In ancient times, before the emergence of man, the burning in savanna environments was caused primarily by lightning. With the dominance of the use of fire and the great growth of their populations, man began to increase the frequency of burnings in these environments, as well as changing the time of occurrence of natural burns.
Available information reveals that the use of fire was widespread among all indigenous groups that inhabited the cerrados. Through fire, they manipulated the environment and benefited in various ways: they encouraged flowering and fruiting of plants that were useful to them, attracted and hunted animals that came to eat the herbaceous stratum regrowth, frightened off unwanted animals - like snakes -, they got rid of some pests (insects, mites), “cleaned up” areas to set up their villages and crops, and used fire for signage and religious rituals.
Indians had a great knowledge of the effects that burns at different times of the year, or of different intensities, or at different annual frequencies, could have on each group of plants or animals. For example, they knew that if they burned the Cerrado every year, they could harm tree species, killing young individuals, but that by burning every 2-3 years they stimulated the fruiting of trees and gave young people time to develop mechanisms. defense against fire (like thick cork); usually burned the Cerrado in the dry season, shortly after the pequizeiro (Caryocar brasiliense) launch their shoots (August / September), so as not to damage their flowering and fruit production, which begin in October after the first summer rains.
The way to specify the most suitable time to burn was through some indicator species (those of interest), such as pequi, whose fruit was widely used as a food and medicinal resource. On a more refined time scale, they were also guided by cloud formation, river level, or the behavior of some animals to know when to best enjoy the effects of fire. In general, they burned small areas, or larger areas in a mosaic system, interspersed with burned and unburned sites, which served as a refuge for more fire-sensitive plant and wildlife species.
Part of this knowledge was passed on to farmers and ranchers, but unlike the Indians, their sedentary lifestyle did not allow them to maintain the tiled burning system, nor wait a few years to re-burn the same place as they needed to maximize, temporal. and spatially, the benefits of fire. This resulted in an increase in the frequency and extent of burned areas, often causing environmental degradation in terms of land depletion, erosion, stratum exclusion, extinction of native species, infestation by ruderal species, among others.
Yet, misuse of fire does not negate the benefits that its use may bring. In savannas, fire is a precious management tool that can lead to a wide range of ecological outcomes over the medium term. Dealing with the elements that make up the burn regime - frequency, intensity and time of burning - can increase or decrease the production of leaves and fruits, stimulate or exclude certain species of plants and animals, increase or decrease the nutrients available to plants. on the ground, thinning or thickening the tree vegetation. Thus, the appropriate and planned use of fire can be a good and inexpensive management strategy for the maintenance of natural pastures as well as national parks and biological reserves intended to protect the Cerrado ecosystems.
The aversion to fire that is now seen in environmental agencies and the media comes from misleading information that confuses valid concepts for tropical forests with the Cerrado's functioning and dynamics, completely different things. It is a shame, because a good understanding of the role of fire and its effects on Cerrado ecosystems, acquired through the combination of technical-scientific knowledge generated by researchers and the accumulated empirical knowledge of the Cerrado inhabitants, would allow the proper application of this tool. , with good results for the solution of several problems that today reach the natural and semi-natural cerrados.
Text by Vânia R. Pivello, prof. from the Department of Ecology
from the Institute of Biosciences of the University of São Paulo