Climate change impacts on blanket peatland in Great Britain

Peatland restoration has been suggested as a key method for the UK to meet national, legally binding climate targets. This can involve blocking up drainage ditches or erosion features, as well as encouraging regeneration of peatland vegetation through Sphagnum reintroduction or removal of scrub or trees. It is unclear, however, how suitable future conditions will be for both peat accumulation and Sphagnum survival. We applied three bioclimatic envelope models for blanket bogs in Britain to assess how future climate is likely to deviate from current conditions, focussing on four national parks with significant peatland area (Dartmoor, the Flow Country, the Peak District and Snowdonia). We also assessed the likelihood of thresholds being passed at which irreversible desiccation of Sphagnum moss may occur. Our bioclimatic envelope models use updated climate projections (bias-corrected UKCP18 projections under Representative Concentration Pathways (RCP) 2.6, 4.5 and 8.5) that are more accurate in the upland regions in which blanket bogs can occur, and use thresholds of blanket bog occurrence which are tailored to Britain. This gives us higher confidence in the results as compared to previous models. Our results show substantial losses in areas suitable for peatland by 2061-2080 under all RCPs. Under RCP8.5 there is virtually no peatland within its current bioclimatic envelope in our case study areas and only limited areas in Snowdonia under RCP4.5, suggesting these regions will be outside the ideal conditions that lead to peat accumulation. Only western Scotland retains substantial areas suitable for peat. The frequency of Sphagnum desiccation events is projected to increase by between 44% and 82% which will likely result in decreased success of hummock forming species, particularly at easterly sites where rainfall is lower, though wetter microsites will likely allow more drought-tolerant species to persist. Policy implications. Action should be taken to raise water tables at degraded sites to limit the impact of future drought conditions. However, climatic conditions being outside the current bioclimatic envelope may make full restoration challenging. Sphagnum reintroduction programmes may have greater success utilising drought-tolerant species as hummock forming species are at greater risk of die off during desiccation events.