Does burning the heather do more harm than good?

Muirburn involves the controlled burning of old heather and grass to promote new growth.

It is a tool used traditionally by a wide range of land managers in Scotland, including gamekeepers, hill farmers and crofters.

It is primarily used to improve grazing for livestock or provide food and shelter for red grouse, but it is also perceived to reduce wildfire risk.

The Muirburn Code sets out statutory restrictions and good practice for land managers who burn moorland vegetation.

Currently muirburn can take place between October 1 and April 15 (or April 30 with the permission of the landowner) without a licence.

However, the benefits and disadvantages of muirburn are contested.

In particular, there are concerns about the continuation of muirburn, especially on peatlands, at a time when we are trying to address the ongoing climate and biodiversity emergencies.

My team at the farms, together with colleagues from SRUC Edinburgh, recently completed a review for NatureScot of the available evidence on the impacts of muirburn on wildfire prevention, biodiversity conservation and carbon sequestration.

The research published to date has focused on a limited number of sites across the UK and has mostly taken place on blanket bog.

The latter is not representative of all moorlands on which muirburn may be conducted. This, and the overall lack of studies available, limited the conclusions we could draw.

The known impacts on biodiversity are mostly clear-cut but are nevertheless mixed.

There are winners and losers, but how these are viewed depends on a land manager’s objectives and the biodiversity under consideration at a site.

Wading birds such as curlew and lapwing are often said to benefit on managed grouse moors, but it is difficult to disentangle the benefits specifically arising from muirburn from the additional benefits that predator control provides. There have been very few studies considering full carbon budgets on muirburn sites. The vast majority of these have focused on the impact of burning on what is called dissolved organic carbon.

This refers to a complex mixture of compounds that represent a key component of the carbon cycle from land into freshwater and marine systems. While it is important to understand these processes, these studies did not consider what impact muirburn may be having on the carbon stored in the soils.

Finally we found that there have been no real direct studies on the association between muirburn and wildfires.

Any previous conclusions have been drawn indirectly from the fact that reducing vegetation biomass – or fuel load – on a moorland through muirburn might be expected to reduce the risk of any subsequent wildfire.

This has, however, not been studied specifically for muirburn.

Conversely, there is some evidence to suggest that a proportion of muirburn leads to wildfires. The exact proportion is unknown, nor what type of muirburn may have a higher likelihood of developing into such wildfires.

Our review was commissioned by NatureScot because an independent group set up by the Scottish Government, the Grouse Moor Management Review Group, produced a report in 2019 that made a number of recommendations, including introducing legislation to require a year-round muirburn licence.

NatureScot will now form a small sub-group of their Scientific Advisory Committee to provide them with advice on how to take a risk-based approach to muirburn licencing in the face of an unclear evidence base. It is, however, essential that hill farmers and crofters are aware that the 2019 report made clear that the licensing regime will apply to all muirburn and not just that carried out on grouse moors.

BURNING QUESTION: Muirburn has been practiced for centuries but do the benefits in land management outweigh its harm to the environment?