How do bushfires happen?

Like making dinner, bushfires require some key ingredients. These are: (1) fuel, (2) fuel dryness, (3) ignitions and (4) fire weather.

Fuel means plants that can be burned. This includes grasses and shrubs, leaf litter and twigs, tree trunks, and really any other plant material.

For fires to occur, the fuel must be dry enough to catch on fire. If the plant material is still growing and therefore has water inside of it, it is more difficult for it to catch on fire. Likewise, if the fuel is moist because it has recently rained, then it is unlikely to catch on fire. This is one of the reasons bushfires are more common during summer, when it is warmer and dryer.

For a fire to occur, there also needs to be an ignition source. Ignitions are often accidentally caused by humans. For example, there have been ignitions caused by a people driving over a dry paddock and their hot exhaust pipe ignited long dry grass. There have also been examples when people failed to put out their camp fire. These human-caused ignitions are something that we humans have control over, and thankfully we seem to be getting better at managing them. There are also natural sources of ignitions, like dry lighting, which is lightning that occurs when it is not raining. Dry lightning unfortunately seems to be getting more common.

The final key ingredient of a bushfire is fire weather. Fire weather describes the type of weather that would cause a bushfire to start spreading. Bad fire weather consists of hot, dry, and windy weather occurring at the same time. When it is hot and windy, the fire can quickly go from a small fire to a raging bushfire. These are the days when fire bans are in full effect, which is why it’s so important for us to make sure we don’t provide any new ignitions on days when fires can spread easily.