As blazes spread across Corfu, Rhodes and Albania, many have been shocked at how quickly the fires have spread – and it is easy to get caught out.
The average fire travels at around 14mph, but, as Professor Nigel Arnell explains, the top speed is much higher.
‘You can’t put a number on it, but we’ve heard stories from California and other places where fires are moving faster than speeding vehicles,’ he said. ‘They can be very, very fast.
‘You wouldn’t be able to outrun it.’
The speed of the fire depends on two factors – the amount of dry material to fuel it, and the weather conditions.
‘What you really need is lots and lots of dry material,’ said Professor Arnell, a professor of climate system science at the University of Reading. ‘For that you need a prolonged dry period, and that will mean all the undergrowth is dry.
‘What sustains it is all the material – and also how windy it is.’
Wind speed has a direct correlation with how quickly a fire spreads.
‘It’s the wind that influences the rate of spread, and also determines how difficult they are to keep under control,’ said Professor Arnell.
‘What you typically find is that the worst fires are after long dry conditions in windy periods, so if it’s windy for a long time, then the fire is going to spread really quite quickly – especially if there is lots of dry material around.’
In Britain, wildfires remain fairly rare. When they do occur however, they are usually very different to those seen in Greece, the US and Australia.
‘In the UK we definitely underestimate how quickly fire moves,’ said Professor Parnell. ‘Our wildfires are typically on heathland and they’re slower moving. There’s no high top vegetation so it doesn’t move particularly quickly.’
In forest fires, the flames travel quickly across treetops, speeding up the spread.
There is a third element needed for wildfires to proliferate alongside dry vegetation and wind – the spark. This can occur naturally, such as from a lightning strike, or may be a result of human activity – but isn’t always deliberate.
‘It’s usually unintentional,’ said Professor Arnell. ‘The discarded cigarette, disposable barbeque, or even a bottle left on the ground that reflects the sunlight and causes the ground around it to heat up.
Fire has long been used as a method of land management, but as droughts and heatwaves increase in frequency and intensity due to climate change, the risk of wildfires – whatever the spark – is also growing.
The UN Environment Programme has warned that climate change and wildfires are ‘mutually exacerbating’, and expects the number of extreme fires to increase 14% by 2030 – and 30% by 2050.
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