**3. Forest fire**

The fire is usually used to clean lands, e. g. the preparation for planting or pasture. According to Medeiros (2002), a forest fire is a fire that starts in several types of vegetation, running out of control, which can be intentionally started or have natural causes such as sunlight. Large forest fires can be considered a serious threat to biodiversity conservation and the maintenance of ecological processes. This threat is particularly serious for small areas, sections isolated by cities or agricultural monocultures and areas with rare and/or endangered species, because these ecosystems are very susceptible to fire.

The risk and intensity of damage are vary depending on the size of the area, age, intensity of the fire and time of year. Fires have been a matter of continuous concern in the dry season, when most of the damage to the ecosystem could be experienced in cities located in the referred area, which were covered by smoke and ash (Medeiros, 2002).

In Brazil, the causes of forest fires in the Cerrado were mostly associated to incorrect use of firefighting equipment: lack of fire lines, climate conditions and lack of fire control equipment. Also, illegal burning is one important cause of these fires. Recent studies have shown that 67% of the burned areas in Brazil (in 2000) were in Cerrado (Tansey et al. 2004).

According to Vicentini (1993) and Silva et al. (2009) the Cerrado has been increasingly occupied and converted into agricultural land. The author affirms that the Conservation Units located in this biome have been constantly impacted by the action of frequent forest fires. Intensive agriculture is one of the factors that contribute to the generation of Conservation Units of small areas, which presents one or more vulnerable characteristics due to the occurrence of fires, as previously mentioned.

Besides releasing carbon dioxide (CO2) into the atmosphere, burning can release other gases that cause global warming, and high frequency of fire affects the establishment of trees and shrubs (Hoffmann & Moreira, 2002, Krug et al., 2002).
