How they fight a bushland inferno
Trees explode into an inferno; balls of fire leap from tree top to tree top; the wind whips inwards to refuel the holocaust of fire and smoke. Close up, a forest fire is a terrifying spectacle.
But it is a scene repeated thousands of times a year in temperate forests around the world, most dramatically in the wilderness areas of California and the bushlands of southern Australia. These – as well as the scrubby maquis of the French Mediterranean and the evergreen fynbos of South Africa – fall easy prey to a dropped match, sunlight amplified through a discarded bottle, or a lightning-bolt. In Australia, the heat of a fire can vaporise eucalyptus oil, igniting whole trees in gaseous explosions.
The destruction can be massive. In 1949, France lost 385,000 acres of forest (156,000 hectares) in 350 fires. In 1971, fires in Wisconsin and Michigan burned 4.2 million acres (1,700,000 hectares) and killed 1500 people. In 1985, across the United States, 81,662 fires burned almost 3 million acres (1,200,000 hectares).
Flames can spread through tinder-dry bush at speeds of over 90mph (144km/h). Occasionally the combustion causes a fire whirlwind, a chimney of hot air supplied by inrushing winds that can uproot trees and shoot them into the air, starting new fires hundreds of yards away. To combat such destruction, major organisations like the US National Forest Service and Australia’s State Bushfire Control Authorities assemble formidable forces. In Australia, most firefighters are volunteers.
In September 1987, when fires burned over a huge region in California, Oregon and Idaho, one night of firefighting in just one area – Stanislaus National Forest involved 376 fire engines and water tankers, 94 bulldozers, 16 helicopters, 13 air tankers and 4500 firefighters.
Perhaps the greatest defensive weapon against forest fires is information.
Satellites, night-flying planes with infrared cameras, and computer coordination all allow fire conditions to be forecast and fires monitored when they break out. To combat a blaze, firefighters use a combination of two main strategies: cooling and containment.
Dousing a fire with water not only cools it: in large quantities it also breaks up burning material, and when turned into steam it reduces the amount of oxygen in the air to feed the fire.
But water by itself may not be enough. The fires can spread insidiously beneath mosses and lichens, and can survive inside hummocks and old stumps to break out again days later. To reduce these ‘hot spots’, chemicals called wetting agents are mixed with water to help it to penetrate. And dyes may be added to show which areas of forest have been treated.
Ground crews may create firebreaks to contain the blaze, while air tankers ‘bomb’ the fire with up to 4400 gallons (20,000 litres) of water and chemicals. One way of getting firefighters to the scene is by parachuting them in.
`Smoke-jumping’, as the technique is called, is particularly useful in remote and rugged areas of the USA, where pine forests offer no great threat to parachutists.
American firefighters have been jumping into blazes since 1941. Now, the several hundred smoke-jumpers – there are 360 in the Pacific north-west alone – are the heroes of firefighting units in the mid-West and West.
Zooming down on their parachutes, they aim to isolate small fires before they spread. With fire raging below, air currents are chaotic, visibility is poor, and risks are high. In 1949, in Mann Gulch, near Helena, Montana, 13 smoke jumpers died when a fire suddenly changed direction, driven by the change of wind.
Once safely down, smoke-jumpers clear a path around the fire and fell dead trees, aiming to contain the blaze until it burns out or ground crews arrive.
Increasingly, firefighters appreciate that fire is not always an enemy. Fires caused by lightning are natural events that are vital to forest ecology, providing space for new species or protection for established ones. Forest giants like sequoias depend on regular small-scale fires to preserve an open area around them. Preventing all fires only encourages easily combustible spruces and firs to grow up beneath the sequoias, guaranteeing their destruction when fire eventually strikes.
In 1968, the US Parks Service began controlled blazes, both to imitate nature and to avoid larger, uncontrolled fires later. Sometimes, they allow naturally occurring fires to take their course, fighting back only to preserve lives, stock and property. Firefighters recognise that there is a limit to what they can do, as shown by the fires that swept South Australia and Victoria on Ash Wednesday, February 16, 1983.
For days, temperatures had been 104°F (40°C), and the countryside was tinder-dry. That afternoon, fires broke out 45 miles (72km) north-west of Melbourne, and near Adelaide, 400 miles (660km) to the west. Within two hours, there were 20 major fires in a 600 mile (960km) arc, whipped by 70mph (112km) winds that tossed tussocks of burning grass through the air like tumbleweed and sucked the walls out of houses. Some 21,500 volunteers fought the blazes, with 800 fire trucks and some 200 bulldozers to clear firebreaks. Flames 120ft (36m) high swept across the states, driven by oven-hot winds.
By the time the fires died down ten days later, they had destroyed almost 1 million acres (400,000 hectares) and 280,000 head of stock, caused $450 million worth of damage and killed 74 people. In these conditions, there is little anyone can do. Victoria’s Fire Brigade captain, Graham Simpson, commented that a major bushfire is ‘a cataclysm creating its own wind and weather, a demon with a mind of its own’.
Firefighting with foam
Some forest fires can best be fought with foaming agents. A firefighting amphibian flies low over the blaze, ringing it with foam.
Firefighting with water
A firefighting amphibian scoops water from a lake in Ontario, Canada. The planes can scoop up 1400 gallons (6400 litres) in ten seconds and make more than 200 flights in a day.