USA — Frequent wildfire disasters in central and southern California highlight the need for fire risk reduction strategies for the region. Fuel reduction via prescribed burning is one commonly discussed option, yet there is no consensus about the effectiveness of prescribed fire in reducing the area of future wildfire.
A new statistical analysis of historic fires reveals that in central and southern California ecosystems, prescribed fires have no effect on reducing area burned by future fires. The Journal of Environmental Management paper was authored by researchers from the University of Wollongong, USGS and Conservation Biology Institute as part of the Southern California Wildfire Risk Project.
Researchers used 29 years of historical fire mapping to quantify the relationship between annual wildfire area and previous fire area in seven California counties: San Luis Obispo, Santa Barbara, Ventura, Los Angeles, Riverside, Orange and San Diego.
These data were used to measure leverage — reduction in future area burned resulting from one unit of prescribed fire treatment. For example, leverage for tropical savannas like the Serengeti is 1, where one unit of future area burned area can be directly inhibited by one unit of prescribed fire area. In Australian eucalyptus forests, the leverage is around 0.25, where 3 to 4 units of prescribed fire area is needed to inhibit subsequent fire area by 1 unit.
The leverage for central/southern California was found to be zero, which meant that no amount of area burned can inhibit future area burned. Researchers think this is for two reasons. First, southern California fires are not dependent on fuel age. The Santa Ana wind-driven extreme fires of the region will burn through vegetation of any age, and the growing acreage of easily burned, nonnative grasses also contributes to fire spread. Second, because only a random 2% of the vegetation burns each year on average, the chances of a prescribed fire patch being encountered by a fire are low. The failure was in the forest areas.Advertisement
Following a 10-year strategy, ACT fire managers have created a mosaic across the landscape of different fuel levels, burning at every opportunity.
But forests have been too wet to burn this spring and the past two summers.
A network of 500 fire trails and strategic burns along the north-west urban edge, heavy grazing and extra grass slashing will create a fortress for the territory which forecasters say faces a higher than average risk this summer.
After a fire-fuelled tornado in January 2003 killed four Canberrans and frightened thousands more, CSIRO fire expert Phil Cheney told the subsequent inquiry the fire’s penetration into urban areas under extreme conditions did not reflect a failure of fuel management on the urban interface.