Outdoor bouldering is a popular sport in which people climb on natural rock. However, this has a negative impact on the vegetation and the surface structure of the rocks, a study shows. Climbing erodes mosses and lichens at the holding points and releases microplastics. The researchers therefore advocate limiting bouldering to certain zones and times in order to protect the sensitive ecosystems of the rock faces.
Bouldering is a popular climbing sport that has experienced rapid growth in recent decades. More and more athletes around the world are active in this discipline – indoors and on natural rock. That’s why more and more rocks are being developed into climbing areas. But what consequences does this sport have for the environment? How does outdoor bouldering affect the ecosystems around the climbing areas and the habitat of animals and plants directly in the rock crevices and on ledges?
Researchers led by Isabell Österle from the University of Bayreuth have now investigated this. To do this, they carried out experiments on three rocks made of different rocks: limestone in Franconian Switzerland, granite in the Fichtel Mountains and sandstone near Bayreuth. The team climbed these previously untouched rocks 500 times each time, regularly taking photos of the climbing route. They then compared how the growth of mosses and lichens on the stones had changed.
Microplastics instead of mosses and lichens
The result: After the climbing passages, up to 15 percent fewer mosses and lichens were found on natural footholds in the rock. The handles, however, showed significantly less or no erosion. The plants and fungal-algae communities suffered the most damage during the first ascents of the routes. The porous sandstone proved to be particularly vulnerable and showed more signs of wear than limestone or granite. The vegetation damaged during bouldering and the resulting disrupted microbial diversity only partially recovered within three years, as later control tests on the sandstone showed. “The effects of bouldering vary depending on the type of rock. The ecosystem recovers only slowly,” summarizes co-author Sofie Paulus from the University of Bayreuth.
During their experiments, the researchers also took rock samples and examined them for microplastics using spectroscopic methods. In fact, they were able to demonstrate for the first time that when the rubber soles of climbing shoes wear, black plastic particles and rubber additives are transferred to limestone. “Bouldering introduces microplastics directly into sensitive ecosystems and could have an impact, among other things, on the microbial community,” explains senior author Manuel Steinbauer from the University of Bayreuth. The plastic particles are also considered potentially harmful to human health and many other living beings.
Stricter rules for outdoor bouldering needed
Particularly worrying: The plastic pollution and plant abrasion occurred after moderate use of the natural rocks without any other aids. “Even without the use of climbing chalk or the usual sport practice of cleaning the rocks before the first ascent, we have already been able to document the effects of bouldering on natural rock,” says Paulus. These methods increase the athletes’ grip on the rock, but also damage the ecosystem – due to greater erosion and because the magnesia changes the pH value of the subsoil, as the team explains.
The researchers still don’t want to ban bouldering completely. However, in view of their findings, they advocate differentiated management strategies that create a balance between recreational use and nature conservation. For example, they propose to only allow climbing in certain zones and in alternating locations. The idea is that some rocks would not be allowed to be climbed at all, while others could only be climbed temporarily and could recover in between. This would help protect sensitive ecosystems and also preserve rare plant species in rock crevices. In addition, apps could be introduced through which climbing athletes document their routes and thus help conservationists monitor the environment.
Follow-up studies with more data and from other areas should now clarify how much microplastics end up in the environment during bouldering and whether other plants or communities are also threatened.
Source: University of Bayreuth; Specialist article: People and Nature, doi: 10.1002/pan3.70207