Final 2

An uncontrolled fire in a wild habitat is termed as Wildfire. Wildfire also known as bushfire, forest fire, grass fire, hill fire, desert fire, peat fire, brush fire or veld fire usually occurs in an area of combustible vegetation. The various terms are used to describe the same depending on the type of vegetation that is burnt, as wildfire usually differs from other fires due to its extensive size, the speed at which it burns and spreads out from its initial source, its potential to change directions and its ability to cross gaps like roads or rivers. Wildfire usually starts unnoticed, but gradually spreads at a quick speed burning down thousands of acres of land, trees, homes, humans, animals or anything that comes in its path.

What causes a Wildfire?

Various reasons contribute to a fire in an area of combustible vegetation. The four major natural reasons which ignite fire are volcanic eruption, lightning, sparks from rock falls and spontaneous combustion. The other reason that leads to disasters like Wildfire are attributes to human sources like arson, discarding a lit cigarette, playing around with matches or fireworks, sparks from equipments and prescribed fires. The cause of Wildfire usually varies throughout the world. Some of the other causes of Wildfire are droughts, heat waves and cyclical climatic changes like the El Nino. It is believed that four out of every five Wildfires are caused by human.

Where and when can a Wildfire occur?

Wildfires can occur anywhere in the world, but are more common in forested areas. Fires are more prevalent in the summer season, autumn and during droughts when leaves, branches and other materials from the trees fall out and become highly flammable. They are more destructive during droughts as the branches and twigs die and dry out, creating ample of fuel for the fire to ignite. Wildfires are also common in grasslands and scrublands.

Which conditions lead to disasters like Wildfires?

For a Wildfire to burn, three conditions are required. It is often referred as a fire triangle by the fire-fighters: the heat source, oxygen and the fuel. Fuel is any flammable material around the fire, which includes dry leaves, twigs, grasses or even homes. The fire is more intense, if the fuel load of that particular area is more. Small fuel load will cause a fire to burn and spread at a slow intensity. The dryness of the fuel at times also affects the behaviour of the fire, because when the fuel is very dry, it is burnt and consumed at a faster rate, creating a fire which is much more difficult to contain. Air supplies all the oxygen which is required for a fire to burn, whereas the heat sources help spark the Wildfire. Burning campfires, discarding a lit cigarette, hot winds or even the sun at times provides all the necessary heat to spark a Wildfire.

Why do Wildfires spread so quickly and what are its types?

The Wildfires spread based on various flammable materials present around and their arrangement. Generally the fire types are characterized by the fuels:

  • Ground Fires: They are usually fed by subterranean roots, duff and other buried organic matter, which are basically more susceptible to ignition due to spotting. They burn at a slower rate from days to months.

  • Crawling or Surface Fires: They are usually fed by low-lying vegetation like the leafs, timber, grass, debris and low lying shrubs.

  • Ladder Fires: They usually consume materials between tree canopies, like small tress, logs and vines. They also consume materials like low-level vegetations. Wild climbing fern and other invasive plant species encourage ladder fires.

  • Crown or Aerial Fires: They usually burn materials at the canopy level, such as mosses, vines or even tall trees. It is usually dependent on the height, the continuity and a sufficient surface.

Wind is a major factor in spreading of the fire. Some fires also spread along the dead leaves and branches which are at the bottom of the trees. Sometimes when the leafy canopy catches fire, it helps the fire to spread too. Wildfires are usually fuelled by the weather conditions, and the wind which can help burn acres of land and consume anything in its path, in just a few minutes.

What role does the weather play in Wildfires?

In the birth, growth and the death of a Wildfire, weather plays a crucial role. Drought conditions lead to extremely favourable conditions for Wildfires, and wind aids the Wildfire’s progress, whereas the weather can help the fire to move at a faster rate; engulfing more land. There are three weather ingredients which usually affect Wildfires:

  • Temperature

  • Wind

  • Moisture

The temperature usually affects what sparks the Wildfires, as heat is one amongst the three pillars of the fire triangle. As the sticks, trees and the underbrush on the ground receive excessive heat from the sun, which in turn heats and dries potential fuel. Warmer temperatures help the fuels to ignite and burn at a faster rate. Wildfires usually tend to rage during the afternoons, when the temperatures are at their peak. Besides the temperature, wind is one of the major factors that have a big impact on Wildfires behaviour. Wind is also one of the most unpredictable factor. It supplies the fire with additional oxygen, initiating the fire to spread across the land at a faster rate. The stronger the wind blows, additional level of oxygen is provided, which in return allows the fire to spread at a faster rate. Winds at times also help in changing the direction of the fire. Gusts are also created due to the wind which can raise fire into the trees, creating a crown fire. As wind helps the fire to spread, moisture works against the fire. In form of humidity and precipitation, moisture usually slows down the fire and reduces its intensity. If there is high level of moisture, the potential fuels are hard to ignite; as the moisture absorbs the fire’s heat. Similarly, when the humidity is low, Wildfires are more prone to start. As moisture reduces the chances of Wildfires, rainfall has a direct impact on preventing the fire. As when the air becomes saturated with moisture, it releases the moisture in the form of rainfall.

What are the effects of Wildfire on Soil?

The effects of Wildfire on the soil are usually dependent on the amount of heat that is transferred into the ground during a fire. It is not necessary that high-intensity fires can have a great impact on the soil, as in some cases during high-intensity fires, the fires move quickly through the tree canopies and have a less impact on the soil; whereas low-intensity fires usually smolder around the ground for a longer period of time. The severity of the fire describes the effects of fire on various different components of ecosystem; including its chemical, biological and physical properties. Disturbance in these components of ecosystem due to Wildfire can affect the soil nutrients, may alter the water retention capacity of the soil and can also cause soil erosion. Such a variety changes due to Wildfire can decrease or modify the productivity of the soil. There are adverse effects of Wildfire on the hydrological cycle too, for example, reduced vegetation can give rise to significant flooding, soil erosion, and also some significant changes in the water temperature.

What is the global impact of deforestation due to Wildfires?

On our planet, forests cover about 31 percent of the land. They are very important as they produce vital oxygen, provide home for humans as well as animals. Many of the world’s endangered and threatened species live in the forests. And about 1.6 billion people totally rely on forests for food, fresh water, clothing, shelter and even for traditional medicines. Deforestation comes in many forms, which includes fires, degradation due to climate change, and clearing the land for agriculture.

The effects of deforestation are:

  • Reduced bio-diversity: Deforestation can lead to decline in bio-diversity. When deforestation occurs in any form, the wildlife is affected; they get deprived of their habitat and are more prone to hunting.

  • Release of greenhouse gas emissions: About 15 percent of the global greenhouse gas emission is due to deforestation.

  • Disrupted water cycles: Due to deforestation, trees no longer evaporate ground water, which can lead to much drier climate.

  • Increased soil erosion: The rate of soil erosion is increased due to deforestation.

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