Claim That “Cessation of Burning Leads to Wetter Peat” Rejected by Scientists

A major scientific review critically examines ten common claims regarding the effects of prescribed heather burning on peatlands in the UK, with "Cessation of heather burning results in wetter peat, less heather cover and no need to burn" being the fifth claim reviewed.

The authors, including Dr. Andreas Heinemeyer, consider the claim unsubstantiated, too generic, and not supported by direct evidence. This claim is part of a broader review of ten common assertions about prescribed heather burning on UK peatlands, and its assessment shares common themes with other critiqued claims, such as the need for better evidence and a more nuanced, site-specific approach to management.

Assessment of Claim

The review argues that Claim 5 draws upon the same unsupported evidence base as Claim 4 ("Rewetting reduces heather dominance and thus protects peatlands against wildfire").

Both claims are rooted in a narrative that a restored, "healthy" peatland requires minimal management and that simply stopping prescribed burning will lead to desirable outcomes. The key arguments against this claim are:

• Lack of Supporting Evidence: There is no direct, applicable evidence to support the idea that stopping burning on its own will lead to wetter conditions and reduced heather dominance. Claims often rely on opinion or on studies that are not relevant to the specific context of UK heather-dominated upland peatlands. For example, studies on the restoration of industrially mined bare peat are not applicable to managing existing vegetated moorlands.

• Contradictory Field Observations: Contrary to the claim, long-term research indicates that unmanaged, ageing heather can actually cause the surface peat to dry out over time. Additionally, field studies have shown that mature heather can be very tall and maintain high cover even on the wettest blanket bog sites, challenging the assumption that wetter conditions inherently reduce heather cover. Heather is physiologically adapted to a wide range of water table depths, including wet conditions.

• Site-Specific Nature of Peatlands: The claim is criticized for being too generic. It fails to account for the unique history, climate, and topography of individual peatland sites, which determine their potential for wetness and long-term ecological trajectories. It is important to recognize that not every site can become as wet as an "ideal" site elsewhere.

Connection to the Broader Context of the Ten Claims

The critique of Claim 5 fits into the larger context of the evidence review, which identifies several overarching issues with common assertions about prescribed burning. The analysis of Claim 5 highlights these broader themes:

1. Challenging the 'Precautionary' Approach: The call to stop burning is often framed as an ill-defined "precautionary" policy approach. The authors argue that such a policy is not based on solid evidence and should not be used when the consequences of alternative management strategies (or no management) are even less understood.

2. The Need for Better Methodology: The review repeatedly calls for robust, long-term studies to assess management impacts. For Claim 5, it recommends a Before-After-Control-Impact (BACI) approach, along with measurements and models, to test different long-term scenarios under various conditions. This would allow for a more reliable comparison of management methods.

3. Recognizing Management Trade-Offs: The review argues against the perception that prescribed burning is the only management practice with negative effects. Alternative approaches like cutting are less studied and are not necessarily a "safe" or "only positive" solution. Furthermore, unmanaged heather can increase fuel loads, posing a greater wildfire risk, especially with climate change projections of hotter, drier summers.

4. Flawed Generalizations: A central theme of the entire review is the danger of making sweeping generalizations about complex ecosystems. Like many of the other nine claims, Claim 5 is rejected because it is site- and time-dependent and fails to account for confounding factors.

In conclusion, the source material presents Claim 5 as an unsubstantiated assertion that oversimplifies peatland ecology. The evidence suggests that ceasing prescribed burning does not automatically lead to wetter peat or less heather; in fact, it may lead to drier conditions and increased wildfire risk.

The authors advocate for moving beyond generic claims and investing in site-specific, long-term, and methodologically sound research to inform future peatland management policies.

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