Sistemas, Caos e o Processo de Desertificação no Semiárido Brasileiro: complexidade e interações.

The Systemic Thinking rose in notoriety by the first half of the XX century, around 1950, and reverberated its precepts to every field of knowledge, including Geography. We made a theoretical revision about the evolution of this concept on the scientific field, including to the Theory of Chaos, since both became complementary and important for the understanding of the inner workings of complex systems. By being a theoretical work, discussions were realized under the the research of various authors, whose works dealt with the complexity of the topic on a scientific perspective and the complexity of its interactions between social and environmental systems, as well as the desertification of the semiarid. We took as an example of complex system and object of analysis the brazilian semiarid, by elaborating discussions and attempting to illustrate this relationship through the socioambiental and spatial dynamics associated with the desertification process that has struck some areas of Brazil. The main results reveal that this system is maintained by the interrelation of various elements, which make it complex and fit to support variations/internal and external inputs that could "shake" it's structure. However, due to constant reorganizations carried out by centuries of deforestation, those human interventions have created a chaotic pattern which, if kept, may lead the entire semiarid system to a state of disintegration/collapse. [ABSTRACT FROM AUTHOR]