Wildfire:

A Wildfire or wild land fire is a fire in an area of combustible vegetation occurring in rural areas. Depending on the type of vegetation present, a wildfire can also be classified more specifically as a brush fire, bushfire, desert fire, forest fire, grass fire, hill fire, peat fire, vegetation fire, and veld fire.

Wildfires can be characterized in terms of the cause of ignition, their physical properties, the combustible materials present, and the effect of weather on the fire. Wildfires can cause damage to property and human life, though naturally occurring wildfires may have beneficial effects on native vegetation, animals and ecosystems that have evolved with fire. High-severity wildfire creates complex early seral forest habitat (also called “sang forest habitat”), which often has high species richness and diversity than unburned old forests. Wildfires in ecosystems where wildfire is uncommon or where non-native vegetation has encroached may have strongly negative ecological effects. Wildfire behavior severity results from the combination of factors such as available fuels, physical setting, and weather. Analyses of historical meteorological data and national fire records in western North America show the Primacy of climate in driving large regional fires via wet periods that create substantial fuels or drought and warming that extend conductive fire weather.

Types of Wildfire:

Forests have vegetation at different levels that can fuel fire activity the forest floor, understory and canopy.

Ground Fires: Ground fire is also called underground or subsurface fires. It occurs when accumulations of peat, hummus, tree roots, and other dead vegetation burn underground. This type of fire moves very slowly and tends to smoulder rather than produce flame. Ground fires are tough to contain and suppress because of their below-ground environment.

Surface Fires: Surface fire occurs within the lower level of the forest and does not scorch the canopy to the extent that it will carry a fire. Surface fires are common but are usually low intensity. They partially consume the “fuel layer” while presenting little danger to mature trees and root system. A buildup of fuel and vegetation on the forest floor can cause surface fires of higher intensity. In drought conditions, surface fires can transition into damaging ground fires.

Crown Fires: Crown fires are fast moving fire in the upper canopy of vegetation. Crown fires involve the burning of vegetation both at the surface and crown fuel layer farther up the tree. The “ladder effect” causes hot surface or ground fires to climb up into the canopy. Crown fires are most common in coniferous forests and chaparral-type shrublands.

Because crown fires affect multiple levels of vegetation, they are often fast moving and extreme intensity fires. Wind conditions have a larger impact on the spread of canopy level fires high wind conditions can cause flames to spread along interconnected and continuous foliage incredibly quickly.

Spotting Fire:Spotting fire occurs when the burning particles of an existing fire are carried by the wind to start new fires outsides the zone of direct ignition of the original fire. Both wild land and structures fires generate particles which have the potential to be carried away and start additional spot fires.

“Ember” describes any small, hot, carbon-based particles, but the term “firebrand” is used to describe small airborne particles carried by an airstream that are the cause of spotting. Spotting can occur in both short and long range forms. The distance of travel and speed of spotting depends on factors such as the forest environment (height, width, and type of tree species, canopy cover), type of terrain, and wind speed.

• Short-range spotting: when firebrands land and ignite close to the path of the original fire. Not considered a significant factor in fire spread because the fire usually quickly overruns the developing spot fire.
• Long-range spotting: when travel of firebrands beyond the main fire site. Often caused by the lofting of firebrands in a convection column.

Causes:

Natural causes of wildfire:

Dry Climate: – Dry climates, particularly during prolonged droughts, create ideal conditions for wildfires.

• Low Moisture Level: In dry climates, vegetation such as grass, shrubs, and tress lose moisture and become highly flammable. Even small sparks can ignite dry plants.
• High Temperatures: Heat accelerates the drying process, making the environment more susceptible to fires.
• Lack of Rainfall: Extended periods without rain mean that natural water sources are unable to replenish the moisture in vegetation and soil.
• Winds in Dry Climates: Winds in arid regions not only fan flames but also carry embers over long distance rapidly spreading fires.

For example, regions like California, Australia and the Mediterranean often experience wildfires due to their dry climates combined with seasonal winds and heat waves.

Volcanic eruption: – Volcanic eruptions are a natural cause of wildfires, primarily due to the following:

• Lava Flows: Lava from an erupting volcano can ignite any vegetation it comes into contact with. Lava flows are extremely hot (up to 2200⁰F or 1200⁰C) and capable of setting large areas ablaze.
• Ash and Hot Rocks: Ejected volcanic materials, such as hot ash or rocks, can fall onto dry forests or grasslands, sparking fires.
• Gas Emission: Volcanic eruptions release gases like sulphur dioxide, which can interact with the environment to create lightning. This volcanic lightning can ignite fires over wide areas.

For example, in 2018 eruption of Kilauea in Hawaii, where lava flows ignites vegetation and caused wildfires around the area. Similarly, volcanic activity in Indonesia and Iceland has also resulted in wildfires in the past.

Lightning: –Lightning is the most common ignition source that causes the vast majority of wildfires. There are two types of lightning:

• Cold lightning: Cold lightning is usually of short duration and thus rarely a cause of wildfires.
• Hot lightning: Hot lightning have less voltage but occur for a longer period of time. Because, of the intense heat it generates, hot lightning accounts for the majority of natural fires.

While this natural phenomenon is completely unpredictable, adequate land management and landscape fire management planning can significantly diminish the intensity of wildfires and prevent unnecessary deaths and the displacement of people and animals.

Climate change is undoubtedly the biggest trigger of extreme lightning storms. Warmer and longer summers heat up the land surface. This, coupled with an increase in carbon emission, caused stronger updrafts that are more likely to produce more powerful and frequent lightning.

Human Induced wildfire:

Humans are also often responsible for initiating wildfires, either accidentally or intentionally. Human-related events that can ignite fires range from open burning such as campfires, equipment failure, and the malfunction of engines to debris burning, negligent discarding of cigarettes on dry grounds as well as other intentional acts of arson.The latter accounts for one of the most common causes of wildfires.

Spread:

The spread of wildfire varies based on the flammable material present, its vertical arrangement and moisture content and weather conditions. Fuel arrangement and density is governed in part by topography, as land shape determines factors such as available sunlight and water for plant growth. Overall, fire types can be generally characterized by their fuels as follows:

• Ground fires are fed by subterranean roots, duff and other burned organic matter. Ground fires typically burned by smoldering, and can burn slowly for days to months such as peat fires in Indonesia.
• Surface fire is fueled by low-lying vegetative matter on the forest floor such as leaf and timber litter, debris, grass, and low-lying shrubbery. This kind of fire often burns at a relatively lower temperature than crown fires (less than 400⁰C (752⁰F)) and may spread at slow rate.
• Crown, canopy fires burn suspended material at the canopy level such as tall trees, vines and mosses. The ignition of the crown fire, termed crowing is dependent on the density of the suspended material, canopy height, canopy continuity, sufficient surface and ladder fires.

Prevention:

Wildfire prevention refers to the preemptive methods aimed at reducing the risk of fires, as well as lessening its severity and spread. Prevention techniques aim to manage air quality, maintain ecological balance, protect resources, and to affect future fires. North America firefighting policies permit naturally caused fires to burn to maintain their ecological role so long as the risks of escape into high value areas are mitigated. However, prevention polices must consider the role that humans play in wildfires, since, for example, 95% of forest fires in Europe are related to human involvement.  Sources of human caused fire may include arson, accidental ignition, or the uncontrolled use of fire in land-clearing and agriculture such as the slash-and-burn farming in Southeast Asia.

Wildfire itself is reportedly “the most effective treatment for reducing a fire’s rate of spread, fire line intensity, flame length and heat per unit of area”. Building codes in fire-prone areas typically require that structures be built of flame-resistant materials and a defensible space be maintained by clearing flammable materials within a prescribed distance from the structures.