Long-term climate warming is causing a bleaching effect in a key Arctic lichen species, according to new research led by researchers in the School of GeoSciences and British Antarctic Survey.
The study shows how rising temperatures are disrupting one of the Arctic's most important and widespread organisms, with potential consequences for fragile tundra ecosystems.
Lichens – symbiotic organisms formed by algae and fungi – play a vital role in harsh Arctic environments. They remove carbon dioxide from the atmosphere, provide food for herbivores such as reindeer, and support biodiversity across the tundra.
The research focused on the Arctic archipelago of Svalbard, one of the fastest-warming regions on Earth, where temperatures are rising up to seven times faster than the global average.
Researchers investigated how lichens responded to sustained temperature increases over nine years of experimental warming study. The team used plexiglass enclosures to simulate warmer conditions and monitored whether the lichens underwent bleaching – a visible loss of the algal symbiont and colour change linked to declining health and reduced photosynthetic activity.
A breakdown of symbiotic relationships through climate-driven bleaching is also well known in corals, where rising ocean temperatures cause corals to lose the algae they depend on to survive.
The study, published in the journal Functional Ecology, found that prolonged warming caused significant bleaching in the dominant lichen species Cetrariella delisei, reducing its ability to photosynthesise and grow. The findings suggest that this response may be driven by gradual, long-term increases in temperature, rather than short-term extreme weather events.
By analysing the results of the warming experiments the researchers showed that rising temperatures disrupt the balance between the fungal and algal partners that make up the lichen. Over time, this imbalance leads to reduced function and declining health, raising concerns about the future resilience of Arctic tundra ecosystems.
The findings are significant because the Arctic is warming faster than the global average, meaning even modest temperature increases can accumulate and push species beyond their limits.
The decline of lichens could have far-reaching impacts. As a dominant component of tundra ecosystems, they underpin food webs and ecosystem processes. Their loss could affect soil stability, nutrient cycling and the availability of forage for herbivores.
Researchers say the bleaching response could act as an early warning signal of ecosystem stress. Because lichens are highly sensitive to environmental change, they may provide an indication of longer-term impacts before more visible shifts occur.
Jiří Šubrt, lead author and PhD student from the School of GeoSciences, University of Edinburgh, said: "Our findings underline the importance of long-term ecological monitoring, mainly because slow-growing organisms such as lichens can take some time to respond to changes in temperature. The visible damaging changes illustrate that organisms that are thought to be resilient might be endangered."
