FAQs: Carbon Emissions from Wildfires

Rob Beeson
Jul 29
10 min read

Wildfires are an important and growing factor in the carbon cycle. In high-carbon landscapes like the UK uplands, North American boreal forests, and Australian bush, wildfire management is now seen as integral to climate strategy.

Limiting wildfire carbon emissions - through better fire prevention, rapid suppression, ecosystem restoration, and climate change mitigation - will be crucial for meeting long-term emissions targets and preserving the carbon storage functions of the world’s forests and peatlands.

The FAQs below are supported by a number of sources including scientific reviews, peer reviewed research papers, government data and case studies from the UK and elsewhere.

How significant are wildfires as a source of carbon emissions, both globally and in the UK?
Why are peatland fires a disproportionately large source of carbon emissions in the UK?
How do carbon emissions vary by vegetation type and fire intensity?
What are the different components of wildfire carbon emissions, and how do they contribute to the overall impact?
How does climate change influence wildfire emissions and their long-term impact on the carbon cycle?
Can you provide examples of major international wildfire events and their carbon emissions?
What are the long-term impacts of increased wildfire severity and frequency on ecosystems' carbon storage capacity?
What are the key policy implications for managing wildfires in the context of climate change?

How significant are wildfires as a source of carbon emissions, both globally and in the UK?

Wildfires are a major source of carbon emissions worldwide, releasing carbon stored in vegetation and soils primarily as CO₂. Globally, they burn about 5% of the Earth's surface annually, emitting CO₂ equivalent to roughly 20% of annual fossil fuel emissions. In the past, this carbon was largely reabsorbed by regrowth, but increasing fire frequency and severity mean a net rise in atmospheric CO₂.

In the UK, while wildfires are small on a global scale, they still contribute significantly to national emissions, especially from peatlands. Between 2001 and 2021, UK wildfires released an average of about 44.8 kilotonnes of carbon per year (kt C/yr). However, this figure masks significant variability; for instance, in dry years like 2003, emissions soared to nearly 337 kt C. A substantial 300.8 kt of this came from soil carbon loss.

Peatland fires are particularly impactful, accounting for up to 90% of annual UK wildfire carbon emissions in some years, despite only making up about 25% of the total area burned. An estimated 800,000 tonnes of carbon were released from UK peatland fires between 2001 and 2021.

Why are peatland fires a disproportionately large source of carbon emissions in the UK?

Peatlands are critically important carbon stores, covering only about 9% of UK land but holding an estimated 3.2 billion tonnes of carbon. In a healthy state, they actively remove over three million tonnes of CO₂ from the atmosphere annually. However, when peat ignites, it releases vast amounts of carbon accumulated over centuries.

Despite accounting for only about 25% of the average burned area in the UK, peatland fires can be responsible for up to 90% of annual UK wildfire carbon emissions. This is because approximately 70% of all carbon released from UK fires originates from the combustion of carbon-rich peat soils, a figure that can rise to 81% in dry years.

For example, the 2018 Saddleworth Moor fire released an estimated 24,000 tonnes of carbon from deep peat, and the 2019 Flow Country fire released about 96,000 tonnes of carbon from peat alone, nearly eight times the UK's annual average wildfire carbon emissions.

The carbon lost from peat fires is considered "more or less permanent" because natural re-accumulation takes centuries, unlike heather moorland, which can recover and re-sequester carbon in about two decades. Drained peatlands are particularly vulnerable, experiencing carbon losses five to nine times greater than undrained peatlands under similar burn conditions.

How do carbon emissions vary by vegetation type and fire intensity?

The amount of carbon emitted per unit area of wildfire depends significantly on the fuel available and combustion completeness.

Peatlands (dry or drained): These are the most carbon-intensive, with severe fires releasing 50–100+ tonnes of carbon per hectare (t C/ha). In extreme cases like the North Sutherland wildfire, emissions reached 41.9-52.8 t C/ha, while drained peat bogs show 5-9 times greater loss than undrained.
Temperate Forests: High-intensity fires can release substantial carbon. Coniferous forest fires in Mediterranean Europe were found to emit ~56 tonnes of GHGs (CO₂ equivalent) per hectare, while broadleaf forests emitted ~44 t/ha. In North American forests, severe fires can emit 30–70 t C/ha, with fuel management significantly reducing these figures (e.g., ~68 t C/ha in untreated vs. ~30 t C/ha in thinned forests).
Shrublands: Mediterranean maquis shrublands can release ~30–40 t C/ha due to high biomass and volatile oils.
Grasslands and Heather Moorlands (above-ground): These have lower fuel loads. UK heather moorlands typically store 6–13 t C/ha in above-ground biomass, and direct carbon release from managed burns is around 1.03-2.01 t C/ha. Grassland fires typically consume only a few tonnes of carbon per hectare, ranging from 1.09-6.01 t C/ha in similar temperate meadow ecosystems. While per-hectare emissions are lower, their high frequency and large burned areas can make their total carbon contributions comparable to forests.

Wet, undrained peatlands typically have very low emissions (0-5 t/ha) if the peat remains moist.

What are the different components of wildfire carbon emissions, and how do they contribute to the overall impact?

Wildfire carbon emissions involve several components:

Direct Emissions from Biomass Combustion: This is the most immediate release, occurring as living or dead vegetation (trees, shrubs, grasses) burns. In non-peat fires, nearly all emissions come from this source. This carbon is released as CO₂, carbon monoxide, methane, and particulates, eventually oxidizing to CO₂ in the atmosphere.
Indirect Emissions from Soil Carbon Loss: This is a crucial component, especially in peatlands. In the UK, soil/peat combustion accounts for approximately 70% of total wildfire carbon emissions. This loss is long-term and difficult to recover, as peat re-accumulation takes centuries. Loss of peat also means loss of future carbon sequestration capacity.
Residual Char and Unburned Carbon: Not all carbon is immediately emitted. A fraction remains as charcoal (black carbon) or partially burned material. Charcoal is resistant to decay and can sequester carbon for centuries, slightly mitigating immediate atmospheric release. For example, ~4.3% of combusted biomass carbon in a UK moorland fire remained as charcoal, and ~14% of above-ground carbon remained unburned.
Post-Fire Emissions and Indirect Effects: Carbon dynamics continue after the flames subside. Fire-killed vegetation decomposes over years, releasing CO₂. Soil degradation and removal of vegetation can accelerate decomposition, leading to additional "indirect emissions." Furthermore, the loss of vegetation means "foregone carbon uptake" until regrowth occurs, effectively an indirect emission in the carbon budget. Smouldering in peatlands can continue for days to weeks underground, releasing carbon even after surface fires are controlled.
Other Environmental Factors: Wildfires also release other potent greenhouse gases like methane (CH₄) and nitrous oxide (N₂O), as well as aerosols like black carbon that impact air quality and climate. These broad impacts extend beyond direct carbon accounting to include soil degradation, biodiversity loss, and disruption of ecosystem services like water quality and timber production.

How does climate change influence wildfire emissions and their long-term impact on the carbon cycle?

Climate change is creating a dangerous positive feedback loop: hotter, drier conditions are lengthening fire seasons and increasing the risk and severity of wildfires, which in turn lead to greater carbon emissions, further contributing to global warming.

Lengthening Fire Seasons: In the UK, the fire season has expanded from 1-4 months (2011-2016) to 6-9 months in recent years, making conditions more conducive to ignition and spread.
Increased Emissions: Modeling indicates that with 2°C of global warming, carbon emissions from UK peatland fires could increase by at least 60%, releasing an additional 3.8 million tonnes of CO₂ annually. Drier peat, often linked to climate change and drainage, leads to deeper burns and significantly greater carbon loss.
Shift from Carbon Sink to Source: Historically, many ecosystems (like boreal forests) sequestered carbon. However, intensified wildfire regimes are causing sustained carbon losses, compromising their net sink function and transforming them into net carbon sources. Frequent, high-severity fires can also convert forests into lower biomass ecosystems (shrublands or grasslands), resulting in a net carbon loss from the landscape.
Impaired Recovery: Increased fire frequency means ecosystems may not fully recover between burns, leading to reduced long-term carbon storage capacity. While photosynthetic recovery can be relatively fast (75% of cases in less than 4 years), the re-establishment of long-term carbon stores takes much longer—centuries for peat, decades to centuries for forests, and even years for heather moorlands. This slow recovery, especially in conjunction with more frequent fires, contributes to a long-term net addition of CO₂ to the atmosphere.

Can you provide examples of major international wildfire events and their carbon emissions?

International wildfires demonstrate the immense scale of carbon emissions globally:

Portugal Wildfires (2017): This exceptionally severe season burned ~350,000 hectares of forests and shrubland, releasing approximately 4.93 million tonnes of CO₂ (equivalent to ~1.35 Mt C). This was roughly 15% of Portugal’s total CO₂ emissions for 2017.
European Wildfires (2022-2023): Drought and heat led to record activity, with 837,000 ha burned in 2022 and 504,000 ha in 2023. In 2023, EU wildfires emitted an estimated 20 Mt CO₂, roughly one-third of the annual CO₂ emissions from all EU aviation.
Canada Wildfires (2023): An unprecedented season saw ~18 million hectares burned, releasing an estimated ~480 megatonnes of carbon (Mt C), or nearly 1.76 billion tonnes of CO₂. This was five times Canada’s 20-year average wildfire carbon output and represented about 23% of global wildfire carbon emissions in 2023. Smoke plumes from these fires crossed the Atlantic, affecting air quality in Europe.
Australia "Black Summer" Bushfires (2019-2020): These massive fires burned over 12 million hectares, releasing about 715 Mt CO₂ to the atmosphere, more than double initial estimates. This is on the order of 200 Mt of carbon, greater than Germany’s total CO₂ emissions in 2019. Smoke even had climate feedback effects by fertilizing ocean algae blooms.
Siberia Wildfires (2021): Affected 9.3 million hectares, releasing 66.4 million tonnes of carbon (MtC). This was almost twice the long-term average, with 78% of emissions stemming from organic soil layers, highlighting the risk to vast permafrost carbon stores.

These examples illustrate that wildfire carbon emissions can occasionally rival industrial emissions in scale, making them a significant factor in global carbon budgets.

What are the long-term impacts of increased wildfire severity and frequency on ecosystems' carbon storage capacity?

The long-term impact of wildfires on carbon storage is complex but generally negative with increasing severity and frequency:

Reduced Biomass and Tree Cover: Frequent, high-severity fires prevent forests from fully recovering between burns. Studies show that areas with annual or very frequent fires can have significantly less wood biomass and fewer trees compared to unburned areas. This reduces the ecosystem’s long-term capacity to store carbon in live vegetation.
Ecosystem Type Shifts: Severe fires can remove soil seed banks or root stocks, leading to vegetation changes (e.g., conversion of forests to shrublands or grasslands). If an ecosystem shifts to a lower-biomass type, its equilibrium carbon stock is permanently lowered.
Compromised Carbon Sink Function: Ecosystems historically acting as carbon sinks (e.g., boreal forests) can transition to net carbon sources under intensified wildfire regimes. This means they emit more carbon through fire and decomposition than they absorb through regrowth.
Slow Soil Carbon Recovery: While above-ground biomass can regrow relatively quickly (decades), the recovery of soil carbon, especially in peatlands, takes centuries. Repeated fires can also prevent litter accumulation and promote soil oxidation, leading to long-term soil carbon reduction.
Persistent Carbon Deficit: Even decades after a large wildfire, affected areas may still have significantly less carbon in live trees compared to unburned areas due to slow regrowth and ongoing emissions from decay. This indicates a prolonged carbon deficit in the landscape.

In summary, increasing fire severity and frequency disrupt natural fire regimes, deplete carbon stocks, hinder ecosystem recovery, and can fundamentally alter landscapes, leading to a long-term net loss of carbon storage capacity.

What are the key policy implications for managing wildfires in the context of climate change?

The analysis highlights several critical policy implications for managing wildfires and mitigating their carbon footprint:

Prioritize Peatland Protection and Restoration: Given their disproportionate contribution to carbon emissions and the near-permanent loss of peat carbon, protecting and actively restoring peatlands (e.g., through aggressive re-wetting and peat moss inoculation) must be the highest priority for wildfire management in the UK and similar regions. This prevents catastrophic carbon releases and enhances sequestration.
Adopt Nuanced Fuel Management Strategies: A blanket approach to fire management is insufficient. Policy should differentiate by ecosystem type, peat depth, and fire intensity. This includes developing evidence-based guidelines for strategic fuel reduction through methods like carefully controlled burning in heather moorlands (where appropriate to reduce fuel loads) and mechanical cutting to prevent larger, more severe wildfires.
Enhance Monitoring and Early Warning Systems: The lengthening wildfire season necessitates year-round preparedness. Investment in advanced monitoring, forecasting, and early warning systems is crucial for anticipating and responding to wildfire threats across all seasons, particularly in vulnerable areas.
Integrate Wildfire Impacts into Broader Climate Policy: Wildfires are not isolated events; they are deeply intertwined with climate change, public health, and economic stability. Policy must adopt a holistic approach that integrates wildfire management into broader climate change mitigation and adaptation strategies, recognizing the cascading impacts on soil, biodiversity, water quality, and human health.
Foster International Collaboration: The global nature of wildfire emissions, particularly from large-scale events that affect atmospheric composition worldwide, underscores the need for enhanced international cooperation on research, monitoring, and shared best practices for wildfire management and climate resilience.
Improve Public Communication: Effective policy implementation requires public understanding and support. Communication efforts should emphasize the long-term, often hidden, costs of wildfires, especially the irreversible loss of soil carbon from peatlands, to underscore the urgency and importance of preventative measures and restoration efforts.

Key References

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