Forestry England Says New Forest Fire Slowed on Ground Managed by Burning
Quick summary
A New Forest wildfire slowed when it reached ground Forestry England had previously managed with controlled burning.
Nearly 100 hectares of heath, bog and woodland burned, including ancient oak and beech.
Winter prescribed burns clear surface fuel without reaching the soil or seed bank.
What happened on the ground is consistent with published research.
A wildfire that burned nearly 100 hectares of the New Forest this summer slowed when it reached ground that had previously been managed by controlled burning, a Forestry England manager has said.
Leanne Sargeant, Nature Recovery Manager at Forestry England, was speaking to presenter Matthew Wilson at the fire site in an episode of BBC Radio 4's Gardeners' Question Time (feature starts at 12m 15s) recorded at Minstead Village Hall in the New Forest.
Leanne said the fire's behaviour changed as it crossed the managed ground and that crews were able to contain it more easily there. "There wasn't the fuel source there because we'd managed it previously," she said.
The fire destroyed dry heath, bog and woodland, including ancient woodland. Because the summer had been so dry, it burned down into the bog and consumed peat, which Leanne said would not recover quickly.
Oak and beech trees of 300 and 400 years old were left with singed canopies and burnt roots, and she said she expected some of them to die. Firefighters kept the fire from taking the whole woodland block, leaving intact trees standing between the burnt sections.
Asked whether the intensity of the fire had worsened the damage, Leanne contrasted it with the prescribed burns Forestry England carries out on the heath. Those are done in winter, when the ground is wet. "We do it in the winter, so the soil is wet," she said.
She described a fast burn across the surface that removes mature heather without reaching the soil, and said the same technique is used to break up blocks of gorse that have grown too mature. Green growth is visible straight away: "as soon as they finish burning, there's green on the ground underneath."
A summer wildfire behaves differently, burning down into the soil and destroying the seed bank. Heath carries only a centimetre or two of topsoil, Leanne said, and wind was lifting ash and soil off the burnt ground in dust devils on the day of the recording.
Fuel load and fire severity
What Leanne described on the ground is consistent with the published evidence on how fuel affects fire behaviour.
A field study of British peatland wildfires found that sites carrying more surface fuel before ignition burned more completely and at higher severity (Davies et al., 2016, Philosophical Transactions of the Royal Society B). Modelling of heather-dominated ground reaches a similar conclusion, finding that reducing biomass lowers both the likelihood of a wildfire and its severity when one occurs (Santana and Marrs, 2016).
The other side of this is that fuel builds up on ground nobody manages. Aerial photograph monitoring in the Peak District found that more than 70% of the burnable area went unburned across a 22-year study period, with the authors noting the resulting fuel build-up and increased wildfire risk (Douglas et al., 2015, Ecological Indicators).
