Evidence Over Opinion: A Scientist’s View on Moorland Management

In the often-heated debate over moorland management, objective, long-term scientific evidence can be hard to find. To clarify the complex science behind managing heather moorlands, Scotland’s Regional Moorland Groups and Scottish Gamekeepers Association turned to the work of Dr. Andreas Heinemeyer, an Associate Professor at the University of York.

You can watch the interview with Dr. Heinemeyer and read a summary of the key points below:

With over 15 years of research focused on peatlands, including a decade-long study commissioned by Defra and Natural England, Dr. Heinemeyer provides a crucial, evidence-based perspective. His research moves beyond common headlines to assess the real-world trade-offs of different management strategies.

As Dr. Heinemeyer states, his goal is to cut through the noise and focus on the core issues:

"I think as a scientist what I try to do is look through that to really focus on the actual issue of prescribed burning."

The Real Problem: A Lack of Clear, Long-Term Evidence

Dr. Heinemeyer's primary finding is that the existing scientific evidence on the impacts of heather burning is "surprisingly little known", "very limited", and often contains "very conflicting evidence."

His view is corroborated by others in the scientific community; he notes key papers published in 2016 and 2018 which concluded that the long-term impact of prescribed burning in the UK is simply not known, and even less is known about the alternatives.

A critical flaw he identifies in many studies is their failure to separate the impacts of heather management from the impacts of historical drainage. It is universally agreed that drainage is detrimental to peatlands. However, the effects of management techniques on wet, undrained peat is a separate issue that must be assessed on its own, and many studies have conflated the two, clouding the results.

This highlights the absolute necessity of long-term research. Dr. Heinemeyer notes that the initial five-year period of his own study was not long enough to draw meaningful conclusions. Scientific peer reviewers agreed, recommending the study be extended to an "ideally a 20-25 year-long" duration to truly understand the slow-moving processes and long-term effects on these complex ecosystems.

Comparing the Options: The Trade-Offs of Burning, Cutting, or Doing Nothing

Dr. Heinemeyer's research directly compares three different approaches to heather moorland management: prescribed burning, cutting, or leaving it unmanaged. The findings reveal that each option involves significant trade-offs that shift over time, and there is no simple "good" or "bad" choice.

The Surprising Risks of 'Doing Nothing'

Leaving heather unmanaged might seem like a natural, risk-free option, but the research identifies two significant negative consequences.

• Drying Out the Peat: As heather grows old and tall, its large biomass transpires a great deal of water, drawing moisture directly from the peat below. This causes the peat itself to dry out, which is a major concern. As Dr. Heinemeyer explains, this is a "very big concept concern because locking away carbon in peatlands relies on peat being wet, anything which dries it is bad."

• Tree Invasion: On deep peatlands, where there is little evidence of historical forest cover, unmanaged ground is vulnerable to colonisation by non-native trees like Sitka Spruce. These trees are highly efficient at self-seeding and dry out the peat very effectively. While establishing woodland can be beneficial in the right place, Dr. Heinemeyer cautions that on deep, wet bogs, "trees on a wet bog is a bad idea" because the vast majority of the landscape's carbon is stored in the peat, not the vegetation.

Crucially, this progressive drying of the peat from unmanaged vegetation significantly increases the risk of a catastrophic wildfire, creating a tinderbox landscape.

Cutting vs. Burning: A Question of Timescale and Carbon

The comparison between cutting and burning is not straightforward, as the carbon outcomes change dramatically depending on the timescale of measurement.

• Initial Carbon Loss:

  • Burning: Creates a large, immediate loss of carbon to the atmosphere, which has "gone up in smoke."

  • Cutting: Avoids this initial combustion loss, but the cut heather, or "brush", is left on the ground where its decomposition leads to carbon losses that are "quite large year after year after year."

• Long-Term Carbon Storage:

  • Burning: Incomplete combustion creates stable charcoal (biochar), a material that "doesn't tend to decompose so it's locked away carbon" and forms a key part of the peatland's long-term carbon budget.

  • Cutting: The slow but continuous decomposition of the cuttings means that over a 20-year cycle, the total carbon lost to the atmosphere can become very large.

• The 20-Year Verdict:

  • Dr. Heinemeyer makes a crucial point: a short-term, five-year view is not just incomplete - it is actively misleading. After five years, burning looks like a "huge enormous loss" of carbon. However, viewed over a 20-year cycle, the picture "looks completely different."

  • When the long-term effects are accounted for, specifically the creation of stable charcoal and lower ongoing losses, prescribed burning performed under the right wet conditions "actually might lock away more carbon... than when you cut it."

Water and Wildlife Habitat

The different management techniques also have distinct effects on water levels and habitat structure. Initially, burned plots can be drier due to faster water runoff. However, the research shows a fascinating shift over time: after about five years, the burned plots can actually become wetter than unmanaged plots.

In contrast, cutting with heavy machinery flattens the vital 'micro topography' (the small-scale hummocks and hollows) destroying the varied structure that ground-nesting birds depend on for finding dry nesting sites within a wet bog. Prescribed burning, which does not involve heavy machinery, maintains this essential ground structure.

The Elephant in the Room: Preventing Catastrophic Wildfire

A critical factor in management debates is the increasing risk of wildfire due to climate change. Dr. Heinemeyer makes a vital distinction: prescribed burning is not "peatland burning." It is the controlled burning of surface vegetation, conducted during wet and cold winter months for a specific reason: to ensure that only the surface vegetation burns while the wet peat below remains protected and undamaged.

"It's not peatland burning," he clarifies. "If anything, it actually prevents the peatland from burning. It burns the surface vegetation in a prescribed way to counteract the risk of a catastrophic wildfire."

A wildfire on a dry peatland is a completely different and devastating event. The fire can burn deep into the peat itself, smouldering for weeks or months and resulting in the loss of "decades hundreds of years maybe even thousands of years of accumulated carbon." Prescribed burning is an internationally recognized tool used to reduce the build-up of vegetation (fuel load) and prevent these uncontrollable wildfires.

A Call for Common Sense and Collaboration

Based on his long-term research, Dr. Heinemeyer offers clear recommendations for moving forward on moorland management policy.

1. Look at the Landscape, Not Just the Magnifying Glass: A study focused on a small plot can make a management impact look huge, but the actual effect at the landscape scale may be negligible. Policy must be based on the reality of the entire landscape, not just isolated, magnified plot-level data.

2. Use the Right Tool for the Right Place: There is no "one tool fits all" solution. Land managers need a full toolbox of options, including burning, cutting, re-wetting, and grazing, to apply to different conditions. This flexibility is crucial precisely because the long-term evidence for any single approach is still developing, and managers must be able to adapt to the specific needs of the landscape.

3. Move Beyond Politics and Follow the Evidence: Dr. Heinemeyer calls for an end to the "black versus white" polarisation of the debate. Instead, landowners, government agencies, land users, and scientists must work together to build a shared understanding based on scientific evidence. As he puts it: "we need to have an open debate on this until we have the evidence and I think that's where government agencies and land owners and land users need to work together."

An Evidence-Based Future for our Moorlands

Managing our invaluable moorland landscapes is a complex, long-term responsibility that cannot be guided by simplistic headlines or misleading short-term data. The comprehensive research from Dr. Andreas Heinemeyer demonstrates that the choices involve significant trade-offs that only become clear over decades.

His work shows that traditional management tools like prescribed burning have a valid, scientifically observable place in modern conservation, particularly as our understanding of the long-term evidence continues to develop. These tools are essential for maintaining healthy, resilient landscapes and, crucially, for protecting their vast and vital carbon stores from the growing threat of catastrophic wildfire.

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