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What were you doing on 19 July 2022? If you need any help to jog your memory, it was the hottest day in modern British history when temperatures in the capital broke 40 degrees Celsius for the first time on record.
I hope, therefore, that the answer is ‘somewhere with air conditioning’ or failing that ‘at home and following recognised practice for keeping a home cool’.
But if you were a member of the London Fire Brigade (LFB) (and I know from the subscriber data that there are handful reading this blog), then the answer would be ‘extremely bloody busy’. Busier, in fact, than on any day since World War II.
The Brigade was called to dozens of fires throughout the day. Domestic gardens, shrubs, parks, residential and commercial buildings – the LFB was pulled to all sides of the capital. The most serious incident, in Wennington, a village just inside the London/Essex border, saw a devastating fire spread from a backgarden to grassland and then back into neighbouring properties, resulting in damage to 37 buildings, some of which were gutted. In total, the Brigade received 2,600 calls about more than a dozen fires burning simultaneously in different parts of the city.
Those planning for the hotter future of the UK should take this day as a stress test. No one knows quite where climate change will end up, but under any model we are currently at the coolest we will be. Things will only get hotter, which means London will face many more days similar to 19 July 2022.
This calls for us to take the threat of urban wildfires in the capital (and other major UK cities – although London, as the hottest in the UK, is the most exposed).
London sits in a dangerous twilight zone for wildfire. Because it has not historically been hot enough for wildfires to be a particularly prevalent risk, it is not very well adapted to it.
Our fire service is mostly equipped and trained for residential and commercial fires, car crashes and other common urban incidents. While that is changing, progress in the under-resourced, over-stretched public sector is rarely fast.
And it is not just about firefighters. The general population do not yet sufficiently appreciate the risk of starting a BBQ on dried out yellow grass. And our vegetation is highly vulnerable to fire, and in close proximity to residential properties.
Stroll through Epping Forest, for example, and you come regularly to houses whose gardens back straight on to the forest, with no natural fire breaks at all. The cottages in Wennington were connected directly to the grasslands and completely defenceless when they ignited.
In fact, one of the best things about London (its beautiful and wild green spaces) will become an achilles heel as we move into the 20th Century – offering, as they do, fuel which is not present in other hotter cities around the world and often located in dangerously close proximity to highly developed urban areas. Wanstead Flats for example – a huge grassland in east London – has burned several times in the 2010s and 2020s, with its boundaries touching the densely populated streets of Newham, Waltham Forest and Redbridge.
In recent years, excellent initiatives around bio-diversity have encouraged local authorities to stop mowing verges and to transform grassy areas into meadows by planting wildflowers and encoraging them to grow wild. This is great for biodiversity but is yet another area where climate change mitigations seem to have a corresponding price in fire safety – these re-wilded verges will be tinder when dried out by a prolonged heatwave.
I get chills now, when I run down the Greenway (known as the Sewer Bank to true locals) near my home in Newham, and look at the dense, long grass and flowers, scrambling down the verge and right up to the wooden fences of the terrace houses, starting to yellow and dry in the sun.
Research recently published by Imperial College London academics Guillermo Rein and Jamie John has looked in depth at this growing risk and turned up a trend which should give us both cause for concern and an opportunity to prepare.
The report looked at LFB data on wildfires – both the number of incidents and the length of time fire engines were deployed to fight them, meaning they were assessing both frequency and severity. Days which were major outliers in this dataset were branded ‘firewaves.’ The report found five such incidents since 2009: one in 2018, and four within a single year, in 2022.
But what was driving them was not simply temperature. There have been heatwaves in London with sustained high temperature and no firewaves. Instead, the academics looked at ‘vapour pressure deficit’ (VPD) data – which is a measure of the atmospheres ability to extract moisture from the land surface. Essentially it is the process which dries the vegetation into fuel.
Here, the correlation was rock-solid. As VPD rises, so do wildfires. In fact, their research suggests (albeit with the cavaet of a limited sample size) that 10 consecutive days of VPD above the 80th percentile will be a very strong indicator of a coming firewave.
So this gives us a chance at early warning. If VPD data is being monitored and recorded we can do what we need to do to limit the risk: warn those living close to grassland to be alert, send out major public health warnings about the risks of BBQs on dried grass (even domestic gardens), gear up the LFB (possibly even with a volunteer stand-by force similar to European countries which face regular wildfires).
But what it also tells us is that more fire is coming. The five firewaves have all been within the last six years. VPD figures will continue to rise during the hot, dry summers the next century will bring.
And if one coincides with high winds which drive the embers of the fire forward, starting fires which can leap the natural barriers of roads, batter their way through windows to burn domestic homes and ignite cars and tear through the city faster than firefighters can respond… then, well London has seen the consequences of that sort of fire once before and if you want to read more about it I recommend the diary of Samuel Pepys.
Firewaves are just one of the ways in which our worlds will become more dangerous in the coming century. It is time to take our heads out of the sand and start preparing for some of those risks. And in London that means realising that it is becoming a wildfire city and preparing as best we can for that future.
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For more on this topic, read Catherine Levin’s interview with Professor Guillermo Rein which originally appeared in the August 2023 print issue of Emergency Services Times.
