Bushfires: Definition, Causes & Effects

Instructor: Artem Cheprasov
Bushfires are devastating wildfires that can wreak havoc on nature, economies, and people. This lesson defines bushfires, explains how they can start, and goes over what effects they may have.

What Is A Bushfire?

Those from the Western part of North America are probably familiar with the concept of a wildfire, a large fire that spreads very quickly and is difficult to place under control. Usually this type of wildfire spreads through the forests of North America.

One type of wildfire is known as a bushfire, an uncontrolled fire that burns through scrubland, which is common to Australia (and many places in Africa). Like all wildfires, a bushfire places nature and man under threat. Let's find out more about bushfires in this lesson.


There are many factors that lead to a bushfire or influence its spread. This includes the type of fuel in question. Some grasses as well as twigs can burn very quickly. On the other hand, large tree trunks don't burn as easily.

The moisture of the fuel is another critical factor. Fuel that's wet is unlikely to burn. Similarly, increased humidity decreases the chances that a bushfire will start. On the flipside, lower humidity, higher temperature, and drier conditions all help ignite and spread a fire.

Wind plays a key part in the spread of bushfires too. You've heard of 'fanning the flames'. Well, wind provides much needed oxygen for a fire. Like you need oxygen to live, so does fire. Wind also spreads the fire around more rapidly.

And what do you think? Do you think a bushfire will:

A. spread uphill faster?

B. spread downhill faster?

C. spread uphill and downhill equally fast?

The answer is A. A bushfire will spread up a hill much faster than it will down a hill thanks to the processes of convection and radiation. These processes pre-heat higher ground much better than lower ground and so the fire spreads upwards faster as a result. Think of the Australian landscape - hot, dry, and with large expanses of grasslands, and you can see why bushfires might be common.

But what actually starts the fire? Well, there are many possibilities. Some are natural. For example, lightning can provide the spark that sets off the blaze. It's estimated that natural sources of ignition account for about 50% of Australia's bushfires. You may have guessed the cause of the other 50%.

Unfortunately, it's people. Sometimes, the cause is accidental or as a result of neglect. For instance, someone may have forgotten to properly put out a campfire. Other times, it's arson, or the purposeful burning down of property. This is different than creating controlled fires, which is a form of land management to help prevent catastrophic bushfires.


Either way, the effects of a bushfire can be devastating. Large areas of land and nature are destroyed. Wild animals and people are killed, homes are burned down. Livestock and agricultural land is threatened or destroyed.

The amount of smoke that enters the air can exacerbate or cause respiratory problems. For instance, people with asthma or bronchitis may experience a worsening of their signs and symptoms as a result of all the smoke in the air.

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