Lightning Fires in a Brazilian Savanna National Park: Rethinking Management Strategies

Abstract

Fire occurrences and their sources were monitored in Emas National Park, Brazil (17°49'-18°28'S; 52°39'-53°10'W) from June 1995 to May 1999. The extent of burned area and weather conditions were registered. Forty-five fires were recorded and mapped on a GIS during this study. Four fires occurred in the dry winter season (June-August; 7,942 ha burned), all caused by humans; 10 fires occurred in the seasonally transitional months (May and September) (33,386 ha burned); 31 fires occurred in the wet season, of which 30 were caused by lightning inside the park (29,326 ha burned), and one started outside the park (866 ha burned). Wet season lightning fires started in the open vegetation (wet field or grassy savanna) at a flat plateau, an area that showed significantly higher fire incidence. On average, winter fires burned larger areas and spread more quickly, compared to lightning fires, and fire suppression was necessary to extinguish them. Most lightning fires were patchy and extinguished primarily by rain. Lightning fires in the wet season, previously considered unimportant episodes, were shown to be very frequent and probably represent the natural fire pattern in the region. Lightning fires should be regarded as ecologically beneficial, as they create natural barriers to the spread of winter fires. The present fire management in the park is based on the burning of preventive firebreaks in the dry season and exclusion of any other fire. This policy does not take advantage of the beneficial effects of the natural fire regime and may in fact reduce biodiversity. The results presented here stress the need for reevaluating present policies and management procedures concerning fire in cerrado conservation areas.

Threats to the Cerrado remnants of the state of São Paulo, Brazil

“…Only 9% of all sites in this study had been totally burned, 12% were partially affected by recent fires and 79% had no evidences of fire at all ( Figure 2B). There is a debate on the negative effects of fire on the Cerrado ecosystem, since it has been recorded since the arrival of the first inhabitants in South America (Dean, 1995) and even before that, caused by natural causes (Ramos-Neto & Pivello, 2000;Miranda & Sato, 2005). Some authors point out benefits of fire to the Cerrado ecosystem (e.g.…”

“…Coutinho, 1990). However, the increase in fire frequency and modification of the fire season can have negative effects on the regeneration of woody plants, favouring the herbaceous layer (Hoffman, 1999;Hoffmann & Moreira, 2002;Klink & Moreira, 2002), thereby changing both plant and animal communities (Durigan et al, 1994;Sato & Miranda, 1996;Hoffmann, 1998;Ramos-Neto & Pivello, 2000;. Protection against fire favours the Cerrado physiognomies to become denser, as observed in a number of areas (Goodland & Ferri, 1979;Ratter et al, 1988;Ratter, 1992;Moreira, 2000; and these changes seem to be the natural direction towards a new climax for most of the Cerrado remnants, especially in the São Paulo State.…”

Influence of fire history and soil properties on plant species richness and functional diversity in a neotropical savanna

“…The ENP is under a tropical warm wet climate, with at least three dry months during the winter. Annual rainfall is 1200-2000 mm, concentrated in the period from October to March (Ramos-Neto & Pivello 2000). Soils at the ENP are mainly nutrient-poor oxisols (Amorim & Batalha 2007;Silva & Batalha 2008).…”

“…Until 1984, farmers exploited the ENP for cattle ranching, and dry season burnings were used in order to promote forage regrowth every year. After 1984, the ENP was totally fenced, cattle were no longer allowed inside it, and a fire exclusion policy was established (Ramos-Neto & Pivello 2000). Since 1994, annual prescribed burnings have been applied in approximately 10 km 2 of preventive firebreaks to remove plant dry mass and avoid the spread of fires, which in the past resulted in catastrophic burn events every three years (Ramos-Neto & Pivello 2000).…”

Woody encroachment and its consequences on hydrological processes in the savannah

“…The Cerrado biome is a dynamic mosaic of vegetation types with varying biomass that can be related to environmental conditions [34], but has been maintained by fire at different frequencies [35,36]. In addition to natural fires caused by lightning [37], the whole Cerrado biome was historically burned by Indians once every 5-10 years and in the last three centuries it was burned every 1-2 years by ranchers [38]. In recent decades, however, fire frequency in the Cerrado remnants has been reduced, leading to woody encroachment where no abiotic limitations exist for biomass accumulation.…”