VARIETY

What causes

wildfires?

Most of you must be aware of the major fires that break out in large forested areas in various parts of the world destroying vast extents of land. Both animal and man are adversely affected by these fires that occur most often without any human intervention. Even in Sri lanka such fires destroy valuable forest cover. Recently a fire broke out in the Knuckles Range. Forests are an intregal part of the environment and when they are destroyed ,the ecological- balance of that region too is disturbed.

Let us find out how such wild fires happen..

Any uncontrolled fire that satrts in a wild habitat is called a wildfire, bushfire or forest fire. Such wildfires take place all over the world. Major fires are reported every few years in the forests of the United States and Indonesia, and also in the bush in Australia.Wild fires can happen due to three reasons.

They can be accidental, deliberate( caused by arson ) or by lightning strikes and volcanic eruptions. Besides these, sparks from rockfalls can also ignite forest fires. When a heat wave or drought has dried out the plants in an area a fire sparked off by anyone of the three methods mentioned here can spread quickly. Because fires can be very destructive, firefighters have developed lots of strategies for extinguishing or controlling wildfire. Forest fires happen mainly in the summer and autumn and are particularly destructive when there is a drought because branches and twigs die and dry out, creating plenty of fuel for the fire. Sometimes forest fires can be spontaneous due to hot and dry weather.

The three essential requirements for fires are oxygen, fuel and heat. There is no dearth (scarcity) of oxygen in the forest, while the woods and the dry fallen branches and leaves serve as fuel. So, together they speed up the spreading of the fire. Besides, it has also been found that at very high temperatures, woods produce a gas that reacts with oxygen to ignite a flame. If you are wondering as to how such a fire spreads across the forest so quickly with its flames virtually swallowing up everything in its path, it is due to the wind.

The way the wind blows is a major factor when it comes to containing (restricting) the spread of such fires. Sometimes even firefighters are unable to take any remedial measures because of strong winds.

Wind is a major factor. Some fires spread along the dead leaves and branches at the bottom of trees.

Some fires spread when the leafy canopy catches fire. Also, burning leaves and branches can get blown ahead of the main fire causing smaller fires to start. Planes and helicopters are often used to drop water and chemical fire retardant into affected ares.

But when the fires are blazing and the wind carries the flames higher and higher into the skies even the planes and helicopters cannot do anything to control the fires from the air. However, on the ground firefighters will struggle to contain such fires by creating a control line an area where they remove all the fuel so that the fire cannot travel across it.

This can be a barrier like a river or road. They then cut down dead trees to stop them falling across the fire line.

Drip torches are used to burn the plants between the control line and the fire to remove the fuel.Generally, wildfires bring negative effects but you will be amazed to learn that some positive results too could be obtained from a wildfire. For instance, in the United States they used to have a policy of putting out all forest fires. However, in the 1960s they realised that there were no new giant sequoia trees growing. They grow in the Western USA and have a larger diameter than any other tree species in the world. Forest fires are a crucial part of their lifecycle.

Fires take warm air up into the tops of the trees, which dries the cones and makes them split, allowing the seeds to pop out. Fire also clears the undergrowth allowing the seeds to germinate. To allow these processes to continue, the authorities started creating controlled fires and allowing natural fires to burn. Mild forest fires are often considered beneficial, as growth of many plant species depend on it. Many plant species also depend on wildfires for reproduction, as the exposure to smoke induces germination in these plants.

However, the large forest fires can have serious damaging effect on the surrounding environment Forest fires can affect climate and weather a great deal, besides causing severe damage to valuable trees. It can increase the level of greenhouse gases (water vapour, carbon dioxide, methane, nitrous oxide, ozone, and chlorofluorocarbons), and thereby increase pollution and global warming. However, it is an important part of the ecosystem, and many plants depend on it for growth and reproduction.

But, too much of wildfires can cause significant damage to the ecosystem.

Facts: Internet