Tathra losses unlikely to have been worsened by lack of planned burns
"Despite these activities, the fire at the weekend was intense and burnt through these areas," it said. "The fire was wind-driven and blew embers well ahead of the main fire front."
Professor Bradstock said multiple studies – particularly since the devastating Black Saturday bushfires in Victoria in 2009 – had shown broadscale planned burns were less effective in suppressing fire activity than work much closer to homes and other buildings.
Creating a so-called "defensible space", extending about 40 metres from residences, was critical, he said. Depending on the area, further work out to a couple of kilometres would also help.
Hazard-reduction burning thinking has evolved. Victoria, for instance, has shifted from setting annual quotas of areas to be burned to a more risk-based approach targeting specific areas of concern, as used in NSW.
Climate change has also seen a reduction in cool-season rainfall in both south-west and south-east Australia, two regions that are naturally bushfire-prone.
In addition to an increase in the number of days with high fire danger, the bushfire season has extended outside summer months, particularly into spring, researchers have said.
One side-effect is the available opportunity to conduct fire reduction is shrinking, resulting in the need to concentrate burning activities. These often happen on weekends, when volunteers are more likely to be free.
Those busy periods then draw public complaints about air pollution because the same conditions that make such burning relatively low risk – such as dry, still days – also allow smoke to settle over nearby populated regions including the Sydney basin.
Ecologists also raise concerns about the impact of hazard-reduction burns, particularly if done too often, can have on key habitat.
Large trees that are home to many marsupials, birds and lizards, are often susceptible to flames that can penetrate cracks or holes in trunks, and destroy them from within.
Professor Bradstock said early evidence suggested that embers carried by the high winds travelled some distance before settling on Tathra homes and igniting them.
He noted that several clusters of properties were destroyed, indicating house-to-house propagation.
The increasing tendency to pack in houses almost fence-to-fence on the outskirts of town and cities in areas known to have fires could mean "we are setting ourselves up" for such propagation events, he said.
Sunday's forest fire danger index was about 55 for the NSW south coast. While possibly the highest for this late in the season, it was a record for March, the Bureau of Meteorology said.
Peter Hannam is Environment Editor at The Sydney Morning Herald. He covers broad environmental issues ranging from climate change to renewable energy for Fairfax Media.
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