Fig. 3. Relationship between (a) fire frequency and burned area; (b) fire frequency and risk of forest fire, in the Beça River basin.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 4. Plot of burned area (period 1990–2013) versus class of wildfire risk (evaluation in 2011), considering the frequency of wildfires in that SAR191801 period: (a) one occurrence, (b) two occurrences, (c) three occurrences and (d) four occurrences; the five occurrence diagram has not been represented because of its limited spatial coverage and doubtful statistical significance. In the trend line equations, variable n represents the class of wildfire risk: 1 — low, 2 — low-moderate, 3 — moderate, 4 — high, 5 — very high.Figure optionsDownload full-size imageDownload as PowerPoint slide
As evidenced in Fig. 2a, 16,396 ha of land were burned between 1990 and 2013, which corresponds to 47% of the basin area. A major portion of sedimentary rock land was represented by shrub land (69%) and forests (22%), with the remaining 9% being mostly represented by heterogeneous agricultural areas (usually, a mosaic of farmlands and shrub lands, with isolated spots of forests). The maxima of burned area occurred in 2005, 2009 and 2010, with values above 2000 ha (Fig. 5). In 2010, the burned area (5000 ha) approximately doubled the area consumed by fire in 2005 (2440 ha). Besides, the areas burned in the last decade (58% of total burned area) were much more extensive than the areas burned in the previous 15 years (42%).