In Finland, one in four lichen species is classified as threatened, and the share has nearly doubled between the national red list assessments of 2010 and 2019. Lichens are part of one of nature's most successful symbioses and represent a significant portion of Finland's evolutionary heritage. About 20% of the country's threatened lichen species grow in subarctic habitats, yet the ecological requirements of these organisms remain poorly understood. For most groups of microlichens found in the region, assessing their threat status is currently not possible due to basic gaps in biodiversity knowledge.
Rapid warming in the Arctic, proceeding at nearly four times the global average rate, has shortened snow cover duration and altered habitats across the north. Snow plays a complex role: it insulates lichens and supplies meltwater during dry periods, but it also limits photosynthesis and shortens the growing season. As tree lines advance and forests change, these shifts are reshaping subarctic ecosystems in ways that are not yet fully understood.
Lilith Weber is a researcher at the Faculty of Biological and Environmental Sciences, University of Helsinki. Her doctoral work focuses on subarctic lichen diversity and the environmental factors shaping lichen communities, with fieldwork carried out at the Kilpisjärvi and Kevo research stations in northern Finland. The dissertation consists of three journal articles. In the first, Weber reviews the current state of knowledge on climate change impacts on lichens in subarctic and alpine ecosystems. In the second, she links complete epiphytic lichen datasets from two localities in northern Finland to microclimatic measurements and satellite imagery at fine spatial scales, using statistical modelling to identify the environmental factors that shape species distribution and community structure. In the third, she documents previously undescribed biodiversity within crustose epiphytic lichens in the Finnish subarctic, illustrating how much remains to be discovered even in areas that are considered relatively well studied.
The findings demonstrate the value of detailed, fine-scale research for conservation. Identifying the habitat, substrate, and climate characteristics associated with high lichen vitality is a practical prerequisite for designing effective conservation or restoration measures.
- The imminent risk of lichen diversity loss means that while it is important to acknowledge the complexities involved, recommendations based on the current state of knowledge can and should be made, Weber writes in her concluding remarks.
Much of the research draws on fieldwork at two subarctic field sites in northern Finland: Kilpisjärvi and Kevo. Both stations are part of the nationwide network of university research stations, which provides researchers with long-term infrastructure and local expertise across Finland's diverse environments. Without this network, fine-scale ecological datasets of the kind central to Weber's work would be difficult to collect and maintain.
The Kilpisjärvi region represents one of the most important subarctic lichen habitats in Finland. Weber has also contributed to the Kilpisjärvi Science Trails application, where a webinar recording from February 2023 introduces lichen diversity and the ecological significance of the area to a broader audience.
The thesis "Subarctic lichen diversity - effects of climate change and snow" was defended by MSc Lilith Weber at the Faculty of Biological and Environmental Sciences, University of Helsinki, on Friday 24 April 2026. Dr. Rebecca Yahr, Royal Botanic Garden Edinburgh, served as opponent and Prof. Jouko Rikkinen as custos.
A lichen species new to science, Lecanoropsis prolificans, was formally described in 2024 based on specimens from multiple locations, including Pikku Malla (69.054171, 20.764048) on the forest slopes towards the lake. Although the publication was not included in the dissertation, the find is worth noting for Kilpisjärvi: material collected from Malla contributed to the original description of the species.