Autumn augurs 'change to drier landscapes’

Most of Australia is at average risk of bushfire this autumn, experts say, although prolific grass growth is driving above normal potential in parts of NSW, Queensland and WA.

The National Council for Fire and Emergency Services (AFAC) says vegetation growth may dry out in the first half of this year, leading to high bushfire fuel loads in some places.

“Climate outlooks for autumn suggest a change to drier landscapes, with much of the country likely to see below average rainfall and normal-to-above-normal temperatures,” AFAC said.

“Rainfall over the last couple of seasons has created favourable growing conditions and fuels in these areas are re-accumulating quickly.”

The likelihood of reduced rainfall, high temperatures and evaporation is set to result in drier than average top-metre soil moisture by late autumn for much of Australia.

“For eastern Australia, this is a significant change from the wet soils experienced last year, suggesting the good growth associated with high moisture availability in spring 2022 may be drying out in the first half of 2023, leading to high fuel loads in some places,” AFAC’s bushfire outlook said.

The Bureau of Meteorology said today the autumn weather outlook was for warmer than average days for most of Australia except central parts of the NSW coast and eastern Victoria, and below median rainfall away from the south-east coast.

Below normal fire potential is forecast in areas across NSW, Victoria and ACT after spring and summer rainfall, though AFAC says these areas are “accumulating regrowth quickly following favourable growing conditions”.

Here is the autumn bushfire outlook by region:

NSW

Most of NSW indicates normal fire potential in autumn, though some areas are pegged for above normal fire potential this autumn due to dry grass, elevated grass fuel loads and forecast below normal rainfall.

“Even under cooler conditions, on dry windy days these areas could potentially support intense and fast spreading grass fires,” AFAC says.

Queensland

Dry conditions are likely to continue into autumn, while Northern Queensland is likely to see a continuation of the wet season.

“We are likely to see elevated fire activity continue across inland parts of southern Queensland through the early part of autumn, extending towards the coastal areas in the later part of the season,” AFAC said.

WA

Carnarvon, Gascoyne, Murchison and Yalgoo bioregions indicate above normal fire potential due to grass growth in the central western parts of WA, and warmer and drier climate conditions in the southern half of WA are forecast to persist into autumn, extending soil moisture deficiencies in the southwest region.

“Above normal fire potential is expected to persist in areas of elevated fuel loads within the Swan Coastal Plain and Jarrah Forest bioregions,” AFAC said.

Above average autumn rainfall is likely for the Kimberley and Pilbara regions, and normal fire potential is expected for northern parts of WA.

NT

Seasonal bushfire risk across the NT is expected to be normal for autumn, with soil moisture totals well above average, though any long dry spell will lift fire potential.

Victoria

A high abundance of moisture and green growth remains in gullies and on southern aspects, limiting large fire potential, though AFAC says a “return to average bushfire activity can be expected in foothill forests, especially if a dry autumn eventuates.”

Other areas are assessed as having average bushfire potential.

Tasmania

A long-term moisture deficit in areas of western Tasmania will take time to recover, so the fire potential of peat soils and moorlands may be extended and lightning strikes may ignite fires.

SA

Vigilance against fire risk will need to continue throughout autumn with ongoing slightly above average temperatures and slightly below average rainfall. As forest areas continue to dry out, and without further rain, the risk will become broader across all fuel types.

Communities face “threats from fast-moving, intense grassfires in high grass growth areas if significant fire weather returns. Recent fires, whilst they have been contained quickly, have burned at a higher intensity than expected.”

ACT

Normal fire potential for autumn is expected for grasslands, and below normal fire potential is expected for forested areas given increased fuel moisture