Towards an understanding of future range shifts in lichens and mosses under climate change

Aim: Lichens and mosses play important functional roles in all terrestrial ecosystems, particularly in tundra and drylands. As with all taxa, to maintain their current niche in a changing climate, lichens and mosses will have to migrate. However, there are no published estimates of future habitat suitability or necessary rates of migration for members of these groups at the global scale. 

Taxon: Lichens and mosses. L

ocation: Global. 

Methods: Using global occurrence data, we conducted ensemble distribution models in the ‘biomod2’ R package, parameterised with a range of climatic, land use and soil variables, to estimate current and future (2100) habitat suitability in 16 abundant species of lichen and moss. 

Results: Without considering dispersal limitation, suitable area was forecast to expand for eight species and decline for four species. For species with predominantly boreo-arctic distributions, suitable area typically declined at the temperate range edge and expanded across the High Arctic. Future suitable area available to dryland-adapted species generally declined overall, likely relating to the desiccation-tolerant physiology of lichens and mosses. The average migration rates required for species to disperse into new suitable habitat ranged from 1.7 (Placidium squamulosum) to 9.0 km year⁻¹ (Syntrichia ruralis), although most species will need to migrate >16 km year⁻¹ to completely fill their potential future suitable habitat. 

Main Conclusions: For mosses and lichens, as with all species, migration will be an important part of the adjustment to a warmer climate, but realisation of these potential migrations will require both rare dispersal events and habitat that is suitable in non-climatic dimensions. Current evidence on dispersal in these groups suggests that these geographical shifts may be unlikely to be realised without intervention, especially in landscapes that are highly modified by humans.