Guest blog by Jess Allan (MSc Conservation graduate, UCL and Science & Research Project Manager, The Tree Council)
Peatlands are critically important wetland ecosystems, storing more carbon than any other land-based habitat, helping to store and slowly release water, and providing vital habitat for birds and other animals. Peatlands also harbour weird and wonderful plant species such as Sphagnum mosses, and carnivorous Sundews.
Round-leaved sundew, a charismatic peatland species (c) Andy Hay (rspb-images.com)
Despite their importance, many peatlands have been degraded by human activity, including being drained for large-scale peat mining, forestry, and agriculture. This turns peatlands from carbon stores into greenhouse gas emitters, exacerbating climate change. To safeguard our future, and give nature a chance to recover, we therefore must protect and restore these habitats.
An international collaboration
Large areas of peatland are currently being restored. Nonetheless, this work arguably lacks a strong scientific basis, as our understanding of how vegetation, the cornerstone of functioning peatlands, responds to different restoration approaches, has remained limited. Also, studying peatland restoration involves getting your feet wet and hands dirty, but when a global pandemic strikes, you have to find a way to do conservation science from a desk!
Because some restored peatlands have been well studied and the results published in scientific journals, we can use this information to look for general patterns of the response of peatland vegetation to restoration.
For our study, conducted by a team of researchers from UCL (myself and Jan Axmacher), the RSPB (David Douglas) and the Peatland Ecological Research Group (PERG: with Mélina Guêné-Nanchen and Line Rochefort) based in Canada that we recently published in Restoration Ecology, we reviewed and analysed the existing evidence, aiming to improve our understanding of the effectiveness of peatland restoration techniques. We interrogated the existing studies to investigate how quickly characteristic plants recover when different techniques are used.
This ‘meta-analysis’ involves combining data from multiple existing studies, and then examining it to identify any overall trends. We focussed on temperate peatlands (i.e. excluding tropical peatlands) and were interested in all types of restoration approach – from low or no intervention, to active reintroduction of plants. We reviewed previously published studies and gathered data relevant to our research questions. In total, our final dataset covered 275 sites where peatland restoration has been attempted, represented by 5929 data points. These were mostly from sites in North America, Western Europe, and Scandinavia.
How quickly can peatland vegetation recover?
We tested how quickly peatland vegetation responded to three types of action to restore peatlands, which we categorised into three groups: passive, standard/basic, and enhanced techniques.
We found that passive restoration – where no intervention is made beyond stopping any ongoing causes of harm – generally gives very little certainty that peatland vegetation cover will return to a ‘natural’ state. It is important to note that these are overall trends, and passive measures may well be appropriate in very specific scenarios; it likely depends on how damaged the site is and whether there are propagule sources nearby. This emphasises the need to have a good prior understanding of the site to inform the restoration works.
‘Standard techniques’, which include blocking drainage systems to ‘rewet’ a site, were projected to deliver vegetation resembling an intact peatland after 45-55 years. . Finally, enhanced measures, specifically active revegetation, were seen to accelerate recovery, delivering Sphagnum mosses resembling an intact peatland after 30-35 years, and 20-25 years when we included other specialist peatland plants. In short, active revegetation appears to restore peatland plant cover around ten years faster than standard techniques. With regards to restoring the diversity of plant species, our study indicates that enhanced measures once again perform better than other approaches.
What does this mean for peatland policy and practice?
Peatland restoration is urgent – to turn these ecosystems back into carbon sinks, we need their plant communities to recover. Based on our findings, passive techniques seem unlikely to provide timely and reliable results except in very favourable conditions.
Standard intervention approaches such as rewetting are popular and likely form a large proportion of current peatland restoration activity. Their advantages include their lower upfront cost, but it appears that, on their own, they may not maximise the rate at which peatland can be restored.
Active measures such as revegetation appear to offer a route for the most rapid recovery of peatland vegetation. These measures are likely to cost more, require more people power, and crucially a sustainable supply of vegetation such as Sphagnum moss. But if they accelerate the rate of recovery, they should be taken into consideration by policy-makers, funders, and practitioners.
Our work also highlights the essential role of monitoring and publishing the outcomes of peatland restoration. This evidence can allow us to continually improve and learn how to maximise the effectiveness of restoration, especially as climate change may make conservation and restoration more challenging.
A bright future for peatland restoration
To me, the research has also emphasised the complexity of natural systems, and the challenges we face in trying to reverse the damage inflicted upon these precious habitats. Nonetheless, I also feel uplifted by the passion, drive, and expertise that is so evident in conservation scientists! I have no doubt their efforts will support the recovery of many bogs and fens, so they return to being healthy, resilient and teeming with life.
The need for peatland restoration has also been recognised by policy-makers, for example in August 2023 the UK government invested £16m in 12 new peatland restoration projects. This is fantastic to see, and I hope to see a focus on using this money in the right way and ensuring that there is support for monitoring and adapting to new evidence.
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