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Instituto Nacional de Pesquisas Espaciais - INPE (2015)

Susceptibilidade à degradação/desertificação no semiárido brasileiro : tendências atuais e cenários decorrentes das mudanças climáticas e do uso da terra

Rita Marcia da Silva Pinto Vieira

Titre : Susceptibilidade à degradação/desertificação no semiárido brasileiro : tendências atuais e cenários decorrentes das mudanças climáticas e do uso da terra

SUSCEPTIBILITY TO DEGRADATION/DESERTIFICATION IN THE BRAZILIAN SEMIARID : CURRENT TRENDS AND SCENARIOS RESULTING FROM CLIMATE CHANGE AND LAND USE

Auteur : Rita Marcia da Silva Pinto Vieira

Etablissement de soutenance : Instituto Nacional de Pesquisas Espaciais - INPE

Grade : Doutorado 2015

Résumé
Approximately 57% of the Brazilian northeast region is classified as semi-arid climate type. The region has been undergoing intense land use processes in the last decades, which have resulted in severe degradation of its natural assets and desertification. Therefore, the objective of this study is to identify the areas that are susceptible to desertification in this region. One of the most used methods for the analysis of desertification is the MEDALUS methodology based on Environmentally Sensitive Area index (ESAI), which has been applied and validated in various scales and resolutions in several European countries. In Brazil, several studies were developed to determine desertification indicators. For example, Crepani et al. (1996), developed a methodology based on the concept of the eco-dynamic principles, and on the relationship between morphogenesis and pedogenesis to identify areas that are susceptible to soil erosion. The present study combines both methodologies to better understand the process of desertification in semi-arid region of Brazil, Eleven indicators of desertification (pedology, geology, geomorphology, topography data, land use and land cover change, aridity index, livestock density, rural population density, fire hot spot density, human development index, conservation units), widely available in the study area, were used. To each indicator, weights ranging from 1 to 2 (representing the best and the worst conditions), representing classes indicating low, moderate and high susceptibility to desertification, were assigned. The results indicate that 94% of the Brazilian northeast region is under moderate to high susceptibility to desertification. The areas that were susceptible to soil desertification increased by approximately 4.6% (83.4 km²) from 2000 to 2010. From a climatic point of view, the humid and sub-humid areas have low vulnerability. However, when management issues associated with land use are taken into consideration, these areas become potentially susceptible to degradation. In addition, scenarios for the year 2040, to evaluate how climate and land use changes may affect the degree of susceptibility in the region, were generated. Two basic scenarios have been assessed : a pessimistic, when the area is almost completely deforested, remaining only 3% of natural vegetation ; and an optimistic, where deforestation is less intense remaining almost 16% of natural vegetation. However, the difference in the high susceptibility class between the optimistic scenario and the pessimist scenario where only 6.374 km2 (3%). The areas where the susceptibility increased for the year 2040 were located in the states of Minas Gerais, Piauí, Rio Grande do Norte and Sergipe. It was also noted increase of areas with high susceptibility in the Atlantic forest remnants due to the intensive use of these areas for agriculture. The aridity index and population density may be the factors that mostly contributed to the increase susceptibility in the north of Minas Gerais. In the states of Rio Grande do Norte and Sergipe, pedology was an indicator that contributed to the increase of susceptibility. The proposed methodology proved to be a useful, timely and cost-effective tool to identify areas that are susceptible to degradation/desertification, on the same scale and resolution, in an integrated framework.

Mots clés : desertificação ; MEDALUS ; modelagem de uso da terra ; nordeste brasileiro ; semiárido ; desertification ; land use model ; brasilian northeast ; semiarid ; Ciência do Sistema Terrestre

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