WITH GRASS and undergrowth tinder-dry after the hot weather, fire is a hazard to forestry.Hundreds of acres of woodland are destroyed every year, often through carelessness on the part of campers or picnickers. But fire is also used as a management tool, not least in the American national parks, where blazes started by lightning strikes are often left to run their course. In stands of giant redwoods, for instance, a fast- moving fire burns away the litter of dead branches on the forest floor without harming the mature trees, which are protected by their bark. With the ground cleared and light let in, falling seeds can germinate.
On grouse moors in northern England and Scotland gamekeepers regenerate the heather by burning off strips of old growth in early spring. Their aim is to produce a mosaic of patches with different ages: young shoots for the birds to feed on; longer plants to give them cover. The operation needs to be controlled, because the fire can easily go down into the roots of the heather, which contains inflammable oil, and travel considerable distances underground, before bursting into life elsewhere.