O processo de desertificação nos municípios de Cabaceiras e Barra de São Miguel-PB: uma análise a partir dos índices biofísicos (NDVI, TGSI e albedo) e socioeconômicos no período de 1989 a 2010.

Abstract

The desertification process is a major threat to ecological and socioeconomic systems throughout the world. The impacts caused by this process have been increasing due to the misuse of land. The objective of this study was to analyze the evolution of the land desertification process in the municipalities of Cabaceiras and Barra de São Miguel-PB, based on social, economic and environmental indicators and their relationship with local development in the period 1989-2010, through Of the dynamic space of biophysical and climatic aspects. In order to evaluate the change in soil cover and the desertification process, the relationship between NDVI (Normalized Difference vegetation Index), TGSI (Topsoil Grain Size Index) and α (albedo) of the terrestrial surface was studied. The TGSI is an index that assesses soil texture, was used in Inner Mongolia of Chima and Southern Iraq in degraded areas. For this reason, this paper sought to adapt it to regions of the Brazilian semi-arid region. In this work, soil physical analysis was performed to validate the results obtained by the TGSI. From the decision trees (DA) adapted for the wet and dry periods, maps of risks to the desertification process were generated. The analyzes showed that the values of these indices are influenced by the seasonality of the vegetation. Precipitation data were used for the variables: rainfall and dryness index for the municipality of Cabaceiras-PB. The results showed a positive tendency for rainfall and negative for the dryness index. Regarding water erosion, it has been considered the most important environmental problem caused by intense rainfall events. The potential of rainfall to generate soil erosion is known as rainfall erosivity and its estimation is fundamental for understanding the climatic aspects of a region. The rain erosivity index (EI30) was estimated by the R factor of the Universal Soil Loss Equation (USLE). The results indicated an average annual erosivity of 5,733.1 MJ mm ha-1 h-1 (Cabaceiras) and 3,222 MJ mm ha-1 h-1 (Barra de São Miguel), which, according to the conversion, corresponds to a loss Of soil of 584.4 tm mm ha-1 year -1 318.3 tm mm ha-1 year -1 respectively. The erosivity index is highly correlated with the coefficient of rainfall (Rc), R2 = 0.98 and R2 = 0.97, which allows a good adjustment of the equation. The highest values of erosivity occurred in the months of January to March, and in Cabaceiras the values extended until May. In relation to the map generated from erosion risk, it was observed that the degree of risk in most of the studied areas (82.1%) was very low to low risk, 16.7% medium risk and only 0.1% of high risk. For the socioeconomic evaluation, the statistical data made available by agencies such as IBGE (Intituto Brasileiro de Geografia e Estatística), UNDP (Programa das Nações Unidas para o Desenvolvimento), IPEA (Instituto de Pesquisa Econômica Aplicada) and the IDEB (Índice de Desenvolvimento da Educação Básica). The results pointed to weaknesses in subsistence production due to climatic conditions, low schooling, high percentage of people vulnerable to poverty, concentration of land and degradation of natural resources. Under these conditions it can be said that the desertification process is not climatic but anthropogenic.