A new study mapping moorland burning has been published by RSPB in the peer-reviewed journal Remote Sensing in Ecology and Conservation. https://zslpublications.onlinelibrary.wiley.com/doi/10.1002/rse2.389
RSPB Conservation Scientist Mike Shewring describes the main findings.
Moorland burning in the UK, conducted for Red Grouse shooting, deer and livestock grazing, has come under increasing scrutiny due to evidence of its environmental impacts, especially on peat soils. With the introduction of regulations in England aiming to reduce the environmental impacts of burning, and the recently introduced Muirburn Bill in Scotland, it is important to understand whether practitioners are moving towards more environmentally sustainable burning practices. Our new study maps how much burning takes place annually, where it takes place, and whether it overlaps with sensitive features such as peat soils, protected areas, steep ground and alpine habitats.
Visual mapping of burning is time consuming, so we developed a method to automatically detect and map the appearance of new burn scars in moorland vegetation each year, using high resolution satellite images. Following extensive validation of the methods, we achieved a high level of accuracy, giving us confidence in what the maps were telling us.
The availability of suitable imagery from 2017 onwards meant we could map burning across five consecutive years from 2017/18 to 2021/2022. Total areas burned each year were 8,332 to 20,973 hectares (average yr -1), with average annual areas per country of 5,902 ha (England), 9,047 ha (Scotland), and 325 ha (Wales). Across the five years, most burning was detected in Northern England, South-East Scotland, and the Scottish Highlands (Figs 1 and 2). One notable result was a marked reduction in the area burned in England in 2021/22 - at 1,859 ha it was 73% lower than the average of the four previous years in England. This reduction was not mirrored to the same extent in Scotland or Wales, suggesting it may be related to the regulation introduced in England in May 2021, aiming to limit burning over peat soils within protected areas here.
Fig. 1. Extent of moorland burning across Great Britain in five (2017/18 to 2021/22) burn seasons. Burning is mapped here at 2.5km grid square resolution (6.25km2) as the total number of pixels burned across the five seasons. Inset map shows Dartmoor and Exmoor.
Figure 2 Area of moorland burning in Great Britain across five burn seasons; a) Total predicted burn area by country (blue= England, green = Scotland, yellow= Wales) (95% CI around total predicted area shown as red lines); b) Same data for each country separately to aid interpretation
Approximately a third of moorland burning (average 5,000 ha yr-1) detected in Great Britain occurred over soils defined as deep peat (in other words over 40cm or 50cm depth depending on the definition used in each country), although this was more prevalent in England than Scotland (46% and 27% respectively). Burning over deep peat contravenes existing moorland burning guidance - The Muirburn Code and the Heather and Grass Burning Regulations and Code (England). Interestingly, although the total area burned in England reduced in 2021/22 (see above), the percentage of burning over peat soils only fell to 41% from 49% over the previous four years) suggesting that considerable areas of peat soils are still burned in England.
Understanding burning in the UK’s Special Areas of Conservation (SACs) and Special Protection Areas (SPAs) is important because many of these are deemed to be in poor (‘unfavourable’) condition, with burning identified as a key contributor to this.
The study detected burning in many protected areas, with those in the North of England, and especially the North York Moors SAC/ SPA, subject to the highest percentage area burned. The area burned in protected sites did fall in England and Scotland in 2021/22 compared to the four previous years by approximately two thirds in English PA’s and one third in Scottish PAs. This may have been due to the introduction of new legislation (2021) in England.
Existing guidance also advises against moorland burning in sensitive areas, including slopes steeper than 27°, or 18° over blanket mire or wet heath, due to the risk of increased erosion, loss of soil carbon and impacts on water quality.
The study detected 1,173 ha of burning on steep slopes (1.6% of total burn extent) over the five years and this showed no obvious trend over the five years. This burning occurred mainly in the Cairngorms, but also in the North York Moors, Lammermuir Hills and Northwest Highlands.
Alpine habitats in the UK generally occur above approximately 600m elevation but can be found at lower elevations further north and west. Understanding the extents of burning in alpine habitats and any changes in this through time is important because these habitats are particularly sensitive to disturbance and are already under pressure due to climate change.
A total of 158 ha of burning (0.2% of GB total) occurred in alpine habitats over the five years and this varied little between years (26 – 37 ha, mean of 32 ha). Alpine burning occurred mainly in the Cairngorms and Northwest Highlands of Scotland,
Moorland burning in the UK uplands is widespread and extensive in area. Where found it often does not comply with guidance to avoid deep peat soils and steep slopes. A recent reduction in burned area in England does, however, suggest that new regulation to reduce burning over peat soils has been somewhat successful. It also highlights little evidence of voluntary reductions in burning prior to the introduction of regulations in England. This further suggests that the Wildlife Management and Muirburn Bill Scotland is required.
However, there is also a need to confirm that regulation continues to be effective in future and our methods allow this in order to track changes in the location, extent and frequency of burning and correspondingly the effectiveness of regulation.