A new study led by the University of Cambridge has revealed that as our springs and summers get hotter and drier, the UK wildfire season is being stretched and intensified. More fires, taking hold over more months of the year, are causing more carbon to be released into the atmosphere as carbon dioxide.
Fires on peatlands, which are carbon-rich, can almost double global fire-driven carbon emissions. Researchers found that despite accounting for only a quarter of the total UK land area that burns each year, dwarfed by moor and heathland, peatland fires have caused up to 90% of annual UK fire-driven carbon emissions since 2001 – with emissions spikes in particularly dry years.
Peat only burns when it's hot and dry enough - conditions that are occurring more often with climate change. The peatlands of Saddleworth Moor in the Peak District, and Flow Country in northern Scotland, have both been affected by huge wildfires in recent years.
The researchers say land-managers can play an important role in helping to achieve Net Zero climate goals by keeping peatlands wet. This will reduce the likelihood of intense fires and their associated high carbon emissions.
Unlike heather moorland which takes up to twenty years to regrow after a fire, burnt peatland can take centuries to reaccumulate. The loss of this valuable carbon store makes the increasing wildfire frequency on peatlands a real cause for concern.
The researchers also calculated that carbon emissions from fires on UK peatland are likely to rise by at least 60% if the planet warms by 2oC.
The findings, which are broadly relevant to peatlands in temperate climates, are published today in the journal Environmental Research Letters.
"We found that peatland fires are responsible for a disproportionately large amount of the carbon emissions caused by UK wildfires, which we project will increase even more with climate change," said Dr Adam Pellegrini in the University of Cambridge's Department of Plant Sciences, senior author of the study.
He added: "Peatland reaccumulates lost carbon so slowly as it recovers after a wildfire that this process is limited for climate change mitigation. We need to focus on preventing that peat from burning in the first place, by re-wetting peatlands."
The researchers found that the UK's 'fire season' - when fires occur on natural land - has lengthened dramatically since 2011, from between one and four months in the years 2011-2016 to between six and nine months in the years 2017-2021. The change is particularly marked in Scotland, where almost half of all UK fires occur.
Nine percent of the UK is covered by peatland, which in a healthy condition removes over three million tonnes of carbon dioxide from the atmosphere per year.
The researchers estimate 800,000 tonnes of carbon were emitted from fires on UK peatlands between 2001 and 2021. The 2018 Saddleworth Moor fire emitted 24,000 tonnes of carbon, and the 2019 Flow Country fire emitted 96,000 tonnes of carbon from burning peat.
To get their results, the researchers mapped all UK wildfires over a period of 20 years – assessing where they burn, how much carbon they emit, and how climate change is affecting fires. This involved combining data on fire locations, vegetation type and carbon content, soil moisture, and peat depth. Using UK Met Office data, the also team used simulated climate conditions to predict how wildfires in the UK will change in the future.
The study only considered land where wildfires have occurred in the past, and did not consider the future increases in burned area that are likely to occur with hotter, drier UK summers.
Rewetting peatlands to protecting the carbon they store will require land managers to be incentivised – the researchers say this won't be easy, but the impact could be big.
"Buffering the UK's peatlands against really hot, dry summers is a great way to reduce carbon emissions as part of our goal to reach net zero. Humans are capable of incredible things when we're incentivised to do them," said Pellegrini.
An average of 5,600 hectares of moor and heathland burns across the UK each year, compared to 2,500 hectares of peatland.
