Mudanças na paisagem com a transposição do Rio São Francisco, no domínio Caatinga, Pernambuco

Abstract

The Domain Caatinga has been dealing, for decades, with negative anthropic actions on its natural resources. Among the current socioeconomic activities, which has generated controversy in relation to the conservation of the Caatinga domain, is the Project of Integration of the São Francisco River with the Hydrographic Basins of the Septentrional Northeast (PISF), which aims to fill the water deficit in the semi-arid regions of the Northeast. In order to analyze the interaction of this enterprise with domain Caatinga, this study aims to evaluate the dynamics of change in land use and forest cover in the Directly Affected Areas (DAAs) by the by the Project of Integration of the São Francisco River with the Hydrographic Basins of the Septentrional Northeast, from the portion of the East Axis located in the State of Pernambuco, Brazil, for a period of 20 years. For that, TM / Landsat 5 and OLI / Landsat 8 images were used, referring to the years 1998, 2008 and 2018, periods before, during and after the transposition, respectively. The spectral bands chosen for the analysis of land use and cover were 5, 4 and 3, generated by the Thematic Mapper (TM) sensor, and bands 6, 5 and 4, produced by the Operational Land Imager (OLI) sensor, each set of bands refers, respectively, to short-wave infrared, Near Infrared e red. Image processing and classification were performed using the QGIS program, using the Semi-Automatic Classification Plugin (SCP) complement, which used the Maximum likelihood algorithm in the image classification process. The land use and land cover classes used in this analysis were savanna-steppe, savanna-steppe, anthropized and / or uncovered area, water resources and agricultural area, which were quantified both for the DAA area of PISF and its portions in the affected municipalities. Regarding verification and validation of the data obtained and resulting from the supervised classification, accuracy was obtained using the Kappa index. To quantify the classes of use, applications of mathematical operations of the GIS were made. Also, studies related to the landscape structure were carried out, using different types of metrics, processed in the Patch Analyst tool, an extension of ArcGIS 10.5. As a result of the analysis of the 20 years, it was obtained that the savanna-steppe vegetation cover showed a 13.86% reduction. However, there were additions in the areas of ciliary savanna, water resources, agricultural area and anthropized area in 1.93%, 0.11%, 0.31% and 11.51%, respectively. The municipality most affected by the transposition works was Floresta, which encompasses 39.36% of the Directly Affected Area in its territory. The forest fragmentation present in the studied area, after the age of 20, was expressed by the reduction of large fragments (26,389.18 ha) and increase of small (2,837.07 ha) and medium (798.03 ha). In relation to the savanna-steppe ciliary, it presented oscillation in the size of its fragments, due to climatic variations and human interventions. The reduction in the size of the fragments contributed negatively to the central areas, as it favored the edge effect.