This image shows in red the extent of areas in Africa affected by seasonal fires between April 2010 and March 2011.
Savannah areas on both sides of the equator are particular prone to yearly fires. Part of these are natural fires while another part are lit by man. The background image is a composite of daily data acquired by the SPOT VEGETATION sensor between 1998 and 2008.
Africa is often called the "continent of fire". It is estimated that of the 750 million hectares of vegetation burnt yearly, nearly half occur in Africa. Globally, the most affected areas are East Africa, Central Africa and Southern Africa.
Although wildfires are happening throughout the year in Africa, over 90% of fires occur during the dry season. Dead or dormant vegetation and trees that lost their leaves produce an accumulation of combustible materials on the ground.
These fires may be accidental, but more often they are triggered by people voluntarily. Fire is indeed traditionally used as a tool for land management. For agricultural land, fires are used to clear and remove dried residue. For grazing, fire is the main agent of decomposition that allows the return of nitrates in the soil while maintaining high productivity of the land. Fires are also used to guide the game or to reduce the risk of unplanned fires.
The fires, even voluntarily induced, are not always controllable. They can spread rapidly and cover large areas. The abundance of dry vegetation, low population density and lack of areas that can act as a firewall are all reasons why the fires easily spread.
The fires can therefore cause extensive damage and even loss of life. They also have a major impact on global change, as they are responsible for significant emissions of greenhouse gases and aerosols. Savannah and forest fires release nearly 3.5 billion tons of CO2 and 17.5 million tons of particles, corresponding respectively to 42% and 49% of emissions from fires in the world.
These reasons justify the increasing interest in the study of wildfires. Today, remote sensing appears to be a valuable tool for monitoring fires and for the objective assessment of their emissions.