Mapping and Analysis of Geodiversity Indices in the Xingu River Basin, Amazonia, Brazil

Abstract

From the 1990s, geodiversity studies have been widely carried out in order to understand, describe and preserve the natural heritage of the abiotic environment. Geodiversity assessments have principally been conducted using geological (minerals, rocks and fossils), geomorphological (landforms and processes) and pedological variables. This concept has been widespread and consolidated in scientific circles, where early studies focused on methods that assessed the spatial variability of the geodiversity, with a particular focus on quantitative aspects. In this study, a geodiversity quantification methodology (Pereira et al. 2013) has been applied to the Xingu River basin (Amazônia, Brazil), which covers approximately 51 million hectares. This methodology is based on measuring and integrating abiotic elements, which are spatialised using thematic maps at scales varying between 1:250,000 and 1:1,000,000 and using a 1:25,000 systematic linkage grid. This methodology was adapted for the Amazonian environment by including parameters related to river channel patterns, as approximately 12.6 % of the area is a fluvial environment (channels and floodplains). After applying the methodology, geodiversity indices varying between 4 and 32 were obtained, and a geodiversity hot spot in the basin was identified in the region known as “Volta Grande do Xingu” (The Great Bend of the Xingu). The results of the study highlight the fragility of legal tools for environmental protection of the area, primarily those related to aspects of the physical environment. Although large portions of the basin are partially or fully protected (as indigenous lands and conservation units), the area with the greatest geodiversity is precisely the one which has fewer legal protection devices and is where the Belo Monte hydroelectric power plant is being built.