FAQs: Limitations of Rewetting as a Sole Wildfire Mitigation Strategy

The sources used to produce these FAQs reinforce that holistic land and fire management - combining hydrological restoration with active fuel management and adaptation to local conditions - is essential.

Rewetting is a crucial piece of the puzzle for peatland wildfire mitigation, but on its own it rarely provides a sufficient safeguard against the complex, multifactorial threat of wildfires in a changing climate.

• What is peatland rewetting and how does it generally help with wildfire risk?

• Why is rewetting alone not a complete solution for wildfire prevention in peatlands?

• How do vegetation dynamics and fuel loads impact the effectiveness of rewetting?

• What role do climate change and drought conditions play in undermining rewetting efforts?

• What are some of the unintended consequences or challenges that can arise from rewetting efforts?

• Provide examples of case studies that illustrate the limitations of rewetting alone

• What is "Integrated Fire Management" (IFM) and why is it recommended for peatlands?

• What are the key recommendations for a holistic approach to peatland wildfire management?

What is peatland rewetting and how does it generally help with wildfire risk?

Peatland rewetting is a restoration strategy that involves raising water tables, often by blocking drainage ditches, to restore the natural wetness of degraded peatlands. This process encourages the growth of water-loving vegetation like Sphagnum mosses, which retain moisture and make the ecosystem more fire-resilient.

Rewetting primarily helps by reducing the flammability of the peat itself. Wet peat burns less readily than drained peat, and a high water table is crucial for preventing deep, smoldering peat fires that release vast amounts of stored carbon. Case studies, such as those in Russia's Meshchera National Park and areas in mid-Wales and Scotland, have shown that rewetted areas can act as effective firebreaks, limiting fire spread and severity.

Why is rewetting alone not a complete solution for wildfire prevention in peatlands?

While rewetting is beneficial for increasing peat moisture and reducing deep peat fires, it has significant limitations as a standalone wildfire prevention strategy. Several factors undermine its effectiveness:

• Delayed Vegetation Change and Fuel Loads: Restoring a fully functioning, fire-resistant bog ecosystem can take decades. In the interim, previously drained sites often remain dominated by dry, highly flammable vegetation like heather (Calluna vulgaris) and purple moor grass (Molinia caerulea), which can carry intense surface fires. Rewetting alone may not rapidly re-establish moisture-retaining moss cover, leaving ample fuel above ground.

• Drought and Climate Extremes: Severe droughts and heatwaves, exacerbated by climate change, can override rewetting efforts. Peatlands that are normally wet can dry dramatically, making both surface vegetation and underlying peat vulnerable to ignition, as seen in the 2018 Saddleworth Moor fire and the 2019 Flow Country wildfire.

• Site-Specific Limitations: The effectiveness of rewetting varies with local conditions like topography (e.g., steep slopes shed water quickly) and geology (e.g., underlying rock permeability), making it difficult to maintain consistent wetness in all areas.

• Time Lags and Seasonal Windows: Even where rewetting works, there's a long transition period before the habitat becomes truly fire-resistant. During this time, high fuel loads can persist, and water table levels fluctuate seasonally, leaving sites prone to fire in dry seasons.

How do vegetation dynamics and fuel loads impact the effectiveness of rewetting?

Degraded peatlands often have dense stands of highly flammable vegetation, such as heather and purple moor grass, which accumulate as significant "fuel loads." While rewetting aims to suppress these species and encourage less combustible Sphagnum mosses, this ecological transition is inherently slow, taking many years or even decades.

During this prolonged transition, even in rewetted areas, these dry, fire-prone vegetation types can persist. This means that a high risk of surface fires remains, as the fire can spread rapidly across the landscape through these fuels, even if the underlying peat is wet.

Active interventions, like spreading Sphagnum fragments, are often needed to accelerate the establishment of moisture-retaining moss cover and outcompete dry-loving vegetation, rather than relying solely on natural processes.

What role do climate change and drought conditions play in undermining rewetting efforts?

Climate change is a major and increasing driver of wildfire risk in peatlands. Hotter, drier summers and an extended wildfire season mean that peat, which only burns when sufficiently dry and hot, is more frequently reaching critical flammability levels.

This intensification of drought conditions can overwhelm rewetting efforts. Even peatlands designed to be wet can experience significant drying of both surface vegetation and the underlying peat during extreme droughts. This leads to deeper peat fires and the release of vast quantities of stored carbon, which can take centuries to reaccumulate.

Projections suggest that a 2°C global warming could increase fire-driven carbon emissions from UK peatlands by at least 60% due to increased burn depths. This highlights that rewetting, while beneficial, cannot fully buffer against the most extreme climate events, necessitating additional prevention and suppression measures.

What are some of the unintended consequences or challenges that can arise from rewetting efforts?

While rewetting offers significant benefits, it's not without potential challenges and unintended consequences:

• Increased Methane Emissions: While primarily reducing CO2 emissions from peat decomposition, rewetting can lead to increased emissions of methane (CH4), another potent greenhouse gas. Although the CO2 benefits generally outweigh the CH4 increase, it's an important consideration for the overall greenhouse gas balance.

• Complex Vegetation Shifts: The ecological outcomes of rewetting can be unpredictable. While some studies show an increase in wetland plants, others find no significant effect or even a reduction in certain species. The desired shift away from flammable vegetation (like purple moor grass) may not be uniform or immediate across all species.

• False Sense of Security: Incomplete or uneven rewetting can create a false sense of security, leading managers to believe an area is protected when it may still be vulnerable to fire, particularly during dry spells.

• Hydrological Management Needs: Achieving optimal peatland restoration requires careful and precise hydrological management, with the water table ideally just below or a few centimeters above the peat surface, rather than simply allowing deep flooding.

Provide examples of case studies that illustrate the limitations of rewetting alone

Several case studies highlight the insufficiency of rewetting as a standalone strategy:

• Marsden Moor, UK (2019, 2020, 2021 wildfires): Despite significant rewetting efforts, this peat-rich upland suffered multiple wildfires during dry weather. High fuel loads (dead bracken and grass) due to the cessation of controlled burning helped carry fires over rewetted peat, necessitating active vegetation management (cutting firebreaks, grazing) and rapid firefighting response.

• Riau Province, Indonesia (2015-2021 fires): Large-scale rewetting reduced extreme fire events by about 40% and burned area by 5%. However, severe fires still occurred and persisted longer during extreme droughts (e.g., El Niño years), demonstrating that rewetting mitigated but did not eliminate risk under the worst climate conditions.

• Saddleworth Moor (2018) and Flow Country (2019), UK: These major wildfires scorched normally wet blanket bogs during extreme drought conditions, challenging the notion that simply blocking ditches is enough to protect uplands from fire.

• Northern Europe and Canada (Granath et al., 2016): Research showed that rewetting improved moisture but was only truly effective in reducing deep fire risk if accompanied by the active re-establishment of a Sphagnum moss layer. Without active introduction of wet species, rewetted peatlands could still dry near the surface and remain susceptible to fire.

What is "Integrated Fire Management" (IFM) and why is it recommended for peatlands?

Integrated Fire Management (IFM) is a comprehensive, multi-faceted approach to wildfire management that goes beyond reactive suppression. It systematically combines fire prevention, response, and recovery strategies, while integrating ecological, socio-economic, and cultural factors.

IFM is recommended for peatlands because relying solely on rewetting is insufficient to address the complex, multifactorial threat of wildfires, especially with climate change. IFM provides a robust framework that accounts for:

• Fuel Management: Proactively reducing flammable materials through controlled burns (where appropriate), mechanical treatments (thinning, clearing), or grazing.

• Wildfire Response and Prevention: Maintaining readiness for and effective response to fires, alongside public education and initiatives to reduce human-caused ignitions.

• Post-Fire Recovery: Activities to stabilize and restore affected landscapes.

• Adaptive Planning: Recognizing that fire management needs to be dynamic and tailored to local conditions, rather than a one-size-fits-all approach.

IFM emphasizes proactive measures ("Readiness" and "Reduction" account for ~80% of its focus) and strategic planning, recognizing that fires don't respect administrative boundaries. It provides a more realistic and effective strategy for long-term resilience.

What are the key recommendations for a holistic approach to peatland wildfire management?

A holistic approach to peatland wildfire management must combine hydrological restoration with active land management and adaptive planning. Key recommendations include:

• Fuel Load Management: Implement methods like controlled burning (where suitable and safe), mowing, or strategic grazing to reduce combustible surface vegetation. Creating defensible "fuel break" zones is also important.

• Active Vegetation Restoration: Actively plant or seed fire-resilient, peat-forming species like Sphagnum mosses to accelerate the transition to a wetter, less flammable ecosystem. This helps cover bare, dry peat rapidly.

• Hydrological Maintenance: Rewetting is not a one-time fix. It requires ongoing maintenance, such as ensuring drainage ditches remain blocked, and potentially additional engineering (e.g., pond creation, pumping during extreme droughts) to maintain water levels during critical periods.

• Fire Preparedness and Monitoring: Even with comprehensive management, wildfires can occur. This necessitates community education to prevent ignitions, early warning systems based on fire weather indices, and well-trained wildfire response teams. Wildfire scenarios should be integrated into land management plans.

In essence, rewetting should be viewed as a crucial tool within a broader fire management toolkit, rather than a singular solution. An integrated strategy that addresses both the hydrological and fuel aspects of the landscape, while adapting to the pressures of climate change, is essential for creating truly wildfire-resilient uplands.

Key References

• Granath, G. et al. (2016, Northern Europe/Canada) - Scientific Reports 6:28498: Showed that raising water tables in drained peatlands reduces deep peat fire risk only if a new Sphagnum moss layer is established; rewetting alone was insufficient unless water table remained at the surface, so active restoration measures are needed

• Santikayasa, I.P. et al. (2023, Riau, Indonesia) - Sustainability 15(3):2169: Found large-scale rewetting cut extreme peat fire occurrences by ~40% and burned area by 5%, but did not prevent all severe fires; during drought (El Niño 2015, 2019) extreme fire events still occurred and lasted longer on rewetted peatlands. Demonstrates partial effectiveness of rewetting and the overriding influence of extreme climate events.

• Heinemeyer, A. (2024, UK) - Interview in POSTnote 717 & SEI York feature: Warns against assuming rewetting alone suffices. Notes that some advocate banning all burning in favor of rewetting, but “many others disagree… Rewetting on its own may not work in certain situations” (e.g. steep slopes). Emphasizes evidence that unmanaged vegetation can increase risk and that site-specific approaches (including controlled burning, cutting, or grazing) are vital.

• Wentworth, J. & Tasker, S. (2024, UK) - Parliamentary Office of Science & Technology, POSTnote 717: Summarizes that wildfire frequency/severity is rising with climate change and that stakeholders debate the merits of peatland rewetting vs. other land-management for wildfire resilience. Highlights that wildfire risk should be built into land management planning, implying no single solution fits all.

• Allen, K.A. et al. (2016, UK) - Philosophical Transactions of the Royal Society B 371: Discusses fire in UK peat moorland management. Notes that even very wet bogs can burn given the right conditions (e.g. dry weather before spring green-up), illustrating that high water tables don’t guarantee protection if surface fuels are dry. Stresses the need to distinguish fire regimes by severity and consider long-term ecosystem responses.

• National Trust Marsden Moor Case (2019–2022, England) - Organizational reports: Demonstrates a real-world scenario where rewetting and no-burning policy has been supplemented with active interventions (cutting firebreaks, reseeding moss, adjusting grazing) after recurring wildfires

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