Predições do uso e cobertura da terra e seus impactos na erosão do solo no ecótono Cerrado/Mata Atlântica: estudo de caso da bacia hidrográfica do Rio da Prata

Abstract

Recently, the advancement of agriculture in Brazil has caused very serious problems, such as deforestation and an increase in the amount of pesticides, erosion soil and suspended sediment that have negatively impacted the environment. Soil erosion and muddy waters in the scenic rivers of the Serra da Bodoquena National Park, especially the Rio da Prata located in central-western Brazil, have caused great concern for a region known worldwide for the transparency of its waters. Although these effects have the potential to negatively impact ecosystem services, ecotourism activities and the economic sector of municipalities in the region, no study has investigated soil erosion processes in the region. Thus, the objective of this study was to analyze the current and future impacts of land use and cover on soil erosion in the Rio da Prata basin. To map land use and land cover in the study area, we use Object Based Image Analysis (OBIA) in Landsat satellite images from the years 1986, 1999, 2007 and 2016. Future land use and land cover scenarios for the years 2033, 2050, 2080 and 2100 were created using the Cellular Automata-Markov (CA-Markov) forecasting model. The Revised Universal Soil Loss Erosion- Equation (RUSLE) associated with future land use and land cover scenarios was used to estimate soil losses for the years 1986, 1999, 2007, 2016, 2050 and 2100. The results of the simulation of changes in land use and land cover were considered satisfactory, as evidenced by the values obtained from the kappa for agreement (standard) = 0.73, kappa for no information (no) = 0.78 and kappa for grid- cell level location (location) = 0.84. Future land use and land cover scenarios indicated the advance of agriculture crop and a decrease in classes of native vegetation such as banhado, cerrado, riparian forest, seasonal semideciduous forest and wet grasslands. The results showed that there has been a decline in soil losses and sediment exports over the past 30 years (1986- 2016). Total soil loss was reduced from 10.20 million tons in 1986 to 4 million in 2016. As a result, total sediment exports decreased significantly by 69.86%, from 1 million tons to 321 thousand tons.It was found that between 1986 and 2016 a predominance of soil losses <5 Mg/ ha/year in approximately 92% of the study area, influenced by the factors topographic, erodibility and use and management. The results obtained for future soil erosion scenarios showed that between 2050 and 2100 there was a 13.84% growth in areas of soil loss> 10 Mg/ha/year. Between 2016 and 2100 the moderate, intense and extremely intense classes increased by 34.41%, 36.41% and 23.96%, respectively. The banhado (wetland) showed the lowest soil loss (0.23 Mg/ha/year). It was observed that the soil erosion rates in this class varied only 8.69%. Although the wetland region presents a low erosive potential with an annual sediment export rate with minimum values, the presence of artificial drainage channels favored concentrated flow, which enabled the development of erosive processes on the margins of some drains. The conversion of natural vegetation into agricultural land can be considered as a warning against the loss of biodiversity of fauna and flora in the region of the Bodoquena National Park, and especially in the hydrographic basin of the Rio da Prata. In addition, future soil erosion scenarios showed a 5.78% increase in the average soil erosion rate for agriculture. Therefore, with the trend of expansion of cultivated land until the year 2100, there is an urgent need for planning for soil and water conservation, which mainly aims at sustainable production and the maintenance of ecosystem services and the economic sector in the region.