Wildfire in England in 2021 (Photo by Acacia England, U.S. Forest Service, www.flickr.com)
The warming and drying climate could increase the number of wildfires and subsequent carbon emissions in peatlands. Peatlands store about one third of the planet’s soil carbon, whilst only covering 4% of the world’s land surface. Peatlands at risk from climate change include high-latitude peatlands in the Northern Hemisphere where temperatures are rising faster compared to other areas across the globe.
UK case study
The impact of climate change on high-latitude peatland fire emissions was evaluated in a recent study by using the United Kingdom as an example. Peatlands cover 9% of the UK’s land-area. The authors quantified carbon emissions from wildfires from 2001–2021 for four distinguished land cover categories: ‘Forests and Woodlands’, ‘Moorlands and Heathlands’, ‘Peatlands’ and ‘Other Natural and Managed Lands’. They included data on biomass above and below the ground. For peatlands they selected areas with peats deeper than 0.5 m.
Peatland fires in the past 20 years
Peatland fires comprised about 25% of total average burned area from 2001–2021 in the UK. There was a lot of variation from one year to another in the annual carbon emissions by wildfires over this period. The emissions in 2003, for example, were nearly eightfold higher than the mean. That year also had the largest total burned area of this twenty-year period: about 50,000 ha.
Of all four distinguished land cover categories – ‘Forests and Woodlands’, ‘Moorlands and Heathlands’, ‘Peatlands’ and ‘Other Natural and Managed Lands’ – peatland fires dominated carbon emissions by wildfires in the UK. About 70% of the total UK wildfire carbon emissions were caused by the burning of organic soils in peatlands, at depths ranging between 0.9 and 8.0 cm.
Moorlands and heathlands contributed the most to the total burned area, 5600 ha per year on average. Peatlands burned on average 2530 ha per year. Emissions on moorlands and heathlands were primarily due to aboveground biomass combustion. The carbon density of this biomass is much lower than the carbon density of belowground biomass in peatlands. That’s why peatlands are UK’s dominant source of carbon emissions by wildfires. This dominant role is even more striking when one realizes that above-ground plant biomass will regrow between fires, making it unlikely that these fires will be a net source of emissions in the long term. Carbon loss from peat fires is more or less permanent.
More wildfires
The number of wildfires in the UK has increased year-on-year between 2014 and 2021; the trend is statistically significant. Fire seasons are also lengthening, from 1 to 4 months between 2011 and 2016 to between 6 and 9 months between 2017 and 2021. Fire season has become longer especially in Scotland. Scotland comprised about 45% of the total burned area in the UK in this period, and almost a quarter of all peatlands in the UK.
Two degrees global warming
In addition to the quantifications for 2001–2021, the authors made future projections of carbon emissions from peatland fires for a 2 °C warmer world. Future wildfires are projected to increase the UK’s carbon emission from peatlands by 61% compared with 2001–2021 emissions. The increase results from soil moisture changes, and therefore increased burn depths of peatlands. The authors conclude that ‘protecting peatlands from fires in the UK would be a cost-effective way to slow climate change by avoiding future emissions’.
The 61% increase is is based only on projected drier soil conditions and assumes no change in total burned area. An increase of burned area is to be expected, however, pushing carbon emissions up further. Besides, the study only included peatlands with peats deeper than 0.5 m. Shallow peats may also be at increased risk of wildfire and may therefore contribute to equally high carbon emissions in the future.
Source: Baker et al., 2025. Spikes in UK wildfire emissions driven by peatland fires in dry years. Environmental Research Letters 20.
