Jonny Ritson talks us through the latest modelling study, conducted alongside colleagues, aiming to determine how suitable future conditions will be for both peat accumulation and Sphagnum survival in the UK.
Bioclimatic envelope models have been used as a tool to map the climate conditions under which specific habitats occur. By defining the conditions suitable for peat formation, for example, we can then use projections of future climate to see how this envelope of suitable conditions might shift or shrink in the future.
The study
Our new analysis shows that the envelope under which blanket bog formation occurs will virtually disappear in England under most realistic future climate projections. While pockets remain in Wales and Scotland, there are still large reductions in the area over which suitable conditions are likely to occur. The Flow Country, for example, despite being in the far north of Scotland, could see a reduction in suitable conditions of between 53 – 68% under the mildest climate change projections or 77 – 87% under the projections more likely to occur given current emission pathways. Only in western Scotland do we see a large-scale continuation of conditions favourable for blanket bog formation.
Additionally, we also modelled the risk of Sphagnum moss die-off events caused by droughts and found this is likely to increase by 44-82% in the future. Sphagnum is considered a keystone genus for peat formation and has been the subject of intense reintroduction programmes throughout UK blanket bogs. Our results focussed on the hummock forming species which are most at risk from drought, and therefore suggest that there may be a shift in prevalence as the more drought tolerant species adapted to living in ‘hollows’ on the bog are more likely to survive. This could have implications for species selection in reintroduction schemes and make the goal of the ‘hummock-hollow’ microtopography considered characteristic of UK blanket bogs difficult to achieve in many areas.
What will happen to UK peat?
This is not to say that UK blanket bogs will simply disappear. Peatlands are, to an extent, resilient systems which have feedback processes that limit the impact of drought, heatwaves and other unfavourable conditions. Even in a completely degraded state, as we have seen in the Peak District where intense pollution from the Industrial Revolution killed off vast areas of peatland vegetation, it can take hundreds of years for significant amounts of peat to be lost.
What our results show is that climate conditions are going to be increasingly challenging for peat formation. Action to increase the resilience of peatlands is needed as quickly as possible before the worst of climate conditions manifest themselves. The dire projections in our analysis could potentially make this easier, however. Climate finance initiatives, such as the UK Peatland Code, generate money for restoration by selling carbon offsets based on avoided emissions from a ‘do nothing’ scenario. Our results suggest that the ‘do nothing’ scenario could be much worse than previously thought, meaning more finance may be available.
Next steps
There is still plenty more to do to understand the resilience of these systems, however. The most pressing question is ‘what does it really mean to be outside the bioclimatic envelope?’. We know that lowered water-tables brought about by drought and drainage typically lead to the loss of carbon from peat, but at what rate will it be lost and what can we do to limit this?
Current restoration efforts have been successful in halting erosion and bringing back vegetation to areas of bare peat but what does future success look like if we no longer have the climatic conditions which created these landscapes in the first place?
Read the full article “Climate change impacts on blanket peatland in Great Britain” in Journal of Applied Ecology.
