Abstract
Remote sensing technologies can play a fundamental role in the environmental assessment of open-cast mining and the accurate quantification of mine land rehabilitation efforts. Here, we developed a systematic geographic object-based image analysis (GEOBIA) approach to map the amount of revegetated area and quantify the land use changes in open-cast mines in the Carajás region in the eastern Amazon, Brazil. Based on high-resolution satellite images from 2011 to 2015 from different sensors (GeoEye, WorldView-3 and IKONOS), we quantified forests, cangas (natural metalliferous savanna ecosystems), mine land, revegetated areas and water bodies. Based on the GEOBIA approach, threshold values were established to discriminate land cover classes using spectral bands, the normalized difference vegetation index (NDVI), normalized difference water index (NDWI) and a light detection and range sensor (LiDAR) digital terrain model and slope map. The overall accuracy was higher than 90%, and the kappa indices varied between 0.82 and 0.88. During the observation period, the mining complex expanded, which led to the conversion of canga and forest vegetation to mine land. At the same time, the amount of revegetated area increased. Thus, we conclude that our approach is capable of providing consistent information regarding land cover changes in mines, with a special focus on the amount of revegetation necessary to fulfill environmental liabilities.
Highlights
The societal and environmental impacts of mining activities have become a great focus of public interest [1]
Our classification permitted the mapping of land cover and open-cast mine changes in the N4-N5 mining complex with sufficient accuracy
The remote sensing of mine land revegetation dynamics was able to monitor the occurrence of revegetation activities and the attendance of the mitigation hierarchy as required by national environmental laws
Summary
The societal and environmental impacts of mining activities have become a great focus of public interest [1]. The exploitation of mineral reserves should be embedded in efficient and responsible management plans that have a strong focus on the development of neighboring communities and sustainable land use. This balancing act has led to the emergence of environmental regulations in many countries, including Brazil [2], and a series of self-commitments by the mining industry [3,4]. The transformation of natural ecosystems during open-cast mining reduces the amount of wildlife habitat and endangers populations of rare, endemic or threatened species [5,6] To reduce these environmental changes, the mitigation hierarchy offers a useful form of guidance [7,8]. The four pillars of the mitigation hierarchy process increase environmental sustainability by avoiding net losses or generating positive impacts [10,11] as well as by increasing social acceptance of mining [12]
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