Establishing the Potential Future Extent of the Scottish Rainforest Using Species Distribution Models and the Indicator Species Lobaria Pulmonaria

Abstract

The Scottish temperate rainforest is regarded as an important habitat, restricted to rare climatic conditions. The diverse populations of epiphytic lichens situated in West Scotland allow the region to be characterised as a temperate rainforest. Climate change in Scotland threatens the survival of the Scottish rainforest. This study investigated the impact of climate change on the potential spatial extent of the Scottish rainforest through the use of an indicator species, Lobaria Pulmonaria (L.pulmonaria). Using a Species Distribution Model (SDM) ensemble, the WorldClim bioclimatic variables and climate change scenarios, the future extent of the Scottish rainforest was predicted by the probability of the occurrence of L.pulmonaria. The models were evaluated using k-fold cross-validation. High-performing models produced Area Under Curve (AUC) of the Receiver Operating Curve (ROC) scores greater than 0.5. The outcome of the future projections suggested that the extreme climate change scenarios will result in the severe restriction or potential elimination of the Scottish rainforest. The most likely scenario, Shared Socio-Economic Pathway (SSP) 2.45 suggested that the L.pulmonaria populations will favour the conditions in North Scotland and the Western Isles. This indicated that the current conservation measures in place through both the Woodland Trust and the Forest Habitat Networks are in the appropriate locations according to future climate change predictions.