Threats on Lichens and Their Conservation—A Review Based on a Bibliometric Analysis

Lichens, symbiotic associations between fungi and photobionts, are essential and sensitive bioindicators of environmental change. Despite their resilience, lichens face increasing threats from air pollution, land-use change, unsustainable harvesting, and climate change. This study presents a bibliometric analysis of global research on lichen threats between 1981 and 2024, using data from Scopus and Web of Science, combined with an additional analysis based on the database Recent Literature on Lichens (RLL). A total of 319 research publications were analyzed through VOSviewer (version 1.6.20) and Biblioshiny (R core team version 4.5.2) to assess temporal trends, thematic evolution, authorship, and geographical distribution of affiliations, and 1354 publications from RLL were studied for frequent authors and geographical distribution of study sites. Results show that research output was initially dominated by air pollution studies (1981–2004) but shifted after 2005 toward conservation and climate change impacts, with a sharp increase after 2017. North America and a few European countries led in scientific production, while biodiversity-rich regions in Africa, South America, and Southeast Asia remained underrepresented. Despite increasing publication trends, collaboration remains moderate (23% international co-authorship), and many threatened species remain unassessed. Recovery measures emphasize habitat protection, improved forest management, pollution control, integration of lichens into global biodiversity frameworks, and enhanced international collaboration. This study provides a systematic overview of how lichen conservation research has evolved, suggesting strategies for decelerating lichen diversity loss under accelerating global change.