Review Challenges Claims of Biodiversity Loss from Controlled Burning

A major scientific review critically examines ten common claims regarding the effects of prescribed heather burning on peatlands in the UK, with “Prescribed heather burning causes loss of biodiversity” being the tenth claim reviewed.

The authors, including Dr. Andreas Heinemeyer, consider the claim to be a generalization that is not supported by sufficient evidence and requires significant contextualization. The review of this claim highlights the complexity of the issue and the mixed results found in the existing evidence base.

Discussion of Claim 10: Biodiversity Loss

The review critiques the claim that prescribed burning causes biodiversity loss for several key reasons:

• Generalization and Lack of Evidence: The statement is considered too generic. There is very little evidence to support claims of "significant adverse impacts" from prescribed burning, as has been stated in some position papers. The overall evidence base shows varied impacts on nearly all ecosystem aspects, including biodiversity, with no grounds for a generalized conclusion of negative effects.

• Mixed and Context-Dependent Results: The evidence indicates mixed outcomes depending on the experimental setup, site context, and time scales involved. A review by Holland et al. (2022) found no evidence to generalize overall negative impacts, even on Sphagnum moss. Often, any negative impacts reported are short-lived and should be viewed within the larger landscape context of a patchwork of different vegetation ages and communities.

• Importance of Management Planning: The impacts on biodiversity are not inherent to burning itself but depend on how it is implemented. When prescribed burning is carefully planned - considering the specific peatland characteristics and conservation goals - it is possible to minimize negative impacts while promoting positive biodiversity outcomes. This requires proper strategies, including monitoring and adaptive management.

• 'Winners and Losers': Any management choice, including prescribed burning, will result in "winners and losers" among species. Biodiversity impacts need to be contextualized against the conservation status of various species, including important bird species like curlew, lapwing, and golden plover, not just plants.

• Scale is Crucial: The impacts of burning on biodiversity are dependent on temporal and spatial scales. Short-term, plot-level studies may not capture the full picture. For instance, prescribed burning can increase habitat diversity at the ecosystem level (beta diversity), which in turn likely increases overall diversity at the landscape scale (gamma diversity) by creating a mosaic of habitats. These larger-scale benefits are often missed in short-term assessments.

Claim 10 in the Larger Context of the Evidence Review

The discussion of Claim 10 fits into the broader theme of the review, which critically examines ten common claims about prescribed heather burning on UK peatlands. The authors argue that many of these claims, frequently made by governmental and non-governmental organizations, are ambiguous, generalized, or not based on robust evidence.

The critique of Claim 10 shares commonalities with the critiques of the other nine claims:

1. Poor Definitions: The term "biodiversity loss" is ill-defined and too broad. It is essential to specify which species or groups are being discussed and to consider the site and time dependence of any changes. This mirrors issues with terms like 'peat-forming' (Claim 3).

2. Methodological Flaws: Evidence supporting biodiversity loss often comes from studies with limitations, such as a lack of proper controls or consideration of confounding factors. The authors repeatedly call for more robust "Before-After-Control-Impact" (BACI) studies at multiple sites and catchment scales to properly identify causation.

3. Scale Mismatches: As with claims about flooding (Claim 8) and carbon loss (Claim 1), findings from small plots or short-term studies are often improperly extrapolated to make landscape-scale or long-term conclusions.

4. Site-Specificity: The impact of burning is highly dependent on site-specific conditions, management history, and conservation objectives. A generalized statement about biodiversity loss fails to account for this critical variability, a problem also identified for claims about carbon balance (Claim 1) and hydrology (Claims 4, 5, 7, 8).

In conclusion, the authors position Claim 10 as another example of a simplified and potentially misleading narrative surrounding prescribed burning. They argue that the available evidence is insufficient, contradictory, and too context-dependent to justify a blanket statement that burning causes biodiversity loss.

Instead of a ban, they recommend a more nuanced, evidence-based approach that uses well-planned management trials to understand the risks and benefits for different species and ecosystems.

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