Recreational trails reduce lichen and bryophyte diversity and the occurrence of rare species

Abstract Increasing recreational use of natural areas may pose a threat to biodiversity, particularly in sensitive high‐elevation ecosystems. Lichens and bryophytes (collectively termed cryptogams here) contribute substantially to biodiversity in almost all terrestrial ecosystems, but their response to disturbance from recreation has rarely been studied. We inventoried lichen and bryophyte communities and analysed impacts of disturbance and environmental variables at four study areas in Mount Rainier National Park, Washington, USA. The study areas ranged from low‐elevation, wet temperate forests to alpine environments and adjacent subalpine forests. A total of 77 liverwort taxa, 203 lichen taxa, and 195 moss taxa were found across all study areas, for a total of 475 cryptogam taxa. We found that cryptogam richness increased with increasing distance from trails across all study sites, even as far as 75 m from trails. Negative effects of visitor use on cryptogam communities appeared to be particularly pronounced in alpine areas. Rare cryptogam occurrences were associated with less trampled, wetter, and rockier sites in the alpine zone; we did not identify any drivers of rare cryptogam occurrences in forest areas. Synthesis and applications . Our results highlight that ecological impacts of recreational use may extend great distances from trails and other heavily used areas. Additional efforts by land managers to prevent visitors from walking off‐trail in heavily visited areas could help conserve lichen and bryophyte diversity.