Análise espaço-temporal da cobertura e uso da terra na Bacia Hidrográfica do Rio Formoso, Tocantins

Abstract

The present study aimed to understand the process of change in land use and land cover in the Rio Formoso River Basin (BHRF), its relationship with the territorial planning proposed in the Watershed Plan (PBH-Formoso) and its environmental implications. For this, data from the coverage and use mapping provided by the 5th Collection of Mapbiomas (2020), between the years 2007 to 2019, the Base Cart of the state of Tocantins and the Rio Formoso Watershed Plan were used. The method consisted of quantifying the thematic classes, performing the annual transition through ArcGIS software, analysis using the Cross Tabulation Matrix proposed by Poncius-Jr et al. (2004), and comparison with the environmental zoning established in the Watershed Plan and the total limit of the study area. Nine classes of land cover and use were identified, namely: savanna formation, pasture, forest formation, soybean, grassland formation, temporary crops, water bodies, non-vegetated areas and urban infrastructure, cited in order of greatest contribution to the BHRF landscape. There was a total decrease in natural areas (grassland, forest and savanna), where only the forest formation shows a subtle recovery from the year 2018, and an increase in agricultural areas (pasture, temporary crops and soybeans). On average, annually, about 3.04% of the total area of the basin undergoes some type of alteration and 96.96% shows persistence of coverage and use. In the general context, the classes of pasture and savanna are the ones that most convert and are converted into other uses, demonstrating their intermediate role in the context of the basin. The grassland and forest formations were the ones that proportionally lost the most areas, demonstrating relative passivity, while the temporary crops and soybean cultivation are the main beneficiaries, playing an active role in the transformation of the environment, while the other classes participated little in the process. In the internal context of the agricultural classes, between 2007 and 2013, the pasture areas were mostly converted to temporary crops, so that from 2013 to 2019, the main beneficiary became the cultivation of soybeans, demonstrating the prevalence of this specific crop in the region, emphasizing that its main growth is due to this aspect, with little expressive increase over natural areas. Regarding natural areas, the marked conversion of forested areas into savannas suggests a possible impact of the hydrogeological and climatic context on the growth of species that are more resistant to water deficit. The zoning established in PBH- Formoso had little influence on the transition process, since in areas of high agricultural use there was quantitative maintenance of natural areas and in protection zones, these areas were reduced. Thus, it is suggested to review the PBH-Formoso that includes environmental zoning that takes into account pre-existing uses and their behavior, the definition of areas of environmental interest based on ecological diversity and propensity to recharge aquifers, institution of mechanisms that consider the power relationship between actors and their effective participation in the decision-making process to reconcile conflicts.