From the Queensland Fire Department https://www.fire.qld.gov.au/prepare/bushfire/stop-bushfire-arson?

Bushfire arson is a crime, and a major threat to our community.

The devastation which can occur affects whole communities, and recovery is never quick or easy. Records show that up to 50% of all bushfires across Australia are deliberately lit, or start under suspicious circumstances. This comes at a cost of $1.6 billion to the Australian public annually.