Burning terms – seeing the smoke for the trees!

By Henrietta Appleton, GWCT Policy Officer (England)

You would think that there would be a single term to describe the removal of surface vegetation such as scrub, heather and grasses using fire. But this is not the case. There are regional terms, legislative terms and then just plainly incorrect terms resulting in nine possible descriptors for a single practice.

So let us try and lift the mystery on what each term means in practical terms, its accuracy as a descriptor and its relevance to the political debate over this form of land management. In this we have been greatly aided by an expert report on wildfire by Belcher et al (2021) for the Climate Change Committee’s third Climate Change Risk Assessment.

Peatland or Peat Burning: the first and most important point to make is that this term is factually incorrect, and its use is either disingenuous or a result of misplaced understanding. We have recently raised our concerns about its inappropriate use with organisations such as Greenpeace and Wildlife & Countryside Link. The use of fire to manage surface biomass (vegetation) has been a long-standing cultural activity both in the UK and globally such that many ecosystems have become fire-adapted, UK peatland being one.

But in every case the aim is not to burn down into the peat, but merely to use fire to skim the surface and remove the vegetation to instigate re-growth, re-invigorate habitats and to protect the peat. In the face of our changing climate this helps prevent intense wildfires which do destroy the peat (it has been estimated that the average depth of peat loss in the Saddleworth Moor wildfire in 2018, which affected over 18 km2 (c1800 hectares) of moorland, was 6cm(1) - 200 years’ worth of sequestration).

The remaining terms are all factually correct and reflect a practice that is subject to Heather and Grass, etc (Burning) Regulations and a voluntary code of practice – the Heather & Grass Burning Code in England & Wales and the Muirburn Code in Scotland.

This means that burning is only permitted to take place under certain weather conditions between October and mid-April (when conditions are cooler and damper), over small areas (the Heather and Grass Burning code suggests a maximum of 30m by 600m (or c1.8 hectares)) with cut margins as fire breaks surrounding them, and a fire-fighting team of gamekeepers in attendance with fire fogging units and leaf blowers to extinguish flames quickly. The 2021 regulations prohibit burning on peat more than 40cm deep except under licence.

‘Cool’ Burns: This term is often employed when describing the nature of the fire used in vegetation management. It is a layman’s term that essentially describes a low temperature fire that merely removes the surface vegetation. As a result, ‘cool’ burns have a short-term effect on the ecosystem on which they are used – grasslands, heathlands or peatlands. The opposite are ‘hot’ burns or wildfires with high to extreme destructive fire intensity. It sounds like an oxymoron, but ‘cool’ burns really are cool – watch this amazing video to see why:

Rotational Burning: this term has been widely used to describe the use of fire to manage vegetation on moorland landscapes subject to grouse moor management. As Belcher et al (2021) says “It describes the planned burning of small areas of older heather in rotation over the years. The fires should be low intensity, quick, cool burns that remove the heather canopy but do not impact the underlying soil or peat.”

Whilst this term is therefore technically correct it has resulted in the practice being seen as conforming to fixed rotations of say 10 or 15 years when in reality this is not the case as different areas of a moor will have different growth rates (due to underlying soil type, vegetation type, aspect, altitude etc).

Consequently, those involved in upland management have sought to move towards adopting more progressive terms that better describe burning based not only on vegetation growth rates but also desired outcomes. Incidentally this term was used in the press release accompanying the regulation that banned burning on deep peats(2).

Controlled Burning: One of the preferred progressive terms; it emphasises that fire is being used in a controlled manner to deliver desired outcomes rather than defined rotations and therefore moves towards a more prescriptive approach.

Controlled burning employs the same “low intensity, quick, cool burns that remove the heather canopy but do not impact the underlying soil or peat” with, on grouse moors at least, the same objective of using fire to improve habitat diversity for red grouse but also to promote biodiversity, create habitat for specific species, or remove heavy fuel loads to lower wildfire risk as evidenced in the GWCT’s recent audit of grouse moor management – Sustaining ecosystems: English Grouse Moors(3).

Controlled burning is also used to describe burning practices on grasslands, heathlands and forestry. For example, the Forestry Commission splits controlled burning into three stages:

1. setting the objectives/ prescription for the burn
2. planning and liaison
3. burning under control and extinguishing fire(4)

Prescribed Burning: The term most often used by scientists; it emphasises that the activity is related to a specific outcome. Belcher et al defined it as “The use of fire to remove heavy fuel loads to lower wildfire risk and/or improve land for a variety of reasons including for biodiversity or creating habitat for chosen species. This approach differs from controlled burns as true prescriptions will develop use of specific fire behaviour, toward generating a chosen impact. This approach builds on controlled burns and true prescriptions of the use of fire on landscapes are in their infancy in the UK, as more research is required to develop fire usage that has well specified effects.”

As heather burning practices evolve to meet both sporting and environmental outcomes (such as carbon management, biodiversity and wildfire prevention) the term prescribed burning becomes more appropriate. Research is demonstrating that the cool burns undertaken on grouse moors are an effective use of specific fire behaviour to protect carbon stores in peatland and in aiding Sphagnum moss recovery(6).

Managed Burning: There appears to be no distinct definition of this term as it is used inter-changeably with prescribed, rotational and controlled burning. In many ways it is an umbrella term for these burning approaches as it emphasises that the fires have been deliberately lit for land management purposes(7) e.g. sheep grazing, game shooting or conservation.

Tactical burning: This term specifically relates to activities undertaken by the Fire & Rescue Service usually in the use of fire to remove fuel ahead of the fire front (i.e. to create fire breaks) in a wildfire to prevent its spread and avoid major incidents. At least five Fire & Rescue Service areas use this as a key tool for both the prevention and intervention of wildfires(8).

There are also regional terms for the use of fire in vegetation management.

Muirburn: is the term used in Scotland for “the intentional and controlled burning of moorland vegetation”(9). However, the supplementary guide to the Muirburn Code gives it a more detailed definition akin to that of prescribed burning in that its practice relates to a specified time of day and season, weather conditions and fuel conditions in order to meet one or more of four planned land management objectives, namely: improving vegetation digestibility, maintaining moorland vegetation diversity, maintaining internationally renowned moorland landscapes and reducing risk of wildfire.

Swaling: is a local, cultural (in that it has been used for hundreds of years) term used in the South and South West to reflect the use of burns to encourage regeneration of vegetation for livestock grazing and the maintenance of open, wild moorland landscapes e.g. Dartmoor. Like the other forms of controlled burning it is subject to the Heather and Grass, etc (Burning) Regulations and a code of practice.

There are five conclusions from this review of burning terms:

1. All emphasise that the fires are under the control of man.
2. All are subject to regulation and a voluntary code that ensures they are undertaken in conditions and in a manner that limits the risk of the fire getting out of control.
3. The objective in each situation is to remove the surface vegetation only. In this respect low temperature fires or cool burns are key.
4. Each term, bar one, is essentially correct although the use of the term rotational burning is considered less appropriate given its implication of burning by rote not outcome.
5. There is no such term as peatland or peat burning.

What is also clear is that as ecosystem service demands on our habitats have changed from just provisioning (i.e. livestock production) to regulating (i.e. wildfire prevention and carbon management) and cultural (i.e. recreation) so management approaches need to change.

Consequently, the use of ‘cool’ burning in support of red grouse populations and sheep grazing has evolved to deliver a more ecosystem services approach and therefore the more prescriptive use of controlled fires. Grouse moor managers appreciate this distinction and should be rewarded as they evolve their controlled burning practices in pursuit of emerging public policy demands.

[1] Belcher et al., (2021) UK wildfires and their climate challenges. Expert Led Report Prepared for the third Climate Change Risk Assessment
[2] https://www.gov.uk/government/news/englands-national-rainforests-to-be-protected-by-new-rules
[3] https://www.gwct.org.uk/englishgrousemoors/
[4] Belcher et al., (2021) UK wildfires and their climate challenges. Expert Led Report Prepared for the third Climate Change Risk Assessment
[5] Flanagan, NE, Wang, H, Winton, S, Richardson, CJ. Low‐severity fire as a mechanism of organic matter protection in global peatlands: Thermal alteration slows decomposition. Glob Change Biol. 2020; 00: 1-17.
[6] Whitehead, S., Weald, H., Baines, D., Post-burning responses by vegetation on blanket bog peatland sites on a Scottish grouse moor. Ecological Indicators, Volume 123, 2021, ISSN 1470-160X.
[7] Worrall, Fred, et al. (2010) "Impacts of burning management on peatlands." Scientific review. IUCN Peatland Programme.
[8] Belcher et al.
[9] Holland, J.P., Pollock, M., Buckingham, S., Glendinning, J. & McCracken, D. 2022. Reviewing, assessing and critiquing the evidence base on the the impacts of muirburn on wildfire prevention, carbon storage and biodiversity. NatureScot Research Report 1302