How do underground peat fires keep burning after a wildfire is out?

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1. 1

   Smouldering wildfires in peatlands, forests and the arctic: Challenges and perspectives.

   Current opinion in environmental science & health (Rein & Huang)Published Dec 1, 2021Checked Oct 11, 2026

   “Wildfires can be divided into two types, flaming or smouldering, depending on the dominant combustion processes. Both types are present in most wildfires, and despite being fundamentally different in chemical and physical terms, one transitions to the other. Traditionally, science has focused on flames, while smouldering is often misinterpreted. But smouldering wildfires are emerging as a global concern because they cause extensive air pollution, emit very large amounts of carbon, are difficult to detect and suppress, and could accelerate climate change. Central to the topic are smouldering peat fires that lead to the largest fires on Earth. Smouldering also dominates the residual burning after flames have died out and firebrand ignition. Finally, smouldering is an important part of Arctic wildfires, which are increasing in frequency. Here, we present a scientific overview of smouldering wildfires, the associated environmental and health issues, including climate change, and the challenges in prevention and mitigation.”

2. 2

   Peat (Wikipedia)

   WikipediaPublished Oct 10, 2026Checked Oct 11, 2026

   “Peat is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. Sphagnum moss, also called peat moss, is one of the most common components in peat, although many other plants can contribute. The biological features of sphagnum mosses act to create a habitat aiding peat formation, a phenomenon termed 'habitat manipulation'. Soils consisting primarily of peat are known as histosols. Peat forms in wetland conditions, where flooding or stagnant water obstructs the flow of oxygen from the atmosphere, slowing the rate of decomposition. Peat properties such as organic matter content and saturated hydraulic conductivity can exhibit high spatial heterogeneity. Peatlands, particularly bogs, are the primary source of peat; although less common, other wetlands, including fens, pocosins and peat swamp forests, also deposit peat. Landscapes covered in peat are home to specific kinds of plants, including Sphagnum moss, ericaceous shrubs and sedges.”

3. 3

   Conserving mire ecosystems: linking flammability and moisture content of peaty substrates.

   The Science of the total environment (Mason et al.)Published Oct 21, 2025Checked Oct 11, 2026

   “We sought to quantify the change in combustion risk across moisture gradients. We used samples within four undisturbed mire locations in southeastern Australia. Prior to laboratory simulations, we measured moisture, bulk density and organic matter for each sample. We then applied smouldering or flaming (either 35 kWm-2 or 75 kWm-2 intensity) ignition and observed moisture thresholds for substrate combustion. We assessed the combustion risk associated with underground mining using field data from moisture probes deployed in mined and unmined mires. We found that the probability of substrate combustion was negatively related to moisture levels for both smouldering and flaming ignition types. In the case of flaming ignition, high intensity fire had increased risk of burning at higher substrate moisture than moderate-intensity fire. When we compared moisture thresholds for substrate combustion with field moisture conditions, we found that underground mining more than doubled the risk of substrate burning for all ignition types. Anthropogenic disturbances that disrupt natural hydrological regimes and reduce substrate moisture, concurrently increase fire risk in the landscape.”

4. 4

   Impact of Snow on Underground Smoldering Wildfire in Arctic-Boreal Peatlands.

   Environmental science & technology (Qin et al.)Published Feb 6, 2025Checked Oct 11, 2026

   “Despite the critical role of fire-snow interactions in these processes, our understanding of them remains limited. Herein, we conducted small-scale outdoor experiments (20 × 20 × 20 cm3) at subzero temperatures (-5 ± 5 °C) to investigate the impact of natural snowfall and accumulated snow layers (up to 20 cm thick) on shallow smoldering peat fires. We found that even heavy natural snowfalls (a maximum water equivalent snowfall intensity of 1.1 mm/h or a 24 h accumulated snowfall water equivalent precipitation of 7.9 mm) cannot suppress a shallow smoldering peat fire. A thick snow cover on the peat surface can extract heat from the burning front underneath, and the minimum thickness of the snow layer to extinguish the peat fire was found to be 9 ± 1 cm at subzero temperatures, agreeing well with the theoretical analysis. Furthermore, larger-scale field demonstrations (1.5 × 1.5 m2) were conducted to validate the small-scale experimental phenomena. This work helps us to understand the interactions between fire and snow and reveals the persistence of smoldering wildfires under cold environments.”

5. 5

   Tropical peat composition may provide a negative feedback on fire occurrence and severity.

   Nature communications (Crawford et al.)Published Aug 27, 2024Checked Oct 11, 2026

   “Loss of peat through increased burning will have major impacts on the global carbon cycle. In a normal hydrological state, the risk of fire propagation is largely controlled by peat bulk density and moisture content. However, where humans have interfered with the moisture status of peat either via drainage, or indirectly via climate change, we hypothesise that its botanical composition will become important to flammability, such that peats from different latitudes might have different compositionally-driven susceptibility to ignition. We use pyrolysis combustion flow calorimetry to determine the temperature of maximum thermal decomposition (Tmax) of peats from different latitudes, and couple this to a botanical composition analysis. We find that tropical peat has higher Tmax than other regions, likely on account of its higher wood content which appears to convey a greater resistance to ignition. This resistance also increases with depth, which means that loss of surface peat in tropical regions may lead to a reduction in the subsequent ignitability of deeper peat layers as they are exposed, potentially resulting in a negative feedback on increased fire occurrence and severity.”

6. 6

   Widespread peat carbon losses driven by the 2025 Scottish megafire.

   Nature geoscience (Schoenecker et al.)Published May 20, 2026Checked Oct 11, 2026

   “Drier and warmer climates have allowed fires to increasingly burn carbon-dense peatland ecosystems. Here we document a 2025 Scottish megafire in the UK, which spread rapidly and burned severely across peatlands in Scotland with anomalously low soil moisture, emitting 38,600 MgC (25,200-119,000 MgC). Peat combustion contributed nearly 85% of total emissions, suggesting drier climates increase fire emissions from peat, which can require decades to centuries to recover.”

7. 7

   How drones are hunting fires hidden beneath the Cairngorms

   BBC NewsPublished Oct 10, 2026Checked Oct 11, 2026

   “Dramatic flames from the huge Cairngorms wildfire in July have disappeared - but hot spots can continue to burn beneath the earth.”