Avaliação por geoprocessamento das áreas de preservação permanente hídricas, no município de Maceió, Alagoas – Brasil: uso da terra, cobertura vegetal, impactos ambientais e vulnerabilidade social

Abstract

In Brazil, the disordered use of land since colonization has caused significant changes in its original vegetation cover. Over the past fifty years, these transformations have been causing environmental impacts in areas protected by environmental legislation, such as the Permanent Preservation Areas (APPs) mentioned by the Brazilian Forest Codes of 1965 and 2012. Both codes define APPs as covered spaces or not by native vegetation, with the environmental function of preserving water resources, landscape, geological stability, biodiversity, facilitating the genetic flow of fauna and flora, protecting the soil and ensuring the well-being of human populations. These codes also define the limits of land use of properties, with respect to their existing vegetation, considering it as a good of common interest to all inhabitants of Brazil. In the last thirty years, the municipality of Maceió, located in the state of Alagoas (Brazil), has experienced a disorderly growth with violent attacks on its natural heritage, especially, its urban area. Such aggressions has caused, the emergence and proliferation of areas subject to environmental risks, some of them occurring in water APPs (marginal bands of water courses, springs and natural/artificial reservoirs). Based on these considerations, the study attempted to evaluate by geoprocessing the Water APPs of the municipality of Maceió, regarding their land use, the impacts of this use and their social vulnerability. For this, it was necessary to create a environmental digital model of the municipality of Maceió through the use of a Geographic Information System (SGI), in which geoprocessing techniques were applied by Federal University of Rio de Janeiro's (SAGA / UFRJ) Geo-Environmental Analysis System. The purpose of the use of these techniques was to map and quantify the water APPs in the municipality of Maceió, with respect to the aforementioned elements. Thus, were generated eight digital maps or information plans of the municipality of Maceió in the 1: 50,000 scale with 10 m of spatial resolution. A base map (Basic Data) and seven thematic maps (Land Use and Plant Covering, Land Use Impacts, Social Vulnerability, Water APPs, Land Use and Plant Cover in Water APPs, Land Use Impacts in Water APPs and Vulnerability Social in Water APPs). The maps were generated from Brazilian Institute of Geography and Statistics (IBGE) topographic charts, RapidEye satellite system images scenes and pertinent environmental legislation about the theme. The generated maps overlap allowed to verify the land use and the vegetal cover in the Hydric APPs, the impacts of this use and the social vulnerability. The study showed that: (a) the categories urban site (very high-moderate impact), sugar cane (low-high impact), bay-coconut (low-high impact) and field/pasture (low-moderate impact) as being the main elements of land use on the Water APPs in the municipality of Maceió, configuring a highly impacting environmental scenario; (b) social vulnerability in the Water APPs is mostly low and medium, that is, people that have considerable human capital, infrastructure and income; (c) the need for the urgency of a appropriate environmental planning to its local conditions, based on expropriation and recovery/revitalization of the Water APPs measures, together with educational campaigns focused on the importance of their maintenance, especially their vegetal cover.