The picture above shows a wildfire in Brazil’s Cerrado ecoregion. Such conflagrations are usually man-made, but wildfires can also start naturally.
Dry forest debris can catch fire, and lightning strikes may ignite fires. There are positive aspects to less destructive forest fires, however. Old growth and weeds are burned off, stimulating regeneration. Minerals and nutrients are released from burning plants and returned to the soil. Forest canopies are opened up too, allowing more sunlight to reach plants on the ground.
r The area devastated
hv the 1871 wildfire in
Belgium – or twice the size of Kuwait.
In Apr 2004, scientists from Cardiff University’s School of Earth, Ocean and Planetary Science (UK) found evidence that a low-intensity wildfire began smouldering c. 419 million years ago, in the Silurian period. The fire was likely started by a lightning strike. The discovery was made while the team was studying charred fossils of small plants found in rocks near Ludlow, UK.
The fire in a burning coal seam beneath Mount Wingen in New South Wales, Australia, is believed to have started 5,000 years ago. It ignited when lightning struck the seam at the point where it reached the Earth’s surface. Today, the fire is burning around 100 ft (30 m) underground, as it has slowly eaten away at the seam.
The last resort used by firefighters faced with wildfires that have surrounded them is to build a fire shelter. Designed to reflect heat, keep out convective heat and contain breathable air, they resemble a shallow one-person tent and are deployed on the ground or in a dug-out hollow. The earliest known use of a fire shelter was noted by explorer William Clark in a journal entry dated 29 Oct 1804. Reporting the outbreak of a prairie wildfire near Fort Mandan in North Dakota, USA, Clark related an incident in which an American mother threw a “Green buffalow Skin” [sic] over her son to protect him from the flames.
The heat content of any fire depends upon wood density, resin, ash and moisture, but the tree that produces the most heat when burned is the osage-orange or horse-apple (Maclurapomifera), a large deciduous shrublike plant belonging to the mulberry family, and distributed widely across North America.
V When burned, this species produces some 34.8 billion joules per 20% air-dried moisture content cord. A cord is defined n ll as a piece of wood 4 ft wide by 4 ft high
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by 8 ft long (1.21 m x 1.21 m x 2.43 m), with an average 80 cu ft (2.2 m3) of burnable wood, the remainder being pockets of air.
A firebreak is a break in vegetation that acts to block the progress of wildfires. Man-made firebreaks are often created in the form of roac strategically constructed in places at high risk of wildfires. In 1931, construction began on the Ponderosa Way on the western slope of the Sierra Nevada Mountains in California, USA. Eventually reaching a length of some 800 mi (1,287 km) – around the same as the Rhine river – the Ponderosa Way was built by around 16,000 members of the Civilian Conservation Corps. In 1934 alone, the firebreak was responsible for containing nine of the 11 large wildfires that hit the region that year.
Smokejumpers are elite firefighters who are deployed to remote wildfires as soon as they are identified. They are dropped by parachute near a wildfire, along with their equipment, including food and water to make them self-sufficient for a day or two.
Once deployed, smokejumpers use chainsaws and other equipment to cut down trees, scrape away topsoil and create firebreaks. Russia, which introduced smokejumpers in around 1936, currently employs approximately 4,000 of them.
More than 80% of wildfires are begun by humans – either deliberately or by accident
China, the world’s largest producer of coal, has hundreds of subterranean fires across its coal belt. Some have been burning for centuries. Around 20 million tonnes (19.6 million tons) of coal per year are destroyed and 10 times that amount rendered inaccessible owing to the fires.
nCMtW’; ‘d HIGHEST DEATH TOLL FROM A WILDFIRE
On 8 Oct 1871, forest fires ravaged north-east ‘ ■■ Wisconsin and upper Michigan, USA, killing around ■’ . 1,200 to 2,500 people. More than 1,500 sq mi
■, (3,885 km^) of forest and farmland were also
^ destroyed (see illustration, left).
^ Under certain circumstances, tornado-like
‘■ .>* phenomena known as “fire whirls” can occur within
‘ fires. They are caused by heat rising and forming
eddies. The highest death toll from a fire whirl happened as a result of the Great Kanto Earthquake on 1 Sep 1923, which struck the Kanto region of Honshu in Japan (see ^ photograph, far left). Tragically, 38,000 people were incinerated by a fire whirl while packed into a former army clothing depot in Tokyo.
American football fields every day!
A WORSTYEAR FOR DESTRUCTION OF THE NATURAL ENVIRONMENT BY FIRE
According to the World Wide Fund for Nature, forest fires that had been deliberately lit made 1997 the worst year in history for the devastation of the natural environment. The largest and most numerous were in Brazil, where they raged along a
1,000-mi (1,600-km) front. Although the droughts in the Amazon Basin and Southeast Asia (caused by the El Nino effect) were partially to blame for the forest fires, the deliberate lighting of fires to clear forest was the main cause of the disaster.
Boeing 747-400 drops its load from a height of just 120-240 m (393-787 ft), travelling ^ at around 260 km/h , (160 mph).
A LARGEST FIREFIGHTING AIRCRAFT
Global SuperTanker Services uses a converted Boeing 747-400 jumbo jet as an aerial firefighter. The aircraft can transport 74,200 litres (19,601 US gal) of water or fire retardant.
Introduced in 1994, the Mi-26TP is the largest firefighting helicopter at 33.73 m (110 ft 7 in) long, with a maximum takeoff weight of 56 tonnes (123,459 lb). It can be equipped with the VSU-15 water drop system – essentially a sack of tough parachute material that can be lowered into a reservoir and filled with 15 tonnes (16.5 tons) of water in around 30 sec.
A FIRST DOCUMENTED FIRE TORNADO
Fire tornados are formed from pyrocumulonimbus clouds (see right). On 18 Jan 2003, a fire tornado arose in the plume of the McIntyres Hut fire, part of the Jan 2003 Canberra fires in Australia. It moved at around 30 km/h (18.6 mph), measured nearly 0.5 km (0.3 mi) at its base, and was strong enough to move cars and tear off roofs.
A HIGHESTCLOUDS FORMED BY WILDFIRES
The intense heat from wildfires can make weather. The powerful updrafts of air can carry water vapour and ash high into the atmosphere, creating a type of cumulus cloud known as pyrocumulus. These clouds can reach around 10,000 m (32,800 ft) in height.
Even more powerful are pyrocumulonimbus clouds (above), which can reach altitudes of around 16,000 m (52,490 ft).
In this picture, ■■ a firefighter
fire flames, having
turned a sapiing into
for his spade
According to Greenpeace, as of Jun 2016 wildfires covered some 35,000 km^ (13,513 sq mi) of Siberia. Recent very dry weather has exacerbated Siberia’s seasonal wildfires. Climate change in Russia is almost certainly to blame; from 1976 to 2012, the average temperature rose by more than twice the global average. Siberia is one of Earth’s most forested regions, containing great biodiversity and species such as bears, wolves and golden eagles.