Wildfires are a semi-natural hazard, with most started accidentally from recreational or land management activities, or deliberately. Wildfires can start within forests or spread in from adjacent areas, such as grassland, heathland or moorland. Wildfires start more frequently in areas with high visitor numbers, near areas of socio-economic deprivation, and in areas close to public rights of way. Potential ignition sources include campfires, BBQs, hot oil or particles from machinery and vehicles, or power lines.

There are two periods of high wildfire risk: late winter-spring when there is dead-dry ground vegetation present (e.g., grass, bracken), overnight-frosts, dry periods with low daytime relative humidity; and summer, with hot and dry weather, including heatwaves and droughts. Wildfires during the latter are usually more intense and more damaging. The changing climate is likely to increase the risk of wildfires in both the late winter-spring and summer periods, and may extend the high-risk season into the autumn.

There are three main types of wildfires: surface fires, ground fires and crown fires. The most common is the surface fire, burning fuels such as heather, grass, bracken and gorse. Surface fires can burn fiercely, spread fast with long flames and at high fire intensity. There can be substantial growth of these fuels along roads and rides, before canopy closure, and after woods have been thinned. Ground fires consume peat and soil organic matter and threaten carbon stores. Smouldering peat fires are hard to extinguish and can re-kindle frequently.

Crown fires occur less frequently, during hot and dry summers, but are the most dangerous. They spread from surface fires, with ladder fuels, including tall shrubs, low tree canopies, standing deadwood and trees in poor health, and leaning windblown trees increase the risk of canopy fires.

Risks from wildfire can be reduced through good practice in forest design, planning and operations. Wildfire resilience measures can address potential ignitions sources, fuel load, minimise wildfire spread, protect assets and support response. Wildfire hazards and risks should be considered when planning a new woodland, and resilience measures included in existing design plans.

• Across the woodland area, plan regular fire breaks of sufficient width to the vegetation height to create discontinuous blocks. Roads, rides and natural features can be incorporated, and naturally resilient features, such as riparian areas, can be linked to fragment high-hazard areas.
• Protection areas should be planned in areas at high risk of fire entry or ignition and surrounding assets, including fire breaks and zones with prescribed management of ground vegetation, deadwood and brash. Highly flammable tree species and habitats should be avoided.
• To aid incident response, access roads with passing places, turning points, and a hard standing area should be incorporated, if possible, ensuring road & bridge weight limits support HGVs. Routes to open hills, access routes through boundaries, and gates through deer fences are important. Where possible, ensure sufficient water resources are available, such as fire ponds near the top of hills.
• Forest operations play a significant role in reducing wildfire risk. Operations should be timed to avoid high-risk conditions where possible. Vegetation and regeneration should be cleared in prescribed areas, during woodland establishment, along fire breaks, and regular, targeted swiping carried out along rides and roads. Brash and deadwood levels should be managed in high-risk zones, however deadwood is an important component of a properly functioning forest ecosystem, sustaining biodiversity and soil fertility, and outside high-risk zones, levels should be maintained according to UKFS guidelines.
• Regular tree health assessments should be carried out, with appropriate clearing and handling of diseased trees. The timely removal of wind throw, trees in poor health, under-performing stands should be planned, with the priority in high-risk areas.
• Access routes should be kept clear. Equipment and machinery should be maintained, and best practice in fuel use & storage followed.
• Incident response planning and fire maps can assist Fire and Rescue Services (FRS), reduce response times, aid suppression, and minimise impacts during an incident. Engagement with Fire and Rescue services, neighbouring landholders, and local wildfire groups can support land-scape scale resilience.

For further information see Forestry Commission Practice Guide 22 Building wildfire resilience into forest management planning.