How Natural England’s Review Fails to Reflect the Science on Heather Burning

Controlled heather burning on peatlands is a contentious topic central to the management of UK uplands. At the heart of the current policy debate are two key scientific reports that offer strikingly different interpretations of the available evidence.

The first is a comprehensive review from the University of York, "Prescribed heather burning on peatlands: A review of ten key claims made about heather management impacts and implications for future UK policy" (hereafter the 'York review'). It critically examines the evidence base to facilitate an informed and unbiased debate.

The second is Natural England's "An evidence review update on the effects of managed burning on upland peatland biodiversity, carbon and water" (NEER155), which updates its previous findings and informs government policy.

This post examines 10 key claims about heather burning, comparing the findings of the York review directly against NEER155's conclusions. This analysis reveals how NEER155 appears to systematically misrepresent the scientific evidence through four common methods:

• Overloading with complexity: burying key findings in dense detail

• One-sided caveats: applying scrutiny to evidence that contradicts a preferred narrative but not to supporting evidence

• Selective weighting: giving undue prominence to minor findings

• Framing by omission: ignoring crucial context that would alter the conclusion

For sound policy to be developed, it must be built on a fair and balanced assessment of the best available science. This comparison aims to clarify what that science actually says.

Claim 1: Burning Causes Long-Term Carbon Loss

The York Review: Acknowledging Deep Uncertainty

The York review concludes there is a "paucity of empirical evidence" to prove that prescribed burning has either a net positive or negative effect on long-term carbon storage. It explains that existing carbon studies provide "contradictory evidence" because they fail to assess the entire management cycle, which is approximately 20 years, or all elements of the carbon budget.

The review also highlights often-overlooked factors, such as the potential benefits of charcoal production (which may suppress methane emissions) and the important carbon input from heather roots.

NEER155's Conclusion: A Definitive Negative Impact

NEER155 concludes that burning can switch peatlands from a carbon sink to a source (Conclusion 13.42). It summarises that "burning increased net GHG emissions and that burned and cut plots were GHG sources compared to longer unburned comparisons which were GHG sinks" (Table 30, citing Heinemeyer et al., 2019c).

Spotting the Flaws

• Framing by Omission: NEER155’s summary conclusion presents a definitively negative outcome for carbon, omitting the "paucity of evidence" and significant scientific uncertainty that is strongly emphasised by the York review.

• One-sided Caveats: While NEER155 acknowledges "inconsistent evidence" on Dissolved Organic Carbon (DOC) at the plot scale within the body of its report (Table 30), its main conclusions (13.42, 13.50) present an overwhelmingly negative picture of burning's impact on carbon, downplaying studies that show no significant effect.

By presenting a definitive conclusion where none scientifically exists, NEER155 replaces the crucial need for more research with a misleading sense of certainty.

Claim 2: Fire and Heather Dominance are Recent Phenomena

The York Review: A Millennium of Cyclical Change

Using palaeoecological records from peat cores, the York review shows that fire and heather dominance are not recent phenomena. It provides evidence of frequent local fires occurring well before the intensification of grouse moor management.

The review states that vegetation cover has often been "cyclical during the past millennium" and that the key drivers of these historical changes - whether climate, grazing, pollution, or burning - remain "largely unknown."

NEER155's Conclusion: A Modern Management Problem

NEER155's palaeoecological section notes that the 20th century saw a rise in charcoal linked to a "major change of vegetation community" towards grass or heather (Calluna) dominance. It concludes there is "moderate evidence" that "fire and grazing... resulted in a switch to graminoid - or Calluna-dominated vegetation" (Table 28).

Spotting the Flaws

• Framing by Omission: NEER155 focuses on changes since the industrial revolution. This omits the crucial context from the York review that fire and heather dominance have been cyclical features of these landscapes for over a thousand years, thereby framing them as a modern problem linked exclusively to current management practices.

This omission misrepresents the ecological history of our uplands, portraying a natural cycle as an unprecedented, modern crisis.

Claim 3: Burning Reduces Sphagnum Moss

The York Review: Evidence of Post-Burn Increase

The York review provides evidence that contradicts this claim, citing multiple studies (e.g., Whitehead et al. 2021, Heinemeyer et al. 2023) where Sphagnum moss cover actually increased after burning. It explains that prescribed fire can open up old, dense heather canopies that would otherwise suppress Sphagnum growth.

The review also challenges the idea that Sphagnum is the sole significant peat-forming vegetation, pointing to contradictory statements on this matter from the IUCN itself.

NEER155's Conclusion: Highlighting a Single Negative Finding

NEER155 concludes there is "moderate evidence that Sphagnum... show a range of responses to burning," including initial declines, little change, or some recovery (Conclusion 13.14).

However, it specifically highlights that a re-analysis of data from the Hard Hill experiment suggests that large burns in 1954 had a negative effect on Sphagnum that was "still apparent" over 60 years later.

Spotting the Flaws

• Overloading with Complexity: While NEER155 acknowledges mixed results for Sphagnum deep within its report (para 4.49-4.50), its main conclusion elevates a single, historical negative finding from the Hard Hill site. This buries the more recent positive or neutral findings from other studies cited in the York review. This creates the misleading impression that the evidence is predominantly negative, when in fact recent, robust studies show positive or neutral outcomes that are more relevant to modern prescribed burning practices.

• One-sided Caveats: NEER155's own text dedicates significant space (para 4.9) to the experimental limitations of the Hard Hill site, noting issues like its "meso-scale structural features," problematic pre-experiment burning history, and "trampling effects from surveyors." Yet, it elevates a negative interpretation from this very same site in its main conclusion without applying similar critical caveats.

This selective elevation of a flawed, historical data point over more recent, relevant science presents a distorted picture of burning's impact on this key peat-forming moss.

Claim 4: Prescribed Burning Increases Wildfire Risk

The York Review: Burning as a Wildfire Mitigation Tool

The review presents evidence that unmanaged, ageing heather dries out the surface peat over time. This, combined with a much higher fuel load, "poses a greater risk of more frequent and damaging... fires."

In this context, prescribed burning is a critical management tool used to reduce high fuel loads and mitigate the risk of severe wildfires that are hot enough to ignite the peat soil itself.

NEER155's Conclusion: Burning as a Cause of Wildfire

NEER155 finds only "weak evidence of any direct effect of managing biomass by burning... on wildfire ignition, behaviour, severity or extent in the UK" (Conclusion 13.70). In contrast, it concludes there is "strong evidence that managed burns escaping control cause a proportion of wildfires, particularly in the uplands" (Table 34).

Spotting the Flaws

• Framing by Omission: NEER155 focuses on 'escaped burns' as a cause of wildfire while completely omitting the core argument presented in the York review: that prescribed burning is a critical tool for reducing fuel loads to mitigate the severity of future, inevitable wildfires. This frames burning as a source of the problem, not a key part of the solution.

By focusing only on escaped burns and ignoring the role of prescribed burning in fuel load reduction, NEER155 frames a key mitigation tool as a primary cause of the problem, a misrepresentation with serious implications for wildfire resilience strategy.

Claim 5: Rewetting Peatlands is a Standalone Solution for Wildfire

The York Review: A Promising but Untested Approach with Limits

The York review states that while rewetting should generally reduce fire risk, this approach has "limitations and has never been tested within UK upland peatlands." It raises the concern that even rewetted peatlands can dry out during extreme summer conditions, and high vegetation fuel loads will still pose a significant combustion risk. The review notes that rewetting does not make peatlands "generically ‘fireproof’."

NEER155's Conclusion: A Proven Primary Solution

NEER155 concludes there is "strong evidence that the severity and perhaps incidence of wildfires may be reduced when wetter conditions, in particular a high water table, are maintained or restored" (Conclusion 13.69). It recommends restoration, including rewetting, "to reduce risk of, and increase resilience to, wildfire" (Table 34).

Spotting the Flaws

• One-sided Caveats: NEER155 presents rewetting as a primary solution for wildfire mitigation but fails to include the significant caveats raised in the York review about its practical limitations and the lack of UK-specific testing. It highlights the benefits of rewetting without acknowledging its uncertainties.

This uncritical promotion of rewetting as a panacea, while ignoring fuel load management, risks creating a false sense of security and could lead to policy that is ill-equipped to handle future wildfire threats.

Claim 6: 75% of the World's Heather Moorland is in the UK

The York Review: Questioning a Widely Used Statistic

The York review states this is an "unsubstantiated claim" based on uncertain and outdated data that failed to account for heather moorland in many other countries. The review cautions against using such percentages due to poor definitions and a lack of robust calculations, even while acknowledging that UK heather moorland is "substantive and globally important."

NEER155's Conclusion: No Engagement with the Claim

NEER155 does not engage with or evaluate this widely circulated claim in its evidence review.

Claim 7: Burning Harms Water Quality and Colour

The York Review: A Lack of Clear Evidence and Confounding Factors

The review found a "lack of clear evidence on direct impacts" and noted that associating impacts with burning is difficult due to many "confounding aspects" like historic drainage and atmospheric pollution.

It highlights the contradictory evidence between laboratory studies (which can indicate increased water colour) and field studies where this effect does not translate. Furthermore, robust reviews (e.g., Harper et al. 2018) suggest that "drainage is likely to be the major cause of increased DOC concentration."

NEER155's Conclusion: Upholding an Old Narrative Despite New Evidence

NEER155 found "inconsistent evidence that burning effects DOC and water colour at the plot scale" (Table 30). However, its updated conclusion for watercourses is that while recent studies are inconsistent with previous findings of an increase, there is still "strong evidence that burning leads to increased DOC/water colouration in watercourses" (Table 30).

Its overall conclusion is that burning is associated with "changes to various aspects of water chemistry... and peat physical properties" (Conclusion 13.50).

Spotting the Flaws

• One-sided Caveats: Here, NEER155's updated conclusion is in direct conflict with its own summary of the most recent, robust evidence. Its analysis (Table 30) explicitly states that new BACI studies like Heinemeyer et al. (2019c) are "not consistent with NEER004 finding" that burning increases DOC in watercourses. Despite this new, stronger evidence showing no effect, the "Updated conclusion" maintains the old negative narrative, a clear case of prioritizing a pre-existing conclusion over new scientific findings.

This decision to ignore its own updated evidence demonstrates a concerning commitment to a particular narrative, regardless of what the latest science indicates.

Claim 8: Burning Negatively Impacts Water Flow and Increases Flood Risk

The York Review: Highly Site-Dependent Impacts

The review states that the only robust catchment-scale BACI (Before-After-Control-Impact) assessment (Heinemeyer et al. 2023) shows that the impacts on water flow are "highly site dependent."

This study found reduced flow from cut versus burnt catchments at two of three sites, but this was not compared to unmanaged catchments. Crucially, it also found that heather cutting "greatly affected" microtopography, which is vital for hydrology.

NEER155's Conclusion: A Focus on Negative Comparisons

NEER155 concludes that "stream flow is affected by burning and vegetation composition" and cites the Heinemeyer et al. (2019c/2023) finding that "streamflow response to rainfall was faster and greater on burnt compared to cut sub-catchments" (para 7.35). Its summary table concludes there is "evidence of more frequent runoff after burning" (Table 31).

Spotting the Flaws

• Framing by Omission: By focusing on the comparison between burning and cutting, NEER155 omits the crucial context from the York review that the effects are "highly site dependent." Crucially, it presents this comparison without noting that an unmanaged control was absent, making it impossible to conclude that burning is worse than doing nothing. It also fails to mention that cutting has its own significant negative impacts on microtopography, a critical factor for landscape hydrology.

This selective reporting creates an incomplete and biased comparison, potentially leading policymakers to favour alternatives without understanding their full environmental cost.

Claim 9: Peatlands offer huge carbon sequestration potential and are climate change ‘saviours’

The York Review: A Nuanced View on Potential and Risks

The review rejects the simplistic idea of peatlands as unconditional 'climate saviours'. It accepts they are a vast, globally important long-term carbon store, but stresses that historic storage is not the same as future sequestration potential.

This potential depends on condition and history: restoring degraded sites can deliver major gains, while intact sites offer little extra benefit. The review also notes that peatlands emit methane (CH₄), especially when very wet or rewetted, and that climate change and wildfire make future carbon gains highly uncertain.

It concludes that protecting existing stocks is more important than overselling peatlands as a simple climate solution.

NEER155's Conclusion: Emphasising Carbon Storage and Ecosystem Services

NEER155 stresses peatlands’ carbon storage role and their degraded condition across much of the UK. It says managed burning releases carbon through combustion before gradual recovery, with mixed evidence on long-term balance, but suggests burning can turn peatlands from sink to source.

Spotting the Flaws

• Framing by Omission: NEER155 ignores York’s key caveat, that historic storage is not the same as future sequestration, and omits the methane trade-off from rewetted peat.

• One-sided Caveats: NEER155 highlights carbon storage as a primary service but downplays limits and risks, including climate change and wildfire threats.

This approach fails to provide policymakers with a complete picture, potentially creating a false sense of security about the role of peatlands in climate mitigation while downplaying the urgent need to protect their existing carbon stocks from future threats.

Claim 10: Burning Has Significant Adverse Impacts on Biodiversity

The York Review: Contextualising the "Winners and Losers"

The review finds "very little evidence to support claims of 'significant adverse impacts'". It explains that any management choice results in "winners and losers" and that biodiversity impacts must be contextualised against the conservation status of different species, including ground-nesting birds of high conservation concern like the curlew.

It notes that carefully planned burning can create a mosaic of different vegetation ages that can promote positive biodiversity outcomes.

NEER155's Conclusion: Mixed Effects Without Conservation Weighting

NEER155 finds "strong evidence of mixed effects," noting that wading birds and red grouse tend to be associated with grouse moors (Conclusion 13.26). It adds that predator control has a stronger positive association with some bird densities than burning (Conclusion 13.29). For invertebrates, it concludes burning results in changes to diversity and abundance (Conclusion 13.34).

Spotting the Flaws

• Selective Weighting: NEER155's summary gives equal or greater weight to generalised changes in invertebrate communities as it does to population trends for high-conservation-concern bird species (like curlew and golden plover), which evidence shows can benefit from the habitat management on grouse moors. This creates a false equivalence, potentially leading policymakers to overlook significant benefits for nationally threatened bird species by focusing on generalized, less critical changes in more common invertebrate groups.

By treating all ecological change as equal, NEER155 obscures the specific, and often positive, impacts of management on species of the highest conservation priority.

The Need for Unbiased Science in Policymaking

A side-by-side comparison of the York review and NEER155 on 10 key claims reveals a pattern of systematic misrepresentation in the Natural England report. The cumulative effect of the four identified flaws - Overloading with Complexity, One-sided Caveats, Selective Weighting, and Framing by Omission -  is to present a misleadingly negative and definitive picture of prescribed burning, stripping out the scientific uncertainty and context that is essential for good decision-making.

The danger of NEER155 is not in any single omission or caveat, but in the cumulative effect of these choices. Together, they construct a seemingly robust but fundamentally biased evidence base that consistently downplays scientific uncertainty and omits countervailing findings.

This pattern transforms a complex ecological issue into a simple, negative narrative, a narrative that is easy to translate into restrictive policy but poorly reflects the reality on the ground. This approach contrasts sharply with the York review's consistent call for more robust, long-term, multi-site experimental research (like the BACI approach) to address the genuine scientific questions that remain.

Effective environmental policy for our uplands cannot be based on selective or biased interpretations of science. If a flawed evidence review like NEER155 is left unchallenged, it risks cementing a distorted view of the science. This could lead to poor policy decisions that undermine practical conservation efforts and harm the very ecosystems the policy is meant to protect.

📧 Keep updated on this and all moorland issues - sign up for our FREE weekly newsletter.