Análise do Índice de Vegetação por Diferença Normalizada (NDVI) dos municípios de Balsas, São Raimundo das Mangabeiras e Tasso Fragoso

Abstract

Nowadays, the agricultural scenario has undergone major transformations due to the great technological advances in the field. A dilemma has arisen due to the strong presence of sustainability in order to guarantee the continuity of food production in the long term. However, various alternatives have been developed for monitoring areas in order to minimize the loss of vegetation and optimize the use of resources while keeping the area productive. Remote sensing has become a widely used tool for observing objects on the earth's surface that you want to study. Thus, NDVI has been shown to be an effective mathematical method for analyzing land use and occupation, analyzing the differences suffered by the earth's surface in a historical series and making it possible to identify plant health through radiance, aiding decision-making and increasing the precision of resource application. To analyse the Normalized Difference Vegetation Index in a historical series between 2000 and 2020 in the municipalities of Balsas, São Raimundo das Mangabeiras and Tasso Fragoso. The study was carried out in the NUGEO (Geoenvironmental Center) laboratory at the State University of Maranhão. Initially, the Landsat 5 and 8 images with their respective infrared and red bands were downloaded from the USGS website in GEOTIF format. The images were then inserted into QGIS 3.28 software for atmospheric correction and then calculated using the NDVI formula. Finally, the Kappa index was generated using a confusion matrix to check the levels of agreement between the pixels from the years evaluated. Thus, it was observed that in the municipalities of Balsas and São Raimundo das Mangabeiras there was an increase in water bodies between the years 2000 and 2020, while in Tasso Fragoso there was a 4.42% reduction in water bodies due to the greater number of bands in Landsat 8 compared to Landsat 5. As for exposed soils, there was a reduction due to the increase in sparse vegetation in the three municipalities due to the implementation of techniques such as crop rotation and fertilization contributing to the preservation of agricultural fields. Finally, dense vegetation was detected in all three municipalities in 2020, although in São Raimundo das Mangabeiras it was not possible to detect dense vegetation in 2000 and 2010, necessitating a repeat study with other indices and higher resolution images