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Global Boiling: Australia’s Black Saturday Of Extreme Fire

By Guest Contributor on March 1, 2009 at 9:31 pm

"Global Boiling: Australia’s Black Saturday Of Extreme Fire"

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Our guest blogger is Erica Newman, research associate at the College of Natural Resources and Center for Fire Research and Outreach at the University of California, Berkeley.

Firetruck fleeing the bushfire.Even in Australia, where people have learned to live with large wildfires, February’s “Black Saturday” fires in Victoria blew away all expectations. Of the hundreds that died, those who stayed had no time to prepare, and many who fled were overtaken by the fast-spreading flames and died in their cars. Multiple days of above 100-degree Fahrenheit temperatures, extremely low relative humidity and 100 mile per hour winds resulted in an unstoppable spread of the flames, 100-200 foot flame lengths, and fire intensity unlike anything ever before recorded anywhere on the planet.

Wildfire expert Max Moritz, a professor at the College of Natural Resources and Center for Fire Research and Outreach at the University of California, Berkeley, explains these extreme conditions raise new questions:

Although we won’t know many of the details until an assessment of the recent Australian fires is completed, the weather conditions and rates of fire spread we’re hearing about are extreme. It highlights a special case for both agencies and homeowners, and we have a lot to learn from each other about what does and does not work under weather conditions that are this bad.

So what caused this colossal inferno? In pointing to arson as the cause of these fires, we miss the overall significance of the fire dynamics that gave rise to this event. While arson is a lamentable and criminal source of ignition, with relative humidity and fuel moisture at below four percent, a lit cigarette or a spark thrown off by a moving vehicle could have caused similar wildland fires. Where there are people, there are always sources of ignition — what fire scientists call the “human-ignition component.” The larger issue at stake here is what gave rise to such extreme fire weather.

Australian fire scientists say that this area of Victoria has experienced between five and 30 years of drought (depending on if you are counting by successive years or overall water balances), the worst in perhaps 1000 years. Some, perhaps rightly, blame global climate change for what is known as the “Big Dry.” Diminishing rainfall, increased temperatures, and increased atmospheric instability all lead to higher fire danger.

An open question for scientists is whether or not with global climate change, we are experiencing “novel ecosystems” with entirely new combinations of environmental conditions. Is Australia really experiencing a “drought,” which is less-than-normal rainfall, or is there a new normal? Should Australia listen to its firefighters and be preparing for a permanently drier future with much more intense fire dynamics?

Australia has a history of successful fire management. Because of the inevitability of fire in Australia’s fire-evolved ecosystems, people have learned to expect and prepare for fires in a highly efficient, centralized manner. The “Prepare, Stay and Defend, or Leave Early” policies have long protected the lives of both citizens and firefighters, and reduced damage to homes and other buildings.

In a paper out this week in Environmental Research Letters, four Australian scientists and three scientists from California including Moritz, examine the policies and recommendations that both countries have in place for dealing with wildland fire on the urban interface.

In the “prepare, stay and defend” approach, property-owners are educated in fire suppression, such as putting out spot-fires, having buckets of water on hand, filling house gutters with water, creating a “defensible space,” and so on. People who chose to stay with their homes are also encouraged to keep protective Nomex clothing and firefighting implements on hand. Those who follow the “leave early” strategy do so when fire is reported for their area to give the wildfire a wide berth.

The unusual combination of extreme fire weather and the sudden onset of fire created conditions in which neither strategy worked. Leaving early works only if there is time to send out a warning. Those who would “prepare, stay, and defend” would have been reducing fuel loads in their yards well before this event, but it is unclear whether landscape-scale fuel treatments or even lowering fuel loads in the immediate vicinity of structures lowers fire hazard in wind-driven events, such as this one.

It will be up to Australian fire scientists and policy analysts to decide if their fire strategies need review. It the face of so primal a force as fire and on this scale, fighting the fires themselves is impossible, but perhaps one solution–fighting global climate change–is not.

Update

The state of Victoria has “declared a total ban on open fires tomorrow as high temperatures and strong winds are forecast to return this week.”

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