Felipe to begin his professional development as an expedition and ecotourism engineer. After working as a park ranger in Chilean Patagonia, Felipe’s sense of ethics and love for conservation fueled his motivation to learn about the impact of rock climbing on cliff vegetation. This motivation led him to dedicate his graduate master thesis to researching these issues. Felipe is currently helping climbing communities understand the impact of rock climbing on cliff vegetation and promoting the conservation and protection of these ecosystems.

Dr. Martí March-Salas is a Postdoctoral Researcher and Principal Investigator at the Goethe University, Frankfurt (Germany), as well as a recreational climber. His research focuses on understanding plant evolutionary processes and population dynamics when faced with climatic changes and anthropogenic pressures. He leads international projects investigating cliff ecological processes, which are fragile landmarks that serve as a refuge for many different rare and unique organisms. In these projects, he focuses on potential human and environmental impacts on plant communities, in addition to the role of abiotic and biotic factors on plants’ adaptation to extreme cliff conditions.

Peer reviewer

Georgia Harrison

Editors

Angela Cecil, Ludivine Brunissen

About the best practices project

The Global Climbing Initiative's best practices project taps the expertise of climbing leaders around the world to share lessons learned in crag development and maintenance, environmental conservation, equity and inclusivity, community engagement, economic impact, and climbing organizations. By making this information more accessible, we hope to foster a more united and supported global climbing community. To learn more about this project and how you can support, visit globalclimbing.org/best-practices

Introduction

Cliffs are rock formations that are almost vertical—a feature that makes them ideal for climbing. They are globally distributed and can be found near the sea, high in the mountains, or within forests or other terrestrial ecosystems (Larson et al. 2000; National Geographic). Individuals around the world can recognize spectacular rock formations such as the impressive Cliffs of Moher in Ireland, the huge Kapaupapa Cliffs in Hawaii, the popular Preikestolen in Norway, the white Étretat Cliffs that surround the French coast, the extravagant pinnacles of Mallos de Riglos in north Spain, or the sheer granite rock face of El Capitan in Yosemite. Many of us have gazed at these cliffs for hours, but we rarely pay attention to the unique biodiversity they harbor. This is probably because cliffs’ living organisms may be hidden to the naked eye, or they seem insignificant compared to the cliffs’ greatness

Despite remaining undisturbed by humans for much of history, cliffs are now facing a growing threat from the increasing popularity of rock climbing over the last 30 years. Climbing has shifted from a niche sport only practiced by a few to a worldwide sensation. For instance, in the late 1990s, there were less than 500,000 climbers in the US, but more recent reports estimate that this figure has grown exponentially to approximately 10 million climbers (American Alpine Club [AAC], 2019). Overall, the number of climbers worldwide has increased at a rate of 15-20% per year, with some estimates ranging up to more than 50 million climbers (AAC, 2019; deCastro-Arrazola et al., 2021). This popularity can lead to overcrowding on cliffs and increased climbing use, especially after the COVID-19 outbreak, after which many people aimed to reconnect with nature.

On top of that, the profile of the recreational climber has evolved. Previously, climbers commonly sought to connect with nature by engaging in a sport they loved and occasionally tested their limits on unexplored routes (American Alpine Club [AAC], 2019). This implied a leisurely enjoyment that promoted mental and spiritual well-being. This climber profile still holds true, but other climbers have different goals and aspirations. This is evident from the increasing number of climbing gyms (e.g. in 2021, 591 new climbing gyms were opened in the USA; American Alpine Club [AAC], 2019). Currently, many climbers may be less experienced with outdoor climbing and have a limited understanding of the idiosyncrasies of the cliff system. Additionally, more experienced climbers seek physical challenges, which may involve opening new routes, getting the first ascent, or setting speed records (American Alpine Club [AAC], 2019). Therefore, today’s rock climbing is not just a leisure activity. Now, it is a sport whose popularity will continue to increase, especially since its debut as an Olympic sport in 2020, which will also increase potential impacts on cliff biodiversity (deCastro-Arrazola et al., 2021).

In this chapter, we aim to make you, as climbers, aware of the wonderful biodiversity of rocky outcrops and to show how we can take collective action to achieve a sustainable balance between climbing and biodiversity conservation.

Key Lesson #1

Learn about each cliff’s unique biodiversity

Cliffs are biodiversity hotspots, and contain a unique collection of species. Many living organisms that inhabit cliffs are unique, and their disappearance from the cliffs we climb could have an irreparable impact.

Cliffs have remained poorly investigated from an ecological point of view. This lack of research is due in part to their inaccessibility. However, each cliff can contain important biodiversity and be of high conservation and ecological value, since they carry unique species which are not usually present in neighboring terrestrial ecosystems. Cliffs harbor diverse life forms, such as arthropods, gastropods, reptiles, amphibians, bats, emblematic birds, bryophytes, lichens, or unique and rare plants (Larson et al., 2000; Fig. 1). Furthermore, some of the species that inhabit cliffs are internationally recognized for their rarity and threat status, which make them conservation priorities. For instance, cliffs in Canada can support more than 40% of faunal species considered to be of high conservation value (Sinnemann, 1992). In Oregon and Washington (USA), more than 60% of amphibians and reptiles live in cliff habitats (Larson et al., 2000). As a climber, you also probably know that cliffs support an abundance of bird species, since they are ideal places for nesting far from predators. In fact, some cliff-dwelling birds are critically endangered or endangered species, such as the California Condor or the Peregrine Falcon, which are declining in number due to habitat degradation and human disturbances. This further supports the idea that cliffs are a key habitat for many species.

Cliffs also provide vital climatic and ecological refuges for many different plant species (Fig. 1) (deCastro-Arrazola et al., 2021). In fact, the plant diversity of some cliffs can be even greater than that of other nearby regional ecosystems, such as forests, scrubland, or grasslands (March-Salas et al., 2023). This is partially due to the abundance of different features for plants to inhabit, such as crevices, fissures, ledges, and terraces. These features create microhabitats with little but sufficient soil and especially humid temperature conditions that support microorganisms vital for the growth of certain plants (Kuntz & Larson, 2006; Krah & March-Salas, 2022). Many of these plants are endemic, rare, and even endangered species (Fig. 1). The loss of endemic species would represent the extinction of these particular plants since these species only inhabit specific cliffs and are not able to survive in other ecosystems. For instance, it has been reported that cliffs harbor 35-40% of endemic taxa in Europe and up to 66% in New Zealand (Larson et al., 2000). Cliffs are also the homes of millennia-old trees. It was recently discovered that a Juniperus population from a cliff face on the Canary Islands (Spain) includes the oldest known living tree in the European Union, which is approximately 1,481 years old (Sangüesa-Barreda et al., 2022).

We hope this data shows to you that altering this ecosystem, even slightly, can be much more ecologically impactful than in other natural areas. Therefore, as a climbing community, we have to be aware that our activity, although wonderful in many ways, can also cause an irreparable impact to wildlife.

Key Lesson #2

Be aware of the impacts of rock climbing

Regrettably, even when taking precautions, climbing can damage cliff fauna and flora. Let’s try to be aware of the potential impacts that we can create because this will help us to be less harmful to cliff ecosystems!

The impacts of climbing on cliff biota are multifaceted and include, among others, (i) removing vegetation from cliff faces during route opening, maintenance, or ascent; (ii) the disturbance of cliff-dwelling animals that may abandon these habitats if they feel threatened; (iii) visual and aesthetic effects caused by the use of climbing chalk and bolting; (iv) the trampling of vegetation in the cliffs’ surroundings; or (v) the erosion generated on the cliff face itself due to the removal of mosses, lichens, or algae during repeated ascent (Fig. 2).

Ecological research into the impact of rock-climbing on cliff vegetation is sparse, but when present, there is clear evidence that climbing has an impact on cliff biodiversity. Early studies comparing biodiversity in climbing areas versus unclimbed cliffs showed a notable decrease in the abundance of herbaceous plants and trees (Nuzzo, 1995; Kelly & Larson, 1997). Recent studies used more robust methodologies confirming that, in addition to lower abundance, climbing decreases plant species diversity, threatens many rare plants, reduces genetic diversity (which is key for the future survival of certain species), and decreases biological associations — all of which affect the composition and survival capacity of cliff plant communities (Vogler & Reisch 2011; Clark & Hessl, 2015; Lorite et al., 2017; March-Salas et al., 2018; Harrison et al., 2022; March-Salas et al., 2023). Additionally, climbing decreases the presence of lichens and mosses (Zaniewski, 2012; Clark & Hessl, 2015; Boggess et al., 2017; Harrison et al. 2022), and poses a threat to cliff-dwelling bird communities (Covy et al., 2019). The latter includes changes in the behavior of some emblematic and endangered bird species, such as reduced foraging and singing behaviors in overcrowded climbing sites (Covy et al., 2020).

All the climbing impacts mentioned above, however, do not indicate that sustainable climbing is not possible, or that climbers do not seek to respect cliffs’ and their surroundings. In fact, many climbers likely started climbing partly because of their love for nature and outdoors. Nevertheless, to reverse this trend and halt biodiversity loss in cliffs, the climbing community needs to implement urgent sustainable actions.

Key Lesson #3

Limit physical damages to cliff organisms

Many times we unconsciously remove plants during climbing, or remove soil and seeds accumulated in crevices for greater safety during our ascent. Let's practice safe but respectful climbing that promotes cliff biodiversity!

In some areas, temporary climbing restrictions are in place for seasonal raptor nesting. However, cliff flora is largely unprotected. As mentioned before, it is already well-recognized that climbing negatively affects diverse plant communities by lowering the number of plants that grow on a climbing route and its surroundings. These effects can come from uprooting and clipping plants during the opening of the route and also during climbers' ascents. In fact, it has been shown that a higher climbing requency affects cliff plants exponentially, showing that more climbers lead to a greater impact on the cliffs and its surroundings (Clark & Hessl, 2015; Lorite et al., 2017). Furthermore, the use of metal brushes to remove mosses and lichens is very common, as well as removing felled trees in the middle of the climbing route. These types of actions are usually referred to as "route cleaning" and alter cliff ecosystems. For instance, mosses and lichens provide substrate and nutrients to the cliff plants and generate microenvironments for pollinators such as ants. Therefore, these actions should be minimized for the wellbeing of the cliff environment.

In addition, “route cleaning” frequently involves removing the soil accumulated in rock crevices in order to prevent substrate from decreasing our grip. However, this soil is a potential environment where a new plant could grow. For instance, some specialist plants have the incredible strategy of orienting their flowers towards rocky walls, which increases the chances of seeds falling into a crack on the rock face. In this sense, the soil that we remove for safety reasons may contain seeds that would become future plants.

Finally, the impacts of climbing on cliff flora also depend on climbing intensity and difficulty. It has to be considered that first ascents could be more impactful to cliff plants, such as lichens (Schweizer et al., 2021). Harrison et al. (2022) found that differences between climbed and unclimbed areas’ biodiversity were greatest on routes of lower grades because they received more traffic and often have more crevices where diverse plants can be established. So, route difficulty and frequency of ascents are also aspects that should be considered.

Key Lesson #4

Practice caution when using climbing chalk

Climbing chalk is a magnesium carbonate that can harm cliff wildlife and generate clear visual impacts on rock faces. Let’s try to lower its use!

While the direct physical damage of climbing is certainly obvious, the visual and chemical impacts of rock climbing on cliff biodiversity, through the use of climbing chalk, remains unknown. Climbing chalk is used by climbers to get a better grip. It is a powder with sweat-absorbing properties made from magnesium carbonate (MgCO3). Normally, climbing chalk is white, which contrasts with the color of most rock formations. Climbers usually deposit a small amount of magnesium on the rockface, which accumulates over time and eventually causes an aesthetic impact from its overuse (Li et al., 2001; Çetinkaya et al., 2021). To diminish the visual impact of its use, some companies have created products that could better simulate the color of the rocks, but these chalk substitutes are not yet fully established commercially and still contain chemicals.

Chemically, the pH of cliff soil might be increased by the addition of climbing chalk (Hepenstrick et al., 2020), which may affect plants and soil microbiota (Krah & March-Salas, 2022). We understand that mentioning soil microorganisms may seem surprising, but microbial organisms help plants to uptake nutrients from the soil which promotes their longevity (Krah & March-Salas, 2022). As a carbonate (MgCO3), climbing chalk could increase the soil’s pH where cliff plants grow and alter soil microorganisms which are very sensitive to changes in pH. In addition, climbing chalk usually creates a layer of debris on the soil surface that acts as a crust affecting the moisture and texture of the cliff soil by drying it out. Therefore, the addition of climbing chalk can directly and indirectly affect plants’ establishment and development. In fact, a unique study testing the effect of climbing chalk on cliff organisms has found that it decreases the germination and survival of cliff-dwelling ferns and mosses (Hepenstrick et al., 2020). However, this study was carried out on siliceous cliffs (which have an acidic pH) with species less adapted to carbonates such as the plants inhabiting limestone cliffs. So, the effect of the climbing chalk may depend on the type of rock. Understanding this concern, it is important to reduce the use of climbing chalk and even start to consider natural and non-chemical-based alternatives for climbing.

Key Lesson #5

Consult biological experts before opening new routes

It is likely that the greatest impact on cliff biodiversity occurs during the opening of new climbing routes. Let’s contact local climbing organizations and qualified biological experts before acting!

Cliffs have been highly overlooked in conservation agendas, with very few regulations controlling rock climbing in most countries. As the popularity of climbing continues to grow, a deep-rooted problem has yet to be addressed: the increased opening of new climbing routes and the appearance of new climbing areas in remote and protected areas. For instance, in northwest Spain, one of the only six populations of Petrocoptis grandiflora, an endemism of limestone outcrops (Fig. 1), was almost eradicated due to climbing. The origin of this nearly irreparable ecological footprint relies on the lack of a prior in-depth assessment of the potential impacts of new routes on biodiversity, denoting insufficient regulatory control on cliff habitats.

This point is pivotal for effective cliff protection because the greatest impact likely occurs during the opening of a new route. In addition, route equippers frequently remove plants and mosses to facilitate climbers’ ascent. Ideally, this action should be prohibited, and equippers should rather select among the many areas where plant and moss removal would not be necessary for safety reasons. Identifying in advance the presence of species with high conservation value is also essential. Therefore, to define the ecological limits that cliffs can support and whether an area is appropriate for climbing, best practices indicate that biological experts, nature managers, and local climbers must collaborate and assess the territory before opening new climbing routes (Fig. 3).

Key Lesson #6

Follow sustainable climbing practices

We all have the power to make decisions that can help foster harmony between climbers and the crags where we recreate. Let’s take simple but efficient actions to promote sustainable climbing!

There are several practices that you (as a climber, climbing guide, outfitter, nature or sport lover who climbs from time to time…) can consider for improving the sustainability of your climbing:

1. Avoid trampling plants on the way to climbing areas by staying on established trails and not taking short-cuts off-trail. Also, preserve the ground at the base of the rock face by using it only for belay and rope management. Walk and stand on durable surfaces.

2. Check local regulations and build relationships with local experts before opening new routes. Biologists can be incredibly helpful in determining the sensitivity of the flora in a climbing area, helping you assess the best location for new routes.

3. Metal brushes are highly impactful on cliff flora, and their use should be minimized as much as possible. Consider alternative locations for a climbing route if the one you had in mind would require large-scale removal of lichen, moss, or other vegetation.

4. Try to observe the cliffs’ wildlife. It is not always easy to find, but it can be fascinating!

5. Do not remove the soil accumulated in cracks. Perhaps there is a nearby climbing hold that doesn't need that cleaning.

6. Clean your shoes and ropes carefully before climbing (preferably at home), as they can hold unwanted species such as alien plants.

7. Take care of the placement and movement of your rope. The friction of the rope against cliff plants can damage them, affecting their reproductive traits and even uprooting them.

8. Minimize the use of climbing chalk and try to look for natural substitutes of the same color as the rock.

9. If you are a climbing guide, please inform your students about these sustainable practices at the start of the course.

Conclusion

Cliffs are complex ecosystems that are highly sensitive to human presence. Given the current climbing boom, which will continue to grow in the coming years, conservation of existing biodiversity on cliffs is more important than ever. Cliffs hold organisms that would not survive in other ecosystems, so their protection is vital for their long-term conservation. Cliff protection is, however, possible if we implement science-based regulations and if we consider the points of view of different stakeholders.

To promote sustainable climbing, it is essential to follow the next three actions: First, learn about the uniqueness of cliff habitats or boulders where we climb. Each cliff contains amazing biodiversity, and we must comprehend more in depth what exists in the rock formations where we climb. Second, be aware of the current worrying situation of rock climbing’s impact on cliff biodiversity and how we can reduce our impact as much as possible. Third, create collaboration between route developers, climbers, biologists, and local authorities to create best practices appropriate to your specific environment. Assessments for opening new routes would serve to show areas with low conservation value where rock climbing will have low or no impact on local biodiversity. If the described actions are rigorously implemented, we will be able to significantly reduce the loss of biodiversity in cliff ecosystems while enjoying this beautiful sport. Sustainable climbing is possible if we all—climbers, scientists, and authorities—work together in the same direction through education and collaboration.

References

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