Peatland Fire Vulnerability

Peatlands are wetlands where partly decomposed plant remains accumulate as peat because waterlogged conditions slow decomposition. Draining them lowers the water table, exposing this carbon-rich organic soil to air and allowing it to dry. The resulting fire vulnerability comes from converting a normally wet carbon store into a deep, combustible fuel bed.

How drainage makes peat combustible

Water normally protects peat by limiting oxygen availability and absorbing heat. Drainage weakens both protections, although ignition still requires a heat source and sufficiently dry fuel.

• A lower water table exposes more peat above the saturated zone, increasing the thickness of the potentially combustible layer.
• As peat dries, less heat is needed to evaporate its moisture before combustion can become established.
• Air entering the exposed peat supplies oxygen for decomposition and combustion.
• Drought and high temperatures can intensify drying, making drained peatlands especially vulnerable when fires start in surface vegetation or nearby land.

Why fires persist beneath the surface

Unlike a vegetation fire that mainly consumes above-ground material, a peat fire can burn the soil itself. Peat commonly burns through smouldering combustion, a slow, flameless process that can continue within porous organic material.

• A thick peat deposit provides fuel below the surface, so the fire need not end when visible vegetation has burned.
• Surrounding peat insulates the burning zone, helping retain heat and sustain combustion.
• Smouldering requires less oxygen than flaming combustion and can therefore persist below the surface where air can still penetrate.
• Hidden hot spots may survive after visible flames disappear and can reignite surface vegetation.

Why suppression is difficult

Effective suppression requires cooling and wetting the burning peat, not merely extinguishing flames above it.

• Subsurface burning is difficult to locate, and surface-applied water may not reach every hot spot.
• If the water table remains low, surrounding dry peat continues to provide fuel, allowing fires to persist for weeks or months under suitable conditions.

Environmental consequences and prevention

Peat fires release stored carbon and produce persistent smoke containing fine particulate matter and carbon monoxide. They can also destroy habitat and remove organic soil.

• Preventing drainage and maintaining high water tables preserve peat's natural resistance to burning.
• Rewetting drained peatlands reduces the amount of dry, oxygen-exposed fuel, while ignition control remains necessary.