Effects of biomass burning on the lower atmosphere in transition cerrado-forest ecosystems

Abstract

Biomass burnings in the tropics in Brazil are a seasonal event. Every dry season, which occurs between June and October, large areas in the Cerrado are burned. The combustible material in this region is composed of grass, sedge, bushes and small trees. It is estimated that around 30 per cent of this region, which is of the order of 3 million square kilometers, is affected by the burning each year. In recent years, tropical countries were severely criticized by the international community for the occurrence of large numbers of burnings, which are considered a serious act of negligence on the environment. In addition to the burning of the Cerrado, another type of burning occurs on the boundaries between the cerrado and the forest. These are areas principally affected by the ever increasing need to obtain new lands for agriculture. In contrast to the burnings in the Cerrado, this type of burning destroys huge masses of vegetation, compared with the burning of sedge and bushes in the cerrado. The surveys of deforestation in recent years showed that the rates of deforestation decreased in the period up to 1991, but, recently, new increases have been observed, amounting actually to the order of 13,000 km2 per year. It would be very important to establish a correlation between deforestation and burnings. The effect of the burnings on the lower atmosphere can be evaluated by the observation of ozone which is produced indirectly in the atmosphere. The ozone is produced by chemical reactions which always begin with carbon monoxide emitted directly from the burnings of open fields which burn by incomplete combustion. As the burnings occur on the surface, their effect is also observed primarily on the surface. However, the consequences of the burnings end up spreading throughout the lower atmosphere. The objective of this research is to document the distribution of gases produced by burnings, especially ozone, in the troposphere of the tropics in Brazil. This work should be carried out on areas in which the burnings are efficient, and the results should be correlated with rates of deforestation. Sporadic field campaigns were undertaken in the past, but we have still not conducted systematic observations.We propose a continuous and systematic observational campaign during two consecutive periods of the burnings. This proposal focuses on an important theme in tropical ecosystems and offers an opportunity to better understand an importante problem in tropical Brazil. (AU)