Burning peatland and the complexity of socio-ecological systems

Back on the 14th January this year George Monbiot published an article in the Guardian entitled ‘Meet the conservationists who believe that burning is good for wildlife’ see here.


He argued that burning (also known as swaling on Dartmoor) is bad for wildlife as it destroys habitats and stops scrub and trees from growing. George had previously been on Dartmoor the previous October where he was invited to address the UK National Parks at their biennial meeting – he talked about re-wilding, how the moors of the UK had been ‘sheepwrecked’ and why he thought swaling was a bad idea – you can watch his talk here.

Burning as a management tool has been used on Dartmoor for over 8000 years – it was the burning of the forest by Mesolithic Man and the subsequent grazing that followed that has in part created the cultural landscape that we know today. Tom Greeve has published a historical review of swaling on Dartmoor – see here and you can also download a report of a training day  held on Dartmoor between English Nature and the National Trust in 1998 here.

In March Monbiot was further incensed as a paper ‘The role of fire in UK peatland and moorland management: the need for informed, unbiased debate‘ (see here) which was to be published by the Royal Society in May unexpectedly got into the public domain. The paper criticised Monbiot’s article on swaling on Dartmoor – in addition the ‘leaked’ paper was hijacked by a group called ‘You Forgot the Birds’ which had been set up by pro grouse moor advocates to attack the RSPB. He responded to the paper in an article entitled ‘Bonfire of the Verities’ – see here. What a muddle and how ironic!

Well, on the 16th December the same group of authors who wrote the original paper have published a second one to address the issues raised by Monbiot in March. That paper is titled ‘Informed debate on the use of fire for peatland management means acknowledging the complexity of socio-ecological systems‘. You can download that paper here. It is definitely worth reading. I have provided the abstract of the paper below.

The effects of fire and its use on European peatlands and heaths are the focus of considerable research and debate due to the important services these ecosystems provide and the threats they face from climatic and land-use change. Whilst in some countries ecologists are actively promoting the restoration of historic fire management regimes, in the UK the debate has become increasingly acrimonious. Positions seem entrenched between continuing the intensive form of management associated with grouse moors or ceasing burning and seeking to eliminate fire altogether. In a recent paper we argued that participants’ positions appeared influenced by political and philosophical beliefs associated with, for example, private land-ownership, hunting, and associated conservation conflicts such as raptor persecution. We also suggested there was inadequate engagement with key concepts and evidence from fire and peatland ecology. We argued that management debates should aim to be inclusive and evidence-based, and to understand the benefits and costs of different fire regimes. In a strongly-worded critique of our paper, George Monbiot (author of “Feral: Searching for Enchantment on the Frontiers of Rewilding”) suggested we: i) framed our research question too narrowly; ii) made the implicit assumption that moorlands were the “right” ecosystem for the UK countryside; and iii) failed to adequately engage with arguments put forward for cessation of managed burning. Here we critically examine each of these issues to provide further insight into how adaptive, participatory land-management could develop. We argue that a productive debate must acknowledge that complex trade-o s are inevitable during ecological management. Choosing the “right” ecosystem is difficult, especially in a landscape with a long history of human influence, and the answer depends on the values and ecosystem services we prioritize. Natural resource management decisions will be improved if based on an understanding and valuation of the multiple scales and levels of organization at which ecological diversity exists, the role of disturbance in controlling ecosystem composition and function, and the need for participatory action.

I suspect Monbiot will pen a response to this paper.

Monbiot’s January swaling piece in the Guardian also included my data of heather and blanket bog deterioration in the Plym Valley in south west Dartmoor. The authors of the second paper say of this ‘we would suspect the inappropriate combinations of burning and grazing are more likely to be to blame than the use of burning as part of the management system per se’. I would agree with that.

The original May paper is very focused on the northern heather moors where fire is being utilised to manage heather to encourage high density populations of red grouse. It addresses issues such as the severity and frequency of burns but it doesn’t talk about the timing of burns – on Dartmoor swaling can be carried out as late as the 31st March by which time some moorland ground nesting birds have already got nests.

On Dartmoor swaling is used to manage heather, gorse and particularly purple moor grass (Molinia caerulea). Unfortunately the paper makes no reference what so ever to Molinia which is now a major problem in many upland areas. It has spread into heather communities and has become dominant. Molinia is palatable to cattle in the late spring and early summer but after that it is generally avoided and the autumn it has turned white creating huge areas of what Ian Mercer described as ‘rafia’.

Much of the swaling on Dartmoor now is used to burn off the ‘rafia’ in an attempt to produce flushes of palatable grass the following spring. These new flushes of grass growth attract in the grazing animals both sheep and cattle. This practice in the past led to intensive grazing in these areas which led to the reduction of heather which I referred to in the Upper Plym.

Trying to re-establish heather stands in these Molinia dominated grasslands has proved to be very difficult. It has also been established that if Molinia is burnt and then not grazed heavily the following spring by cattle the abundance of Molinia is likely to increase. On Dartmoor today the numbers of cattle have reduced considerably and in most areas where Molinia is burnt the grazing intensity by cattle is now not great enough to reduce it and indeed may be encouraging it.

It is not burning alone that is responsible for the spread of Molinia, since the 1900s  the aerial deposition via rain of nitrogen (from cars, industry and agriculture)  has resulted in critical loadings in the uplands. On Dartmoor between 1989 and 1992, 93.3% of one kilometre squares received nitrogen deposition above the critical threshold. The various nitrogen compounds deposited are fertilisers and encourage plant growth. It is widely acknowledged now that Molinia responds aggressively to increased levels of nitrogen while heather on the other hand does not. If we add global warming into this mix, carbon dioxide levels have now risen to over 400ppm from 260ppm prior to the Industrial Revolution and the average global temperature has increased by over 1 degree. Enhanced carbon dioxide levels promote plant growth when there is sufficient soil nitrogen – in the uplands today there now is sufficient nitrogen, whilst it has yet to be proven it is reasonable to speculate that increased temperatures and increased carbon dioxide levels will promote the increased growth of Molinia.

I would like to have seen something about fire and Molinia in the paper, especially as one of the authors is a world authority on Molinia and its control.





9 thoughts on “Burning peatland and the complexity of socio-ecological systems

  1. One would expect nitrogen deposition on Dartmoor to be further enhanced by high ground-level ozone concentrations combined with the frequent occurrence of hill fog in contact with the ground. This is just one of many reasons why it’s astonishing that urban air pollution control often neglects the impact of pollutants on the generation of ozone hundreds of kilometres downwind. The contribution of similar mechanisms involving sulfur have been extensively researched in contributing to the catastrophic deterioration of Eastern European upland forests in the 1990s. Let’s hope that similar ecosystem collapse attributable to local factors interacting with oxides of nitrogen is not on the cards for Dartmoor. (https://www.research.manchester.ac.uk/portal/en/publications/observations-on-great-dun-fell-of-the-pathways-by-which-oxides-of-nitrogen-are-converted-to-nitrate-vol-28-pg-397-1994(f5ed3136-f9f8-4996-b3d4-78681defaefc).html)

    • Thanks for this Roy – I am aware of the ozone research but the studies relating to its impact on plant growth are contradictory – some say it enhances growth some say it inhibits it. A recent piece of work demonstrated that high levels of ozone in hay meadows suppressed flowers but enhanced the growth of grasses. Unfortunately I can’t access your link yet I will try again when I get on my University computer

      • …just make sure wet deposition of nitrate isn’t forgotten – in an attempt to simplify the problem it’s tempting to focus on the impact of each individual pollutant on an ecosystem. One would hope the pH of Dartmoor hill fog would be close to 5.6 nowadays, but put 50 ppb of ozone and 15 ppb of nitrogen dioxide into it and you can easily make millimolar concentrations of nitric acid, and maybe a factor of 10 to 100 higher if the fog droplets are small – In the years since I worked on this, the deposition rates ought to have been quantified a bit better and it should be easy enough to find experts still working in the field who could give clearer answers on the extent to which acid deposition could damage Dartmoor in today’s pollution climate, including which mechanisms are dominant. The direct impact of ozone on plants wasn’t an area I worked on, although I shared an office for a few years with some members of the research group who I recall were having some fun trying to measure its deposition velocity so I’m not surprised if the evidence on impacts is tricky to interpret!

  2. Thanks for your great coverage of our paper Adrian I’m glad to know you agree in at least some places. You’re certainly right that we didn’t cover everything here. I do certainly agree with you regarding the issues with Molinia control, that’s a very important restoration challenge and you’re right that it demands more attention. As you suggest there has been some interesting research on the topic suggesting fire can play a role in increasing encroachment though I’d like to see more on how fire and grazing interact.

    We probably did have a northern UK bias in our paper partly as so much of the public discourse is clouded by issues associated with grouse moor management. I wish we’d had the space to talk more about the issues faced by moors and heaths in the South-West and South-East, and how fire can be used in other upland ecosystems, they’re certainly complex and deserving of attention. We’ve touched on some of these in a previous paper a while back: http://www.tandfonline.com/doi/abs/10.3843/Biodiv.4.3:1

    You’re also right that we need better information about how the timing (seasonality) of burning affects both floral and faunal responses to fire. We’ve been pressing the need for UK research to more specifically focus on the concept of “fire regimes” for a while now – that would include understanding how variation in intensity, severity, seasonality and spatial patterning of fire affects ecosystems both on its own and when interacting with other disturbance regimes such as nutrient deposition and grazing.

    • Matt – thank you for taking the time to reply. I like both of your papers!

      I have worked in conservation in the UK for 35 years and have now decided to study for a PhD – I’m at the LEEP Institute at Exeter University http://eprofile.exeter.ac.uk/adriancolston/ which is in the Politics Department. In am originally an ecologist who study my BSc at Exeter and an MSc at UCL. My PhD is about why it is so difficult to find consensus on the Commons of Dartmoor. Thus I found your almost social science approach in both papers very interesting.

      The Monbiot intervention on Dartmoor has been profound and has driven a wedge between a consensus that was (very slowly) coming together. Your papers make an important contribution to this debate – cultural landscapes or rewilding?

      I guess my comments on your papers were based around the fact that you were ‘hijacked’ by a discussion of burning on peatlands on Dartmoor when your work focused on peatland and moorland in the North which are subject to grouse shooting and therefore you had the potential to miss some the nuances of the situation in the south west (as you will know the majority of uplands research has been conducted in the ‘north’ and not the south west.

      One of the reasons that I have mentioned Molinia, nitrogen, carbon and I could have mentioned ozone is that the research seems to suggest that overgrazing and inappropriate burning regimes combined with atmospheric pollution appears to have changed the nature of the uplands irreversibly BUT no one seems to be saying that and as a result conservation policy and objectives carry on as if nothing has changed.

      Best wishes

      • Totally agree and to be honest some of the fault there is mine as a result of where my radar is at. Much of my own experience comes from Scotland and northern England rather than say the Pennines or where N deposition has had very substantial effects (or at least well documented compared to my neck of the woods). I think you’re spot on that it’s all to easy to make generalisations across whole ecosystem whereas in reality there is significant regional and local variability in the drivers of change. That’s one of the points we’ve tried to make regarding the need to understand the effects of interacting, varying disturbance regimes even if we had a northern bias. I totally agree about folk happily ploughing on as before in their established paradigms and one of the reasons we argue for an Adaptive, ecological use of fire. Excellent stuff, Adrian – do keep me posted on how your PhD develops!

  3. I’m surprised you say
    “On Dartmoor today the numbers of cattle have reduced considerably …”
    Reduced compared to when?
    I am just an interested layman but from my observations as a Dartmoor resident I would have said that cattle numbers have increased noticeably in the last few years and it has been sheep numbers that have reduced. I was led to understand this was related to the lifting of the export ban on beef.
    Are you just simply talking about longer time scales then me and how does the recent apparent increase affect your argument if at all?

    • You are right Colin – I haven’t been that clear. On one hand I was referring to the past when thousands of South Devons and other breeds were summered on the moor – the so called Red Tides. After the Commons Registration Act of 1965 these lowland farmers lost their rights to summer any animals on the moor. There then followed a period when headage payments were made which encouraged a great increase of sheep which were kept all year round on the moor. After the 1980s agri-environment schemes were introduced to reduce the sheep numbers to avoid environmental damage. Sheep numbers have reduced and cattle numbers also went down. Nowadays cattle are favoured for grazing schemes because of the issues I mentioned regarding Molinia. Whilst cattle numbers have gone up a bit across Dartmoor there are not enough to munch all the freshly burnt Molinia. The problem is that it is summer grazing by cattle that is required and not all year round grazing so the problem arises as to where the cattle go when they leave the moor in the autumn. I hope that makes it clearer – as with all things Dartmoor it is mighty complicated.

  4. Pingback: The politics of rewilding on Dartmoor – A Dartmoor blog

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