Inappropriate fire regimes

The Australian bush has adapted to fire over millions of years. Prior to the arrival of indigenous people to the continent, bushfires often started from lightning strikes. Once aboriginal people started to arrive approximately 50, 000 years ago, they used fire (fire-stick farming or mosaic burning) to help manage the vegetation by changing the structure and composition, and also as a hunting aid by flushing out animals. This changed many ecosystems, with the result of plants and animal species becoming adapted to fire or even disappearing from the landscape altogether. Many of those that have become adapted to fire have developed physical characteristics to assist them in survival during and after a fire event. In some cases plant species have become reliant on fire to regenerate or to release their seeds. Other plants benefit from the increase in light, reduction in direct competition and influx of nutrients in the soils. As with plants, some animal species benefit from their habitat burning, whilst others are disadvantaged. Some are either killed, whist others have the ability to escape. Overall fire can have both positive and negative effects on an ecosystem.

Fire ‘regimes’ have changed substantially since pre-European settlement and are now limited to either ‘uncontrolled’ bushfires, or ‘controlled’ or ‘prescribed’ burning . This has resulted in many plant and animal species being adversely impacted due to fire being either too often, too infrequent or too severe. The potential impacts of these scenarios are outlined below.

Wildfires

  • Catastrophic loss of biodiversity (Loss of habitat and significant populations of plants and animals);
  • Changes in plant species composition and structure due to loss of fire-sensitive plant species;
  • Too severe fires can lead to elimination of plant populations, even those that possess some adaptations to fire;
  • Increased weed invasion following fire;
  • Loss of hollows in large trees (however fire also can also enhance hollow development in some instances);
  • Reduction in invertebrate numbers and diversity.

Too frequent burning

  • Disruption of life cycles of plants and animals, and has the potential to prevent plants and animals from recolonising the area;
  • Changes in plant species composition and structure due to loss of fire-sensitive plant species;
  • Increase in nutrient levels which aid weed growth
  • Increase in weed invasion;
  • Reduction in the capacity for native plants to germinate through increased competition with weeds, thereby increasing the fire risk;
  • Prevention and reduction of native seed set in soils;
  • Loss of woody debris and leaf litter which provides habitat and enhances soil health and protection from erosion;

Ill-timed prescribed burning

  • Can threaten plant populations by damaging those flowering/seeding or sensitive juvenile plants;
  • Can threaten fauna population during optimal breeding times.

Too in-frequent burning:

  • Changes in plant species composition and structure due to loss of those plant species that may rely on a fire event to regenerate;
  • Reduction in optimal habitat for some species