Alterações de paisagem na Região do Baixo São Francisco e estratégias para a restauração ambiental

• Autor(a) principal: Torres, Maria Fernanda Oliveira
• Data de Publicação: 2022
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: https://ri.ufs.br/jspui/handle/riufs/17969
• topic: Hidrologia; Sensoriamento remoto; Ecologia das paisagens; Degradação ambiental; Paisagens; Desenvolvimento de recursos hídricos; Recharge areas; Remote sensing; Landscape ecology; River systems; Environmental degradation; Degraded areas recovery; CIENCIAS AGRARIAS

In the Lower São Francisco River, northeast of Brazil, information on the effects of constant environmental changes caused by climatic and anthropic variations is still scarce. Thus, continuous environmental monitoring is necessary to develop mitigating actions to understand geoenvironmental changes and evolutionary dynamics over time. The first study was carried out to analyze changes in land usage and occupation, changes in vegetation pattern, and landscape metrics, in a stretch of Permanent Preservation Area, in the region of Santana do São Francisco, through satellite images from Sentinel 2A. The total studied area corresponds to 596 ha, and 60% of the riparian areas are degraded. The relevant forest fragments are distant and with little or no connectivity. It makes it possible to infer the risks to genetic diversity, both locally and regionally, concerning autochthonous resources. In a second study, the geomorphological changes in the São Francisco River canal, near its mouth, were analyzed via the Modified Normalized Difference Water Index (MNDWI) and the changes in the left river bank, from 1986 to 2020. For this, Landsat 5 and 8 satellite images were used. In the studied region, the sedimented areas above the river water level occupy 10.64 km2, 22% more, considering the beginning of the evaluation (1986). The São Francisco River lost approximately 20% of its area. Rainfall and flow data present a positive correlation with MNDWI values; and negative for those of sedimentation. There was an advance of about 86.36m into the river, for each transect. In a third study, the development stage of a stretch of a riparian forest area under restoration process was evaluated, after 18 years of implantation, through the analysis of the landscape and biotic and edaphic indicators. It was observed that in 2010 the restored area had 100% of the soil covered with dense vegetation. In the seed rain, the presence of 1,198 propagules, belonging to 27 different species, was observed. The seed bank presented only species of arboreal habit. In the seedling bank, 28 botanical families were recorded and 57% of the individuals belong to the arboreal-shrubby structure of the forest. There was an increase in biomass, gross primary production of CO2, and soil fertility improved over time with restoration actions, proving the reestablishment of its ecological functions. In the region, there are changes in the forest, hydrological and geomorphological levels. The São Francisco River canal responds to any environmental change. The reforestation carried out in the riparian forest area has brought benefits to the region and can serve as a model for future restoration projects. The methodology was based on the analysis of the conservation stage of the region in forest and geomorphological aspects, and it can be applied to evaluate regions with similar physiographic features.