For a fire to start, three elements must be present: heat, fuel and oxygen. Together they form what is called the "fire triangle". The heat is the spark or the source that causes the fuel to ignite. It can be caused by people, such as lighting a match, or by natural causes, such as lightning. The fuels are vegetation, such as trees, leaves and twigs on the ground or other materials that can burn. Oxygen is a component of the air necessary for combustion. These three elements must be present for a fire to ignite and continue to burn. If only one or two of these components is present, a fire cannot start.
To control or extinguish a fire, at least one element of the fire triangle must be removed. Extinguishing a fire - either containing or extinguishing the fire - is successful when the fire triangle is broken by removing heat, fuel or oxygen.
An uncontrolled forest fire can devastate everything in its path, spreading for miles, crossing rivers and roads. Each year, between 60,000 and 80,000 forest fires occur, destroying between 3 and 10 million hectares. While forest fires have different consequences on the environment, depending on their importance and frequency, the causes are also diverse.
Lightning is attributed to be the main cause of the outbreaks of forest fires of natural origin. For example, it represents nearly 30 percent in Quebec! 43 percent of forest fires caused by humans are linked to carelessness (carelessly discarded cigarette butts, garbage dumps, burning). They can also occur as a result of power surges and damage to power lines.
Forest fires increase the levels of carbon dioxide in the atmosphere, contributing to the greenhouse effect and climate change. In addition, the ash destroys much of the nutrients and erodes the soil, causing flooding and landslides.
The use of chemicals in firefighting adds another problem to the already dramatic consequences of forest fires. According to a recent study by the Higher Council for Scientific Research (CSIC), the chemicals in “flame retardants " used to extinguish fires accumulate in the soil for years and stunt the natural growth of native species.