In a rapidly changing world under pressure from climate change we are seeing alterations in the pattern of fires, especially in places where wildfires have not been viewed as a major threat such as the UK. Fire Danger Rating Systems (FDRS) provide a measure of the threat posed by wildfires, and are informed by fuel types, weather, and fuel moisture that are used to predict the likely behaviour of wildfires. FDRS can guide how different land types are managed to reduce risk of fire and how wildfires are responded to. In this article, Dr Gareth Clay explores the increasing prevalence of wildfires in the UK and how the UK can create an FDRS which reflects our unique ecosystems.

• Fire danger is a combination of different factors, such as weather conditions and fuel type, which can affect the initiation, spread, and ease of controlling a wildfire.
• In England, between 2009/10 and 2020/21 there were around 30,000 vegetation fires each year.
• The Government and governmental agencies should collaborate with researchers to develop a new FDRS for the UK that takes into account fuels that are unique to the UK.

UK wildfires

In England alone between 2009/10 and 2020/21 there were around 30,000 vegetation fires each year. Most are less than one hectare, but larger incidents do occur, particularly in our rural regions. The mix of land types and a diverse intermingling of the urban built environment and the natural environment means there are distinct fire challenges for the UK, including threat to human life and property, as well as impacts on the natural environment, water quality, and our biodiversity.

Multiple Fire and Rescue Services across the UK declared major incidents during the most extreme period in July 2022, with London Fire Brigade declaring its busiest day since the Second World War. These sorts of events may be signals of times to come. The impact of climate change suggests we will likely see an increase in the number of days above critical ‘fire danger’ thresholds, which are set by a fire weather index to define danger, with the potential for the wildfire season to extend into autumn.

Existing systems

A number of factors can affect the risk of wildfires; for example, extended spells of hot and dry weather, and the fuel types involved. These variables impact on how fires start, how quickly they spread, and how easily a fire can be brought under control.

Fire Danger Rating Systems (FDRS) assess fuel and weather conditions to provide estimates about the potential fire behaviour under specific conditions. This information can then be used by land managers, planners, and emergency services to inform decision making.

Currently we do not have a FDRS. Instead, in England and Wales, we rely upon the Met Office Fire Severity Index (MOFSI) to help us plan for and react to fires. Unlike a FDRS, MOFSI gives an indication of fire severity based only on meteorological data and does not fully account for the varied fuel types we see across the UK. Though MOFSI can indicate if conditions are ‘worsening’ or ‘improving,’ its primary role is to determine if open access land should be closed to prevent the spread of fire. However, MOFSI does not always work effectively. For example, during the dry summer of 2018, in some regions the indices did not rise sufficiently to trigger land closures in areas that went on to experience severe wildfire. This insensitivity demonstrates that other tools are required to properly forewarn responders, landowners, and government agencies about likely fire behaviour.

However, we can learn from the USA, Canada, and Australia, who have been developing their FDRS for decades, using remote sensing technology and localised data on fuel types. The specific thresholds at which different UK landscapes pose a fire risk during very dry weather conditions remains unknown. However, using the latest research the UK can develop a strategy which better reflects our varied vegetation, landscape, and climate.

 Building a UKFDRS

The main source of fuel for a wildfire is vegetation. However, we have limited research specific to key UK fuels like heather, gorse, and grasses. Researchers at The University of Manchester, in partnership with other universities in the UK, are leading a major project to develop new insights into the location and condition of our important fuels: seeing how they react to different weather conditions throughout the year and quantifying how flammable these fuel types are, which will ultimately allow for a tailored UK fire behaviour model to be produced.

Early analysis of field data from the project from monitoring sites across the UK suggests that there are key periods of the year when fuel moisture and flammability metrics are markedly different – for example, heather in the winter/early spring months has a lower fuel moisture and higher energy release compared to summer months where, following the greening up of vegetation, it has a higher fuel moisture and a lower energy release.

In normal conditions these seasonal plant cycles may limit the occurrence and nature of fires in the summer in many fuel types. However, extreme weather, as we saw in 2022, can push the fuels in summer to levels of flammability normally seen in spring and, combined with more severe fire weather (like, high temperatures and low humidity), can lead to catastrophic fires. By quantifying these seasonal and vegetation differences for the first time, we can better model fire behaviour during different seasons.

Next Steps

The next step in this journey will be to take the findings from our research and work with partners to develop an operational FDRS in the coming years. These partners include government departments, like the Home Office, Cabinet Office, and Department for Environment, Food and Rural Affairs; the Met Office; wildfire forums across the UK; and landowners and managers.

This system would allow for management decisions to be taken in advance of heightened fire conditions, such as stepping up additional Fire and Rescue Service crews, modifying land management practices when the danger is high (for example, the cessation of managed burning or avoiding using spark producing machinery), or increased public-facing messages, including warning signs at popular recreation spots. Many of these already happen at a local level and within organisations, but through sharing good practices we will be able to connect these to outputs from a FDRS.

Wildfires require a holistic response from stakeholders across government departments, devolved administrations, and different sectors. A future FDRS for the UK will need to take this into account and acknowledge the varying regional and sectoral needs. Who ultimately co-ordinates a future system is not yet clear, however leadership from government is required. Developing a functional system for a range of users will take time, just look at the USA, Canada, or Australia where their work has been going on for decades. However, by working together across sectors, projects, and disciplines we can introduce a UK FDRS that has a significant impact in the years to come.