How Do Bushfires Start and Spread?

Recently, there have been many bushfires across the country. The soaring temperatures and lack of rain aren’t helping the situation, and many brave firefighters are battling the flames, trying to get them under control.

It can be a scary time, particularly if you live close to where a fire is burning, or have loved ones in the vicinity of uncontrolled flames.

In this article, we attempt to answer the questions: how do bushfires start, and how do bushfires spread?

Fire burning near a forest

What starts a bushfire?

There are many different elements that can cause or contribute to the start of a bushfire. Some examples of causes are listed below.

Land burn off

Many people (particularly those on properties) participate in burn offs, to help new plants grow. Backburning can also be done to burn off vegetation during the cooler months to help prevent fires from spreading during the warmer times. It is important for burn offs to be regulated and to ensure the law is followed when participating in the practice. When burn offs occur at a particularly poor time, there is a chance they can get out of hand and cause an uncontrolled bushfire. Across many places in Australia, burning off is banned during Fire Danger Periods, and it is a must that you check with your local council for any restrictions before burning off.

Bushfires and arson

Sadly, there are some people who choose to deliberately start fires. In each Australian state/territory, arson is considered a serious offence, which can have heavy penalties for people convicted of the crime. Fires can lead to the loss of property and life, and as such, the deliberate starting of fires is a serious matter.

Cigarettes

Embers from cigarettes can cause fires, particularly on hot and dry days. It is important to not smoke around areas that are dry and susceptible to fires and to always ensure cigarette butts are disposed of correctly and responsibly.

Lightning

This is the most common cause of fires in areas that are remote. Dry storms (those without rain) are bad news for rural areas that have already been experiencing dry conditions. Lighting striking dry vegetation can be a recipe for the start of a fire. When these storms are combined with strong winds, it makes a bad combination for our country. This is one way that bushfires start naturally in Australia.

How do bushfires spread?

Many different elements can contribute to bushfire behaviour (fire spread and speed). These include:

Weather and wind effects on bushfires

Water beats fire, and wet conditions can help to stifle a fire’s journey. Dry conditions can keep a fire burning, and high winds can cause embers to spread across large areas. Did you know that a fire’s embers can travel as much as 40 kilometres ahead of the fire itself? Combine this travel distance with hot, dry weather, and fires can spread quickly.

How does slope affect bushfire spread?

When travelling uphill, fires will burn faster, which also increases the intensity of the fire. As a general rule, a fire will double its speed for a 10-degree increase in slope. A 10-degree decrease in slope will generally slow the fire by half.

Dry vegetation and bushfires

Dry vegetation catches fire easier than non-dry vegetation. This means at times when there has been a lack of rain and hot days that dry out the land, fires can find it easier to travel and spread. Planting fire retardant plants can help protect from the dangers of fire.


The fires burning across our country are devastating. We are fortunate to have the efforts of firefighters (both volunteer and not) helping to control the flames. With our increasingly warm and dry weather, it is important to learn as much as we can about what causes fires to start and what causes them to spread.

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