Variabilidade atmosférica e suas consequências na determinação do fogo na Região Sul do Brasil

Abstract

Fire played an important role in the formation and is still important for maintaining the structure and plant composition of different ecosystems. The occurrence of the element is influenced by weather variations that may condition the combustible material. Nowadays, the alteration of the landscapes through the different anthropic activities and man-made climate changes have tampered with the natural occurrence of fire. The use of uncontrolled fire by humans associated with favorable burning conditions has caused social, economic and environmental damage in different parts of the world. The objective of the present study was to evaluate the variations in the occurrence of fire in the Southern Region of Brazil caused by the seasonal characteristics of the years, as well as the environmental variation given by El Niño Southern Oscillation (ENSO). Moderate-Resolution Imaging Spectroradiometer (MODIS) fire products were associated with meteorological elements and vegetation cover data, and carbon emission data provided by the Global Fire Emissions Database (GFED) were evaluated. The correlation between meteorological elements and fire was obtained by the nonparametric Spearman method. In addition, the Mann Kendall statistical test was performed with the harvested area extensions of three temporary crops over 28 years. Fire in southern Brazil is mainly correlated with a reduction in rainfall and relative humidity in conjunction with rising atmospheric pressure and increasing wind speed. The periods under the cold phase of the phenomenon (La Niña) presented 26% to 114% more fire foci than those under the warm phase (El Niño). La Niñas also had 7% to 77% more burned area than El Niños. Plant coverings most affected by fire were those related to agricultural activity. La Niña events emitted more carbon into the atmosphere than El Niño occasions, with the largest difference observed between La Niña 2007/2008 (1.5097 Tg) and El Niño 2015 (0.6467 Tg). Mann Kendall statistics pointed out that Sugarcane, a highly flammable straw crop, showed a tendency to expand in the state of Paraná between 1990 and 2018. Continued crop expansion can be a fire hazard when combined with favorable burning conditions. Finally, it was possible to observe that the intra and interannual atmospheric variations and the mosaic of different vegetation cover determined the fire regime in the study area during the evaluated period