Fort McMurray's horrifying experience shows humans can't stand in nature's way: Don Pittis

DonPittiswas a forest fire fighter for nearly a decade,and studiedforestry atLakeheadUniversitybefore switching to economics and journalism.

In nearly a decade of being paid to fight forest fires, I rarely experienced the intensity of the fire thatthe people of FortMcMurraywitnessed this week. And while I have felt in terror for my life, I have certainly never seen such economic destruction.

It's not because such giant conflagrations are so rare. It's because firefighters only get that close to the roaring, movinghead of a large forest fire when things have gone badly wrong. Canada hasthousands of fires every year, but the giant ones seldom come close to communities as big as FortMcMurray.

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The leading edge of a crowningfire is always terrifying. The noise is often compared to a passing freight train, but unlike a freight train, the firecannot be stopped.

Understanding the power of a moving forest fire isn't hard once you think of the process at work.

Firestorm effect

Just like a camp bonfire, the heat of the flamespushes the air into a convection column. When there is little wind, the fire burns straight up, not sideways, creeping slowly through the brush, occasionally flaring up throughthe needles of aconifer with a bright yellow roar, something called candling. In the absence of firefighters, the fire moves forward gradually, finding new fuel along its edge as the fuel behind the edge smolders to ash.

But powerful winds like those in FortMcMurraycan bendthe convection columnforward so it passes through the crowns of the trees just ahead of the fire front. Instead of candling individually, the fire leaps through the needledcrowns evenbefore the fuelbehind hasfinished burning. Then the process is repeated.

Instead of just a thin leading edge of the fire gradually spreading, a wide swath of forest burns at once, flaring up into the sky, throwing up bark, branches, even whole trees.

Firefighters standing in front of the blaze would suffocate as the fire consumesthe oxygen and replaces it with smoke. That's why, despite economic damage, they must be pulled out.Water bombers have almostno effect.

Sometimes called a firestorm, such an intense infernocan spread faster still as embers are sent up and then pitched forward by the upper winds. The radiant heat the reason you have to move back from the campfire when toasting a marshmallow is so powerful it can ignite trees across a river,road or firebreak.

Backfiring

As witnesses in FortMcMurrayhave described, it's the radiant heat that can causepassing vehicles to burst into flames and makes people inside cars feel intenseheat despite air conditioning.

Giant fires create their own weather, sucking air along the ground infront of them to feed the convection column. The one way sometimes tried tostop or slow a giant fire is to light another fire in front of it, taking advantage of the surface wind sucked toward the main fire. The intent is to rob the main fire of fuel.

An attempt to use thetechnique, sometimes called a backfire, was the time I most feared for my life as a forest fire fighter. The trouble is backfires can sometimes backfire, as a shift in wind turns the burnout fire into the new leading edge. We made a run for it between walls of flame, holding hose bags and helmets to shield our faces from theradiant heat.

There is no doubt this is an early beginning to the fire season. Provincial fire crews don't usually gear up until the beginning of May.

Spring fires are special

And spring fires are strange things. Despitehot conditions up on the surface,the ground and deep roots can remainfrozen, meaning the trees are not yet flush with water. In spring fires even deciduous trees, normally a partial firebreak, can flare up in eerie yellow smoke.

There is no question that firefighters did what they could. Despite images of the sooty firefighter saving Bambi, human life including that of the firefightersranks as the top firefighting priority, followed by human property and the commercial value of the trees. Animals must fend for themselves.

The good thing about forest fires is they come and go quickly. Just as when you stop adding fuel to acampfire, following the intense leading wall of flame, the interior of a forestis nothing but smoldering ash. You can walk through it in good boots.

The Fort Mac fire may burn on, but the chances of a fire circling around through unburned fuel and taking another pass at the community are tiny. As Canadians pull together to help the people of FortMcMurray, they can only stand in awe, as firefighters do,of the power of nature.

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More analysisby Don Pittis