The Yukon gets its fair share of electrical recharging in the summer. On average about 15,000 bolts of lightning hit the territory every year, with most of those strikes occurring in July.

These random bolts of electricity have a big impact on the territory. While humans cause most of the Yukon's fires, it is the fires started by lightning that burn the most area.

On average lightning causes about half of the territory's fires, but accounts for 95 percent of the total area burned. These fires usually ignite in remote areas far from fire fighters and their equipment, and often lighting will strike more than once in the same area, so firefighters have more than one blaze with which to deal.

In contrast, fires set by humans usually occur close to communities where they are detected early and put out quickly. Almost 80 percent of the human-caused fires occur in and around Whitehorse, where resources are close at hand.

Fires sparked by lightning can quickly turn into raging crown fires that are virtually impossible to control. That's because in our part of the world they are usually striking a forest that is more than ready to burn. Of the different forest types found in North America, the boreal forest is the most flammable of them all.

Black spruce, loaded with sap, are a particular fire hazard. The lichens on their low hanging branches provide a convenient ladder for fire, allowing flames to climb quickly up the small spindly trees into the canopy.

The person responsible for managing fires in the territory says it is remarkable how lightning seems to zero in on the trees most ready to burn.

"It's like fire has radar for mature, late-succession coniferous forest. The older it gets, the more flammable it becomes," says Al Beaver, the fire-management planning supervisor with the Department of Indian Affairs and Northern Development.

But Beaver also points out how fires are an essential part of life in the boreal forest, occurring about every 50 years in areas such as the central Yukon.

Without fire, organic matter continues to accumulate on the forest floor, locking up valuable nutrients and keeping soil temperatures cold. Without fire, forests of black spruce could eventually turn into treeless bogs.

"Fire is the great reaper, sanitizer and decomposer, opening up old growth stands and making way for new generations of trees," he says.

Fire rarely spreads evenly through the forest, so it maintains a mosaic of vegetation. This patchwork of species of different types and ages is important for wildlife as it creates diverse habitats.

"The health of the boreal forest depends upon fires. The great variety and abundance of plant and animal life in the Yukon is because of fire, not in spite of it."

Most of the fires set by lightning occur along the Tintina Trench, the rift valley that runs diagonally across the Yukon. A network of lightning detectors provides locations for strikes, and has detected an interesting pattern.

In May most of the strikes occur along the trench just south of Dawson City. During June and July the area with the most strikes shifts gradually southeast towards Whitehorse, but then retreats back towards Dawson in August.

Not every strike in this lightning alley results in a major fire. Sometimes the rain that accompanies the lightning storm will put out small blazes.

But Beaver says that when the fire danger is high, fire crews often never have a chance to control fires set by lightning. "In dry years, by the time the fire crew gets there, they just see a great big billowing cloud of smoke."

The huge blazes set off by lightning can present a major challenge for people like Beaver. Between 1985 and 1998, 79 percent of the fires set by lightning were brought under control, while the success rate with fires caused by humans was 97 percent.

In 2001 the DIAND Fire Management Program completed a major analysis of the fire regime in the Yukon, and its ability to fight different types of fires. This analysis will be used for a series of public consultations on fire and land management, and next week's column will cover some of the issues involved.

For more information on fire management in the Yukon, contact Erin Hockin at 667-3312.