Bushfires in Australia are mainly caused by a mix of natural ignition (especially lightning), human activity (both accidental and deliberate), and weather and landscape conditions that make fires easy to start and hard to stop.

Natural and human ignition

Both nature and people play a major role in how bushfires start.

  • Lightning strikes are a major natural cause, especially in remote bush and grassland areas.
  • Human causes include dropped cigarettes, escaped campfires, machinery that throws sparks, powerlines, and other accidents.
  • A significant share of fires are deliberately lit (arson) or considered suspicious by investigators.

Weather and climate conditions

Australiaā€™s generally hot, dry climate makes it one of the most fireā€‘prone places on Earth.

  • ā€œFire weatherā€ ā€“ high temperatures, low humidity and strong winds ā€“ makes it much easier for a small flame to become a fastā€‘moving bushfire.
  • Drought and recordā€‘low rainfall dry out vegetation and soils, creating more flammable fuel and more intense fires.
  • Climate change is increasing heat extremes and lengthening the fire season, contributing to more frequent and severe bushfire conditions.

Fuel: what actually burns

Bushfires depend on the amount and type of fuel available.

  • Leaves, bark, dead branches, shrubs, grasses and trees all act as fuel; dry material ignites more easily and burns hotter than moist fuel.
  • Periods of good rainfall can actually increase risk later by boosting plant growth, which then dries and becomes extra fuel in a hot summer.
  • Heavy fuel loads and longā€‘unburnt vegetation help fires burn more intensely and over larger areas.

Landscape and spread

Once a bushfire starts, the landscape and weather shape how it spreads.

  • Steep slopes allow fires to race uphill quickly because flames can preā€‘heat the vegetation above.
  • Strong winds push flames and embers ahead of the main fire front, starting spot fires kilometres away.
  • Close proximity of towns and houses to bushland adds buildings and other materials to the fuel mix, increasing damage risk.

Why recent bushfires have been so bad

Recent seasons, including the 2019ā€“20 ā€œBlack Summer,ā€ have been severe because several risk factors lined up at once.

  • Record heat, very low rainfall and widespread drought dried out forests and grasslands across large areas.
  • Increased fuel loads, combined with strong winds and ignition from lightning and human activity, allowed fires to grow rapidly and become harder to control.
  • Experts note that while individual fires can start from many different triggers, the underlying buildā€‘up of dry fuel and hotter, drier conditions are key reasons large, destructive bushfires are becoming more common.

Information gathered from public forums or data available on the internet and portrayed here.