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The Copernicus Sentinel-3A satellite captured this image of smoke from wildfires in the US state of California on 9 October 2017. Image: contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO.

Definition

Wildfire, also called forest, bush or vegetation fire, can be described as any uncontrolled and non-prescribed combustion or burning of plants in a natural setting such as a forest, grassland, brush land or tundra, which consumes the natural fuels and spreads based on environmental conditions (e.g., wind, topography). Wildfire can be incited by human actions, such as land clearing, extreme drought or in rare cases by lightning (IRDR).

There are three conditions that need to be present in order for a wildfire to burn: fuel, oxygen, and a heat source. Fuel is any flammable material surrounding a fire, including trees, grasses, brush, even homes. The greater an area's fuel load, the more intense the fire. Air supplies the oxygen a fire needs to burn. Heat sources help spark the wildfire and bring fuel to temperatures hot enough to ignite. Lightning, burning campfires or cigarettes, hot winds, and even the sun can all provide sufficient heat to spark a wildfire (National Geographic).

Facts and figures

The Global Wildland Fire Network Bulletin published by the Global Fire Monitoring Center (GFMC) presents the most recent data regarding consequences of wildfire: in 2017, 36 fires in protected areas were recorded in 19 countries burning more than 196000 hectares worldwide.

Wildfire plays a mixed role for ecology and economy since some ecosystems depend on natural fires to maintaining their dynamics, biodiversity and productivity. However, every year, wildfires burn millions of hectares of forest woodlands and other vegetation, causing the loss of many human and animal lives and an immense economic damage, both in terms of resources destroyed and the costs of suppression. There are also impacts on society and the environment, such as damage to human health from smoke, loss of biological diversity, release of  greenhouse gases, damage to recreational values and infrastructure (FAO).

Most fires are caused by people. The list of human motivations include land clearing and other agricultural activities, maintenance of grasslands for livestock management, extraction of non-wood forest products, industrial development, resettlement, hunting, negligence and arson. Only in very remote areas of Canada and the Russian Federation lightning is a major cause of fires (FAO).

There are three basic types of wildfires:

  • Crown fires burn trees up their entire length to the top. These are the most intense and dangerous wildland fires.
  • Surface fires burn only surface litter and duff. These are the easiest fires to put out and cause the least damage to the forest.
  • Ground fires (sometimes called underground or subsurface fires) occur in deep accumulations of humus, peat and similar dead vegetation that become dry enough to burn. These fires move very slowly, but can become difficult to fully put out, or suppress (Government of Canada).

Further information

FAO International Handbook on Forest Fire Protection
UNDRR Wildfire Hazard and Risk Assessment
WWF Report - Forests Ablaze. Causes and effects of global forest fires
The European Forest Fire Information System (EFFIS)
The Global Wildfire Information System (GWIS)

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Term Parents

Climatologique

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