Dinâmica da fragmentação florestal na região metropolitana de Santarém, sob perspectiva da lei florestal brasileira

Abstract

Fragmentation is one of the main factors of forest degradation and, in order to contribute to understanding the results of human actions in the Amazon, this study aimed to analyze the fragmentation of vegetation in part of the metropolitan region of Santarém, from the perspective of the Brazilian Forest Law. With this, the selection of images of the land cover and land use classification of the MapBiomas project (Collection 9), from the years 1993, 1998, 2003, 2008, 2013, 2018 and 2023, was carried out. All geoprocessing procedures were performed in the QGIS 3.22 Biatowieza LTR software and complements, and the results were analyzed through the Excel software. The selected images were regrouped into the following classes: forest, herbaceous and shrubby vegetation, agriculture, non-vegetated area and water body, from which the landscape metrics were calculated: Land Cover (ha), Landscape proportion (%) and Number of patches (fragments). The data of the forest class were vectorized and organized into 3 size classes, from 0.09-25.00 ha, 25.01-100.00 ha and greater than 100.01 ha, up to the size of the largest fragment. Finally, a map of changes in land cover and use was prepared between the years 2008 and 2023, classifying the study area, according to the parameters of the Forest Law. The results showed that deforestation in 30 years was 189,384.30 ha, while the increase in agricultural activity was 190,863.63 ha, with soybean cultivation in the oldest occupations and livestock in the most recent occupations, a process that favored the reduction of traditional agriculture and regional biodiversity. Forest fragmentation showed a growth of ~172% in 30 years, and between 2018 and 2023, fragmentation was ~83%. Of the total fragments in 2023, ~97%, were smaller than 100 ha, that is, more susceptible to the negative effects of fragmentation, concentrated in older occupations, possibly composing areas of legal reserve and/or permanent preservation, with little capacity to provide environmental services. These results indicate that landscape patterns were determined by agriculture and cattle raising and point to the need for actions that encourage forest restoration and reduce deforestation for the sustainability of the Amazon.