We have seen lots of news reports about wildfires recently, with catastrophic scenes from many countries including Greece, California and Australia. Maps in the UN report Spreading Like Wildfire show that the area of land burned by wildfire has increased in parts of the UK in recent years.  Surrey Fire and Rescue Service focus their wildfire response readiness on the period from April to September each year, but report that the start of the wildfire season is moving into March.

Chobham Common has experienced wildfires in April 2017, March 2019, August 2020, and January 2022, having previously been free of major fire damage for over 5 years.  There were several other wildfires on Surrey’s heathlands during 2020, including one on Brentmoor Heath in May.  So far 2022 has also seen huge fires on Ash Ranges in April and Pirbright Ranges in July.

What causes wildfires, and why are they happening so often?

Fire needs two things: ignition to start, and fuel to burn and spread.  Lightning is the only possible natural cause of wildfire in the UK and is rarely responsible as the heavy rainfall which usually accompanies UK thunderstorms makes the ground and vegetation too wet to burn.  The simple answer is that most UK wildfires are caused by people, either deliberately or accidentally.  Arson, deliberate burning of property, is often linked to fly tipping or abandoned vehicles.  Fires which are initially contained can get out of control.  Campfires and barbecues can spread or, if not completely extinguished, lead to reignited fires, which occur when fire continues to burn underground in peat and comes back to the surface.  Deliberate burning of areas of vegetation for land management purposes could also lead to fire escaping into other areas; SWT does not practise this method.  Cigarette ends can start fires if they are dropped on the ground or thrown out of vehicle windows.  Research shows that wildfires start more often at times when more people tend to visit the countryside, including weekends, school holidays and summer evenings.

Once a fire has started, the intensity and rate of spread will depend on the weather conditions and the presence of combustible material.  Dry, hot and windy weather helps fires to start and spread.  At these times, vegetation is drier, and winds can fan the flames and blow them quickly across the ground; burning material may also be blown through the air.  Climate change is increasing the frequency and severity of extreme weather conditions such as these.  Heather and Molinia caerulea (purple moor grass), common heathland ground cover plants, also contain less moisture outside the growing season, and especially when conditions have been very cold and dry.  This is thought to contribute later to a peak in wildfire occurrence and extent in the spring when more people start to visit the countryside again.

What are the problems with wildfires?

Whilst there are some parts of the world where fire can be seen as a natural aspect of ecosystem processes, naturally occurring wildfires are very rare in the UK.  Fire is dangerous for people and wildlife, both immediately and in the longer term.  Smoke inhalation and increased air pollution caused by tiny particles called PM_2.5 are hazardous to health, and during wildfire events local residents are sometimes advised to stay indoors with their doors and windows closed.  Property may be destroyed; during major fires close to residential areas evacuation of homes may be necessary, as occurred during the 2020 Chobham Common fire.

Damage to tree foliage depends on the height of the tree and intensity of the fire.  Other vegetation may be destroyed completely.  Species such as Molinia caerulea recover quickly but then tend to dominate, reducing floristic biodiversity and leading to a decline in heather, mosses and other small plants which support biodiversity on heathlands.  Rapidly mobile creatures may escape and are potentially able to return, but only if the habitat is still viable.  Smaller and less mobile creatures, including those in immobile stages of their life cycle, are unlikely to survive.  These could include eggs, recently hatched chicks, larvae and pupae.  The impact on populations and their habitats could cause local extinction, or at least long term absence, with a risk of complete extinction for species with very localised distributions.  The April 2022 Ash Ranges fire destroyed 300 hectares of habitat, almost half of the reserve.  This area will take perhaps 20 years to fully recover, leaving a much smaller area for surviving wildlife to colonise in the meantime.

Read Part 2 to find out how SWT manages heathlands for biodiversity and to reduce risk from wildfires.

By Elaine Brindley

Other blogs in this series

Wildfires: Current Heathland Management

Wildfires: Future Wildlife Management