Remote sensing monitoring of land damage and restoration in rare earth mining areas in 6 counties in southern Jiangxi based on multisource sequential images

Abstract

Components of the environment, such as soil and vegetation, are directly destroyed by ion-type rare earth mining processes, resulting in serious ecological problems. The destruction of land resources and ecological restoration in areas with rare earth ore have become key considerations in the sustainable development of the ion-type rare earth element industry. In this paper, ion-type rare earth ore areas in 6 counties in southern Jiangxi are taken as the research area. HJ-1B CCD and Landsat TM/OLI remote sensing data from 1995 to 2017 are used as data sources, and based on normalized difference vegetation index (NDVI) analysis and regression analysis, the statuses of rare earth element mining, land destruction and restoration in these 6 counties in southern Jiangxi are analyzed. To reduce the NDVI error related to sensor differences between different datasets, an NDVI transformation equation is constructed for the HJ-1B CCD and Landsat TM/OLI data according to a regression analysis method, and the accuracy of the transformation equation is assessed with the root mean square error (RMSE). The results show that there is a significant positive linear correlation between the NDVI data from HJ-1B CCD and those from Landsat TM/OLI; the obtained transformation equation has a high precision and can eliminate the influence of the differences in data sources on NDVI. The spatial and temporal distribution analysis of rare earth mining shows that the rare earth (RE) mining area in 6 counties in southern Jiangxi was highest in 1995, 2006 and 2017, and the total mining area was over 7 km2. The spatial distribution of RE mining is relatively dispersed, which not only increases the difficulty of supervision but also causes resource waste and, to some extent, increases the difficulty of governance. Analysis of land destruction and restoration shows that the area of land not reclaimed after mining in 1995 remains extensive, at 38.1042 km2; under the conditions of natural restoration, the restoration of rare earth ore areas is relatively slow. There is still a large area of rare earth ore that has not been reclaimed manually and requires the attention of the relevant departments to ensure its timely reclamation.