Key points
- Lowland heathlands are internationally important habitats that support a wide range of notable and specialist species. These habitats require management to maintain them in good condition.
- Prescribed burning of heathland habitats has quickly become a ‘hot topic’, with growing concerns about the impact of burning and whether cutting can be done instead.
- Most of the research into cutting and burning has been done in upland areas, meaning there is a large knowledge gap surrounding the impacts of different methods on lowland heathlands.
- Scientists set out to study the effects of cutting and burning on lowland heathland in the New Forest National Park, investigating changes in invertebrates and plant communities over time.
- The study found that while cutting can be beneficial, it cannot be a substitute for burning. Prescribed burning remains the most effective way to maintain good quality lowland heathland.
- Any proposed policy changes relating to heathland management must consider the short and long-term conservation impacts on these habitats and the species they support.
Background
Lowland heathlands are important habitats for many species and are found on acidic soils that have low levels of nutrients, usually dominated by shrub species like heather. Since the 1930s, the amount of lowland heathland has declined. However, the UK is home to around 11% of the world’s lowland heathlands.
These habitats are carefully managed to keep them in good condition and prevent them from developing into grasslands or woodlands. Historically, prescribed burning was a frequent management method for lowland heathlands. The process involves planned and controlled burning of vegetation to achieve a specific outcome – for example, to maintain open areas, encourage new vegetation growth, or reduce the risk of wildfires.
In recent years prescribed burning has become more controversial, with growing concerns about the impact of fires on water quality, carbon emissions, habitat condition, and species like amphibians and reptiles. Lots of the debate is linked to the use of prescribed burning on upland heathlands managed for red grouse, which usually involves burning heather in an eight-year cycle to provide young shoots for the birds to feed on. In contrast, prescribed burns on lowland heathlands aim to reduce scrub, usually done on a 20-year cycle.
Lots of research has looked at the impact of prescribed burning in the UK, but around 77% of these studies are from upland areas. This study aimed to address the knowledge gap and help inform both policy and management practices for prescribed burning in lowland areas.
What they did
| What is Common Standards Monitoring? |
| A framework for assessing the condition of a habitat, good or bad. Many habitats – such as woodlands, wetlands, and heathlands – have CSM guidelines which outline specific habitat features and qualities. These guidelines give scientists and other professionals a simple and measurable way to determine if habitats are in good or bad condition. For lowland heathlands, indicators of good quality include 1-10% cover of bare ground and 50-75% cover of dwarf shrubs like heather. Signals of poor quality lowland heathland include more than 10% cover of bracken, or species like ragwort, nettle, and thistles being present. |
The study took place in the New Forest National Park – the largest area of lowland heathland in Europe – where prescribed burns are done on a roughly 23-year cycle across 400 hectares of habitat. The scientists compared the impacts of burning and cutting, and how these effects varied in the 20 years following management being completed.
To assess the impacts of different management methods, the team studied 105 sites with plots that had been managed 0, 1, 6, 10, and 20 years prior, looking at:
- The condition of the heathland, using Common Standards Monitoring
- The different plant species present
- The range of soil, ground-dwelling, and flying invertebrates present
- The amount of food available for birds such as the Dartford warbler and nightjar
What they found
The scientists found no evidence that prescribed burning negatively impacted the heathland condition, plant communities, or invertebrate communities investigated in this study.
Overall, areas of heathland that were managed with prescribed burns were in better condition than areas that were cut. Burned areas exceeded the CSM thresholds for cover of beneficial heather and bare ground, and maintained bracken cover well below the 10% threshold. The condition of burned heathland also continued to improve in the 20 years following the controlled fire. This suggests that removing burning as a management tool is likely to reduce the condition of lowland heathlands.
In contrast, the condition of heathland that was cut had begun to decline within 20 years of it being managed. In this study, cutting was not able to replicate the benefits of prescribed burning, instead creating grassland-like conditions and failing to keep bracken cover below the 10% CSM threshold. Although these conditions resulted in the highest number of plant species being present, they made the habitat unsuitable for many heathland-specialist species over time.
The grassland conditions created by cutting supported more invertebrate species, in higher numbers, providing food for birds like Dartford warblers and nightjars. Generally, invertebrates that were more common on burned or cut sites tended to be species commonly found on heathlands or grasslands.
What does this mean?
Prescribed burns support good quality lowland heathlands, with high cover of beneficial plant species and low cover of less desirable species such as bracken, where cutting was not able to achieve this. This study found no evidence that burning is detrimental to the factors investigated and suggests that burning done on an appropriate cycle results in good habitat condition. In this case, burning on a 20-year cycle maintained good quality lowland heathland habitat.
The results of this study demonstrate that managing lowland heathland with cutting or burning creates different results, and over time, different habitats. Cutting cannot be used as a substitute for burning as it creates grassland-like conditions, however, this can be useful for grazing, providing food for species such as Dartford warblers and nightjars, and creating habitat for invertebrates that prefer grasslands.
These birds are a great example of the different habitat needs many species have. While cutting resulted in there being more insect prey available for the birds, both species nest in heathland habitats – with nightjars using open ground and Dartford warblers nesting in tall heather and gorse. Despite cutting providing them with more food, burning creates nesting habitat for the birds, highlighting the need for both management methods to be available for land managers to use.
In the New Forest around 10% of the heathland is currently cut, and while some cutting is beneficial, this study suggests that increasing the amount of cutting could be negative for biodiversity. Maintaining a mosaic of heathland managed with cutting and burning will likely have the biggest overall benefit for biodiversity, keeping the habitat in good condition and creating suitable areas for a wider range of species.
While there are valid criticisms of prescribed burning, this study reminds us that burning remains the most effective way to manage and maintain good quality lowland heathland habitats. The conservation impact of any policy changes should be strongly considered, keeping in mind the short and long-term effects on the habitats and the species they support.
Read the original paper
Smith, B. M., Carpenter, D., Holland, J., Andruszko, F., Gathorne-Hardy, A., and Eggleton, P. (2023). Resolving a heated debate: The utility of prescribed burning as a management tool for biodiversity on lowland heath. Journal of Applied Ecology, 60(9), 2040-2051.