6,000 Years of Heather and Fire: Why the ‘Recent Management’ Claim Doesn’t Stack Up

A major scientific review critically examines ten common claims regarding the effects of prescribed heather burning on peatlands in the UK, with "Fire and heather dominance are a result of recent management changes", being the second claim reviewed.

The authors, including Dr. Andreas Heinemeyer, consider the claim to be unsubstantiated and too generic. The evidence review critically examines this assertion, placing it within the larger context of a debate over prescribed heather burning on UK peatlands, where many common statements are found to be ambiguous or incorrect.

Evidence and Counter-Evidence

The review challenges the idea that fire and heather dominance are recent phenomena primarily driven by modern management practices like grouse moor management. The review of evidence suggests a much longer and more complex history:

• Defining 'Recent' is Problematic: A key issue with the claim is the ambiguity of "recent management". While prescribed burning for grouse moors intensified over the last 200 years, peat core evidence indicates a much longer history of both fire and heather on UK peatlands.

• Long History of Heather Dominance: Palaeoecological records from peat cores show that heather-dominated vegetation, indicated by high pollen counts and plant remains, has been a feature of several UK upland peatland sites for approximately the last 6,000 years. This directly contradicts the notion that heather dominance is a recent development.

• Ancient Evidence of Fire: Similarly, peat core studies have found frequent charcoal layers throughout deep peat profiles across the UK. These records support the view that fires, whether from natural wildfires or intentional burning by humans, have occurred on many UK upland peatlands throughout the Holocene.

• Multiple Drivers of Vegetation Change: The evidence suggests that shifts in vegetation, including cyclical changes between Sphagnum, grass, and heather cover over the last millennium, have complex causes. It is often unclear what the key drivers were, with factors like grazing, drainage, atmospheric pollution, and climate change likely playing significant roles alongside burning. For example, industrial pollution is known to have severely reduced Sphagnum cover in the UK's Peak District.

• Correlation vs. Causation: The review cautions against assuming a simple cause-and-effect relationship. For instance, a negative relationship between Sphagnum and heather cover in peat profiles does not automatically mean one caused the decline of the other, as other factors like climate could be responsible. The relationship is complex: it's unclear if the presence of heather drives burning, or if burning leads to increased heather cover.

In summary, the palaeoecological record strongly indicates that both fire and heather dominance are unlikely to be exclusively recent phenomena within UK peatlands. The key drivers of historical vegetation changes remain largely unknown, making it difficult to attribute them solely to recent management.

Context within the Ten Key Claims

The review of Claim 2 is part of a broader critical assessment of ten common claims made about prescribed heather burning by governmental organizations, NGOs, media, and scientists. The analysis of Claim 2 connects to several other claims in the review:

• Claim 3 (Burning reduces Sphagnum and peat formation): By showing that heather has long been a significant component of peatlands and a peat-forming species, the discussion on Claim 2 provides context for challenging the idea that Sphagnum is the sole or primary peat-former.

• Claim 4 (Rewetting reduces heather dominance): Understanding that heather has persisted for millennia across various conditions undermines the simplistic assumption that rewetting alone will eliminate it.

• Overall Theme of Insufficient Evidence: Like many of the other nine claims, the paper concludes that Claim 2 is not supported by robust evidence. The authors highlight common problems across the evidence base, such as the need for better definitions (e.g., what constitutes 'recent'), consideration of confounding factors, and a site-by-site approach to understanding ecological history.

The authors recommend that to properly assess this claim, there is a need to better define and contextualize what "recent" management means on a site-by-site basis and to fully consider the multiple confounding factors that influence vegetation change.

This aligns with their overarching conclusion that much of the debate around peatland management is based on "unverified assertions and misleading arguments" rather than robust, applicable evidence.

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