Muirburn: still generating more heat than light?

Last week, The Mirror newspaper waded into the acrimonious uplands conflict with a piece by its Environment Editor, Nada Farhoud. Farhoud reported that “campaigners say setting fire to the vital peatlands is creating an ecological disaster which also increases the risk of flooding and wildfires.” On the other side of the debate, Farhoud limited herself to saying only that, Gamekeepers claim muirburn is a “harmless way of boosting the bird population for an industry that is estimated to be worth £67m a year.”

This was a rather reductive characterisation of all the arguments made in favour of muirburn, but fairly typical of the monochromatic narratives we encounter so often these days in the news and across social media.

Actions and protagonists are good or bad; motives are good or evil; lines are drawn and the two sides, now established, are swiftly entrenched.

This urge to divide stems from a fundamental part of our natures – a desire to simplify, classify and box things off: something is safe or dangerous; edible or inedible; friend or foe. But while such dichotomies suit newspaper editors, may save time, and perhaps evolved to avoid the risk of catastrophically misclassifying something in the awkward grey in-between, the victims are nuance, understanding, and often truth.

And so, taking a deep breath, let’s get back to looking at muirburn. Defined as the intentional burning of moorlands to remove the top layer of vegetation, muirburn is actually carried out for a variety of purposes. It is used by gamekeepers to create the matrix of longer and shorter heather which yields the highest densities of grouse, just as Farhood reports, but it is also used by livestock owners and crofters to reduce stands of rank older heather and provide grazing opportunities on the fresh green shoots which emerge after fires; in some circumstances it can also be used to create fire breaks, or, in very specific and not uncontroversial cases, to promote peatland restoration.

However, muirburn should not, in theory, ever involve the burning of the peat itself, the substrate in which much moorland vegetation grows.

Consequently, when Nada Farhoud is captioned allegedly investigating “peat burning in the Yorkshire Moors”, muirburn’s advocates immediately bristle with resentment. So keen are defenders of muirburn to illustrate the harmlessness of a well managed “cool-burn” that they have created a series of videos, leaving first a Mars Bar and most recently an iPhone in the path of a managed winter burn, recovering these items after the fire has passed overhead and showing triumphantly how they have survived the passing flames unharmed.

These promotional videos are hardly scientific but illustrate their point well enough. The problem, of course, is that not all muirburn remains under control, or burns so coolly. A tragic demonstration of this occurred recently when a man lost his life after his clothes caught fire while he was burning heather. More commonly, the fires themselves burn out of control, perhaps more often today than ever before with crofting communities shrinking and less manpower available to manage burns. This trend undermines one of the key arguments made in favour of muirburn – that it reduces fire risk by reducing the fuel load which can otherwise build up on unburned moorland. Arguments over whether muirburn actually promotes or prevents wildfires present us with our first significant grey area, with the reality being that it likely does both, and I’d defy anyone to prove categorically whether the balance lies more towards causation or prevention. Werritty’s 2019 review recognised this when it stated that:

“Muirburns can potentially have both negative and positive effects in this respect. They can of course be the cause of wildfires if they get out of control, but they can also be used to reduce the risk of wildfires through reducing fuel-load build-up or acting as fire-breaks. Data sources from both Scotland and England are relatively few and quote varying proportions of wildfires starting from muirburns, and the levels of risk are currently difficult to quantify.

Werritty et al. 2019, Grouse Moor Management Review Group

Werritty’s review went on to report that, “out of 118 fires attended by SFRS, less than 10% of reported wildfires were attributed to ‘controlled burning’ or ‘heather burning’ (on any land, not just grouse moors), but larger numbers were reported as ‘other – not known’ cause.” How many of these fires were caused by muirburn is difficult to guess. A report from Natural England published in 2020 reported that 90% of upland fires had no recorded cause of ignition, but perhaps significantly, also reported that of those 10% where the cause was known, 68% arose from out of control muirburn. Furthermore, an unknown number of out-of-control management fires are brought back under control without ever being reported, with a 2003 questionnaire to 42 estate owner/managers suggesting that less than half the wildfires on their land involved call-outs to the fire brigade.

The picture is further complicated by the fact that moorland management, which often incorporates muirburn, is believed by some to make wildfires more likely, not just when planned burns getting out of control, but via the more general process of drying out peatlands and creating landscapes which become tinderboxes in dry weather. Certainly, if moors were left unburned for long enough, many of them would naturally become partially colonised by trees and develop into a mosaic of bog and deciduous woodland – the latter habitat so notoriously fire resistant that Oliver Rackham famously observed that “English native woods burn like wet asbestos”.

However, while there is much popular enthusiasm for rewilding these days and especially for letting nature do its own thing, the succession from managed moorland to established native woodland may not be a quick one. One fire ecologist told me that should we simply stop burning moors in the hope that a woodland may soon develop we will likely be disappointed. In the interim decades, biodiversity may well decline as heather and/or purple moor grass outcompetes other flora, and the risk of large, hot burns in this period will increase significantly. Should long stands of unmanaged heather catch fire, perhaps lit by a carelessly tossed cigarette or a thoughtlessly abandoned barbecue in one of Britain’s busy National Parks, the ensuing summer blaze would cause significant damage to underlying peat, potentially releasing far more carbon than any number of cool management burns.

On the other hand, with a little bit of judicious management, Norway’s reafforestation of its bare hillsides of 100 years ago shows what is possible and that change can happen surprisingly quickly…

Further controversy surrounds the issue of whether muirburn leads to a net loss of CO2, with fires releasing this greenhouse gas but subsequent growth and deposition of charcoal deposits potentially offsetting these losses. Indeed the evidence for overall losses was described by one review as “equivocal”. One study (part funded by the Heather Trust) suggested that burns every 20 years may actually create the best conditions for peat-forming mosses, while another non-randomized study claimed that areas burnt 8-10 years ago had up to 5 times more sphagnum moss than unburnt areas. Others suggest that the charcoal deposits left over from cool burns may serve to lock up carbon within the peat longer than any forest, where the carbon is often only temporarily stored, and where forestry management can turn plantations into carbon sources rather than carbon sinks.

Conversely, various other studies have suggested that muirburn may more often contribute to peatland degradation, reduce carbon storage within peat, and release toxic metals into the atmosphere, while an analysis of 95 peatland sites in the UK suggested that muirburn was damaging to sensitive plant species, resulting in less Sphagnum cover while reducing overall floral diversity by increasing heather cover. All these confusing and at times contradictory studies have been weaponised by the two sides arguing over the future of our uplands, those broadly opposed to or in favour of driven grouse shooting.

There are 3 main types of peatland in the UK: blanket bogs (which cover much of our uplands), raised bogs (relatively rare and discrete patches of raised bog, mostly found within agricultural landscapes in the lowlands), and fenland.

Pro-shooting organisations like the Moorland Association have been at pains to highlight the recent work of moorland owners in restoring blanket bogs, blocking old drainage grips and restoring patches of bare peat in eroded haggs, and have contrasted the work of grouse moor owners on blanket bogs with the state of England’s fens, claiming that 86 per cent of peatland emissions come from intensively cultivated lowland peat soils, where significant restoration is yet to start.

The Scottish Gamekeepers Association say muirburn has been “scientifically proven to provide many benefits” while the campaign group Gift of Grouse suggest that, “we can both have our cake and eat it“, provided only that burns are managed so as to limit their potential negative effects (reductions in peat formation) while maximising the gains muirburn can offer (benefits for some measures of biodiversity). The Game and Wildlife Conservation Trust summarised one study on this potential compromise, concluding that “burning approximately every 20 years would reach a balance that retains the benefits of carbon storage and peat growth, alongside increased biodiversity and reduced fire risk.” 

On the other side of the debate, anti-grouse shooting campaign group Revive, say that muirburn puts wildlife in danger and causes pollution to air and water, with smokey skies and water run-off full of organic content and heavy metals requiring expensive treatment to make safe for drinking. The campaign group Ban The Burn claim it increases flood risk for villages located below bare hill sides managed for grouse shooting. Revive also claim that, despite there being a presumption in the Muirburn Code against burning on deep peat, “research has found that 28% of all 1km squares subjected to burning in Scotland overlie deep peat, including many protected sites, and the annual number of burns increased significantly, 11% per annum, between 2001-2011.” More recently, they claim “independent research” has shown around 40% of land used for burning overlies deep peat. Unfortunately, Revive do not provide references on their website, although the first claim appears to originate from this paper, while the latter claim stems from a report commissioned by Revive.

So, what’s the answer?

Farhood seemingly received plenty of criticism from pro-shooting advocates following her article in The Mirror, but has since fired back that, when “the Climate Change Committee have recommended an immediate ban”, and when the “RSPB, Friends of the Earth and The Wildlife Trusts as well as the 53 other organisations that make up the Wildlife and Countryside Link – the largest environment and wildlife coalition – say the practice is damaging, surely it is time to listen.”

I suspect she is right. The UK Government has admitted that, amidst all the complexity, “There is a consensus that burning of vegetation on blanket bog is damaging to peatland formation and habitat condition. It makes it more difficult or impossible to restore these habitats to their natural state and to restore their hydrology.”

Natural England recognise a “moderate” balance of evidence suggesting that: i) burning reduces peat accumulation and reduces above and below ground carbon storage compared to no burning, ii) that managed burning can result in erosion and reduction in age level of the soil surface, and iii) that there are carbon losses through fuel consumption during burning and in conversion to char.

Nobody should pretend this is a straightforward issue, but increasingly, it is apparent that muirburn is carried out too often and across many habitats that are just unsuitable. Burning has been cited as a damaging pressure on 32% of the 76 dwarf shrub heath features and 24% of the 71 upland bog features present within Scotland’s Special Areas of Conservation. In the Cairngorms, observers have noted recovering juniper stands that have been burned.

At the very least, we need tighter controls over when and where muirburn may be permitted. In January, the English government announced new regulations that would “prevent the burning of any specified vegetation on areas of deep peat (classified there as peat that is over 40cm deep) on a Site of Special Scientific Interest that is also a Special Area of Conservation or a Special Protection Area unless a licence has been granted or the land is steep or rocky.”

If you thought that was all a bit hard to follow, you aren’t alone in thinking that. Campaigners were quick to point out that this would only create a very modest limit on current burning, with many grouse moors exempted because they either aren’t protected by any designations, or because they only lie on top of shallow peat. Consequently, none of the grouse moors in the North York Moors National Park face any new limits on when or where they can burn. And grouse moors that are not protected under any SSSI, SAC or SPA designation can of course still burn over any depth of peat they like.

To help monitor all this, the RSPB have now launched an interactive portal where you can report any burns that you see.

The English ban also does not apply on steep or rocky ground, which is puzzling because that exemption seems to be at direct odds with the Scottish muirburn code which specifies best practice should avoid burning on steep or rocky ground, because of the increased risk of erosion to steep ground after it is laid bare by burning, and because fires set in these environments are much harder to control.

Meanwhile, the Scottish Government has now announced plans to license all muirburn activity, but doubts remain here too, particularly around whether this new licensing regime will, like the new English legislation, contain too many loopholes to affect any significant progress. Currently, according to Revive, 40% of the moorland burned for grouse in Scotland overlies peat with a depth greater than 50cm. As recently as 2012, the RSPB reported that knowledge gaps made it “difficult to fully assess the costs and benefits of grouse moor management to biodiversity and the wider environment”, but today RSPB Scotland are campaigning for an outright ban on burning over peatland soils that extend over 30cm deep, in addition to a new licensing system for burning in other areas, so as to mitigate the risk to wildlife. It seems consensus may finally be emerging.

2 thoughts on “Muirburn: still generating more heat than light?

  1. Tommy's Outdoors April 9, 2021 / 8:42 pm

    Hi Hugh, this is a one great post! Thanks for writing it. I have definitely learned a bunch from it. A few questions/observations. I wonder what role the stands of rank older heather play in the ecology of the uplands. In other words, what is not happening ecologically with its absence due to burning. I noticed you mentioned crofting communities shrinking. I find this very interesting. A practice that is increasingly harder to maintain, to a high standard, due to socio-economical (I assume) circumstances. Another observation is that I see the obsession with what type of ecosystem stores more CO2. Unsurprising in many ways, but I think that if it comes to somewhat restoring the “wilderness”, that property of a ecosystem shouldn’t be the leading one in decision making. Personally, I do not like man induced burning of vegetation. When I was a kid in Poland, illegal burning of meadows and grasslands was a huge issue. It still is, decades later.


    • hughwebsterauthor April 10, 2021 / 9:22 am

      Hi Tommy – thanks for the comment. As I understand it, the older stands of long heather have an important role – not least as cover for nesting birds like hen harriers – but we should remember that muirburn on grouse moors does actually seek to maintain a mix of such long/rank heather with areas of newer growth. This may be less true where muirburn is used to facilitate grazing; I just don’t know. I think the “obsession” with CO2 is an important one, but take your point about valuing wilderness for its own sake. With regards to peatlands however, the two goals align very well. Currently, degraded peatlands emit three times more CO2 worldwide than all the intact ones absorb, so we need to restore this habitat on a global scale and turn it back into a net sink without releasing any more of the vast reserves of carbon currently locked up in peat. While muirburn may, in some circumstances, help promote peat formation – as I try to explain in the blog – the balance of evidence that I have been able to source suggests it is more often associated with overall harm to this habitat. It is also worth noting that healthy peatlands can naturally support some tree species but burning prevents their establishment. Plantations on peat can and do damage the peat by drying it out (a big problem in Ireland I believe), but natural colonisation of some damp-tolerant species like willows is probably harmless and creates a much more diverse landscape. Worryingly, our peatlands are drier now than at any time in the last thousand years, with this change linked to climate change and human activities, such as cutting, drainage, burning, and grazing, but the main driver is probably the warming of our climate. This means we probably need to work harder than ever to re-wet these habitats. The fact is that red grouse like dry moorlands better than wet ones, and so there is a conflict between what moorland managers would like the moors to look like and what healthy peatlands might otherwise look like. While there is some effort to re-wet areas of driven grouse moors, these efforts are probably not enough to cancel out the damage done elsewhere and burning likely contributes to a lot of drying in the UK.

      Liked by 1 person

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