A seemingly benign hobby is causing some unintended environmental consequences, according to a new study from the University of Bayreuth. 

What's happening?

German researchers found that climbers engaging in bouldering are not only rubbing off delicate lichen and mosses during their ascents. They're also eroding the stones and leaving microplastics in their wake. 

The study examined the impact of 500 climbs on natural limestone, granite, and sandstone surfaces. It found that up to 15% of lichen and moss was lost in handholds and footholds. 

"Our study is the first to demonstrate that the impact of bouldering varies according to rock type and that ecosystem recovery is slow," said report author Sofie Paulus. "Moreover, our experiments highlight an overlooked issue: microplastic pollution from climbing shoes." 

Why are boulders important?

While big rocks might seem infinitely durable and benign, they play key ecosystem roles. For example, stones in the Norwegian wilderness allow vegetation to grow in soil that would otherwise erode. Tourists overturning those stones has diminished that opportunity and disrupted reindeer migration, which depends on foliage. 

This is doubly challenging as lichen and moss grow quite slowly. It takes a long time to make up for this kind of vegetation loss. Introducing microplastics to the mix could further slow that recovery. 

"Bouldering therefore introduces microplastics directly into sensitive ecosystems, which could affect, among other things, microbial communities," said co-author Manuel Steinbauer. 

When microplastics wash out into water supplies, they can also end up in our food and introduce health risks when ingested. 

What's being done about bouldering?

While the majority of the world's microplastic problems come from clothing and paint, understanding how even unassuming activities impact the natural world can help curb damage. 

Common bouldering conventions such as cleaning the rock prior to an ascent have only served to exacerbate the issue, according to the study. Researchers recommended that certain handholds be left untouched for a period of time so vegetation would have a chance to recover.

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