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What causes wildfires?

Intense heat and bright hot flames that consume everything in their path; trees, grass, forests, houses – everything! Wildfires are an awesome and terrifying phenomenon, but what causes them, what can we do to avoid them and what is their impact on the environment?

Susie Fire in the Adobe Range west of Elko, Nevada. https://commons.m.wikimedia.org/wiki/User:Famartin

What causes wildfires?

For a fire to start there needs to be 3 things: a source of fuel, a point of ignition, and air for it to burn.

In the case of a wildfire, the air it needs to burn is all around.

The fuel is the plants on the ground itself which burn because they are dry. This can be because they grow in a dry environment such as a desert or hot, arid part of the world like parts of Africa or Australia, or it can be because a long period of hot weather and drought has meant that the undergrowth has dried out, which makes it much easier to catch fire.

The spark can come from natural and human sources. A common natural source are lightning strikes, with the white heat of the lightning spark igniting dry plants on the ground where it hits.

Charred forest following a fire in the North Cascades, Washington. Ground vegetation is just beginning to return. Originally uploaded to the English Project by Bcasterline

Human causes of wildfire include campfires, discarded cigarettes, and barbecues, though there are plenty of others. People will often want to take a disposable barbecue out into the woods or National parks during the summer for a picnic, but if there’s been a heatwave, even the slightest spark can set a fire going. Therefore many parks and forests will put up signs if there’s a fire risk banning the use of barbecues and fires and warning people to be careful not to start a fire.

Are wildfires natural?

The answer is yes and no.

In some parts of the world, wildfires have been happening for thousands of years fairly regularly and happen because the area is dry already. These fires are the ones usually started by something like a lightning strike, and in fact many of the plants that live in these regions have evolved to cope with regular wildfires.

Other areas around the world will also have endured wildfires periodically due to heatwaves and lightning strikes as above. They were, historically, rare occurrences and the new plants and trees would quickly grow to replace those lost.

However, climate change has meant that the weather patterns on Earth have shifted. Weather has become more extreme.

This means that hot periods are often now hotter and last for longer, making drought conditions more common. Rainfall happens less frequently: yes, it’s often heavier, but it doesn’t have the same effect of regularly damping down the ground and undergrowth if it doesn’t happen as often.

The Rim Fire in the Stanislaus National Forest near in California began on Aug. 17, 2013 and is under investigation. The fire has consumed approximately 149, 780 acres and is 15% contained. U.S. Forest Service photo.

Long hot periods with no rain mean more areas around the world are becoming fire-prone. All a dry area needs is a spark from a barbecue or some other source to ignite, and all of a sudden you have a massive wildfire on your hands.

In the UK, there has been an increase in wildfires in places like national parks in the Peak District, Exmoor, and in Scotland. Typically the areas that have caught fire have been grassland or heathland, with heather or gorse plants that burn quickly if they catch alight.

Firefighters have been able to bring them under control eventually, and they haven’t threatened the lives or property of any people – yet.

Wildfires in other parts of the world can be much more damaging. A wildfire through a pine forest can spread terrifyingly fast, reach temperatures hot enough to melt metal, and move across natural barriers like roads and rivers as sparks are carried in the air. The USA and Canada have seen some tragic wildlfires in recent years that have caused great loss of life.

With the shifting climate, it’s likely that these fire-starting conditions are likely to continue or even become more common, so this is something people are going to become more aware of in the future.

Nature springs back

Forest regrowth after 3 years in Hara Bog, Lahemaa National Park, Estonia

While wildfires cause a huge amount of devastation to plants, animals and the environment, in some cases they can also have a beneficial effect.

The ash fertilises the soil, and because most of the plants and trees growing in an area have been burned away, sunlight can more easily reach the ground which allows new plants to grow quickly if the conditions are right.

Even more amazingly, some plants have actually evolved to deal with wildfires, and their seeds will only germinate once scorched by flame. These are called pyrophytic plants and they have some amazing adaptions.

One of the best examples are Eucalyptus and Banksia, which grow in fires-prone Australia. The seeds are sealed in a protective, resinous casing and actually need fire to melt the resin and allow them to germinate.

What can we do to help prevent wildfires?

‘Only you can prevent forest fire’. Smokey the Bear was part of an advertising campaign by the Forest Service, United States Department of Agriculture.

There are two things we can do to help, and everyone needs to do both.

The first is to address the root cause of the fires: climate change. We all need to keep taking action to reduce our carbon emissions and decrease the amount of waste we produce to firstly stop our climate shifting any more, and secondly then help it return to historical patterns and temperatures. Sadly, this is going to take time so we still need to strictly adhere to the next point.

Secondly, it’s absolutely crucial that we prevent there being a spark that might start a wildfire if we’re in fire-prone areas during periods of drought. That means no barbecues, no campfires, no discarded cigarettes. A lump of charcoal or cigarette butt can smoulder for some time before it catches fire, so you might think it’s gone out only to find it’s still easily capable of starting a fire.

If you see signs up saying ‘no barbecues’ then adhere to them and encourage others too as well!

Finally, if you see a fire starting, inform someone as soon as possible: the smaller it is, the easier it will be to contain and put out.

Useful links

Wildfires on Wikipedia

 

 

 

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