Aplicação e comparação de metodologias de Fragilidade Ambiental para o município de Pelotas/RS

Abstract

Excessive exploitation of natural resources has been developing several processes of environmental degradation, highlighting soil erosion. The methodological models of environmental fragility analysis have emerged to help identification of areas susceptible to occurrence of erosive processes and to assist in territorial and environmental planning. In this sense, the present paper had as objective to apply and to compare two methodologies of analysis of the environmental fragility consecrated in the literature, Ross’s (1994) and Crepani’s et al. (2001), which, based on the concept of Ecodynamic Units proposed by Tricart (1977), approach the environment from a systemic perspective. The area of study is the municipality of Pelotas, located in the southern portion of the state of Rio Grande do Sul, between the geographic coordinates 31° 50’ 6” to 31° 16’ 55” south latitude and 51° 57’ 33” to 52° 40’ 24” west longitude. For the elaboration of the digital database and cartographic documents, remote sensing data and computational geoprocessing tools were used. The environmental fragility synthesis mappings presented divergent results due to the differences in the operationalization of the methods, in the variables used and in the weights assigned to each of the variables involved. In the mapping developed using Ross’s methodology (1994), five fragility classes were identified: areas with very weak fragility (0.85%), weak (23.36%), medium (44.02%), strong (19.43%) and very strong (2.68%). In the mapping generated from the application of the methodological model suggested by Crepani et al. (2001), three vulnerability classes were identified: areas with moderately stable vulnerability (6.14%), fairly stable/vulnerable (50.04%) and moderately vulnerable (34.16%).No classes of stable and vulnerable areas were identified. In the overlapping of the synthesis mappings and comparison between classes of same hierarchical level, 5.06% of the area showed a weak fragility degree and a moderately stable degree of vulnerability, 25.62% of the area of medium fragility and degree of vulnerability moderately stable/vulnerable and 0.49% of the area degree of strong fragility and degree moderately vulnerable to soil loss. The comparative analysis of the two models of fragility, besides pointing out areas of greater fragility in the study area, will be able to mark future discussions on the formulation of a methodological proposal more adequate to the regional environmental realities.