The devastating fire at Killarney National Park last April produced greenhouse gas emissions equivalent to the annual mileage of 7,600 cars.
That’s despite burning just half the land area originally feared.
The findings come from a project which for the first time accurately quantifies the damage caused by wildfires to the landscape and climate.
With roughly 2,300-2,800 wildfires in Ireland each year, the implications for efforts to cut national emissions are massive.
Researchers have found that fires have been under-reported and their greenhouse gas emissions likely under-counted.
That is partly because the true number of incidents was not known but also because information on the type of vegetation burnt was vague.
They have used new maps being drawn up for Ireland that identify the exact kind of land cover, and a specially-developed satellite observation system.
The analysis is being carried out by FLARES (Fire, Land and Atmospheric Remote Sensing of Emissions), a project led by scientists at University College Cork (UCC).
Dr Fiona Cawkwell of UCC’s geography department said satellite data was being captured and used in the project with far more precision than the European system previously relied upon.
“It’s a system that works really well for example in the Mediterranean where you have large, intense fires and clear skies but a lot of the Irish fires are quite small and if they happen under thick cloud cover they are much harder to detect so a lot of the smaller fires are being missed,” she said.
The Irish countryside also suffers smouldering fires beneath the visible vegetation which can continue for weeks virtually undetected from above.
Two of the case studies the FLARES team have completed to date cover seven years of fires in the Blackstairs Mountains in counties Wexford and Carlow, and the Wicklow Mountains.
They found burn scars from 271 fires in the Blackstairs Mountains where just 195 fires were reported.
The burned areas were largely covered in dry heath, but 16 other habitats were affected from bracken and broad-leaved forest to hedgerows and several types of grassland.
Collectively, those fires emitted almost 41,000 tons of greenhouse gases (GHG), mostly carbon dioxide but also small amounts of methane and nitrous oxide along with carbon monoxide and nitrogen dioxide which react with other gases to indirectly cause warming.
That is roughly the equivalent of 9,000 fossil fuel cars, each driven for 12,000 miles – the annual distance for the average motorists pre-Covid.
In the Wicklow Mountains, 300 burn scars were found, just slightly more than the 286 fires reported, with blanket bog the main vegetation burned but 19 other types of habitat also affected.
GHG emissions there totalled just over 90,000 tonnes, the equivalent of around 19,700 cars with a total annual driving of more than 227 million miles.
Dr Dean Venables of the chemistry department arranged for laboratory burning experiments of particularly Irish vegetation such as gorse to establish more accurately how much GHG they produce.
“The methodology is now quite well established so this can be applied relatively quickly to the rest of the country,” he said. “From that it will be possible to estimate total burn emissions for Ireland with a pretty good level of accuracy.”
The FLARES project winds up next summer and Dr Cawkwell said only a few case studies would be completed by then but other state agencies could use the methods to improve the annual inventory of GHG emissions.
“The burn figures in the national inventory are best estimates at the moment but it’s becoming increasingly important to know as much as we can about our emissions,” she said.
“When we hear about wildfires, we think of California or Australia or Greece.
"Ireland’s tend to be much smaller but even though the Killarney burn area turned out to be 1,400 hectares or about half the 2,500-3000 hectares originally reported, it all adds up.”
Wildfires are a divisive issue every year in this country as farmers are allowed carry out controlled burning at certain times but fires often get out of control and burn natural habitats.
Many other fires happen outside the legal burning period with suspicions that they are deliberate or caused through carelessness.
The FLARES team are not examining causes but Dr Cawkwell said she hoped their research would help inform debate on the issue.
The project is also gathering data on particulate matter, the tiny particles of soot and burnt material that are emitted from fires and which can cause respiratory problems when breathed in.
“Emissions have both health impacts and climate impacts,” said Dr Venables.
“We need to pay attention to all our emissions, not just those associated with direct human activities but also these types of activities such as fires which may be natural or partly or a little bit below the radar.”