| 12 Nov 2025
Global Surface Mining and Land Reclamation of Time Series from 1985–2022
Abstract. Surface mining has profound impacts on ecosystems, contributing to land degradation, vegetation loss, pollution, and threats to biodiversity. Given the rapidly rising demand for raw materials, understanding the dynamics of mining and reclamation processes is essential to support sustainable development. Here, we integrate and analyze a large set of mines distributed worldwide based on their known land extent circa year 2020. We integrated time-series data of the Normalized Difference Vegetation Index (NDVI), nighttime light (NTL) intensity, and land use to detect and identify changes within mine sites from 1985 to 2022 and assess spatiotemporal trajectories of mining and reclamation processes. The dataset comprises 74,726 polygons, covering a total area of 82,552 km2. Our dataset obtained the maximum potential mining disturbance boundary – the cumulative outer envelope of mining-induced land disturbance over the study period. China leads in both the number and the areal extent of mining sites, followed by the United States and Australia. Within the analyzed set of polygons, mining land footprint expanded steadily between 1985 and 2022, with the annual disturbed area peaking at 1,943 km2 in 2015, with a slowing expansion after 2015. From 1985 to 2022, the cumulative area of land converted to mine reached 40,596 km2, accounting for 49 % of the total surface mining area in our set, while the reclaimed area was 29,285 km2. Active mining areas dominated the global mining landscape, comprising 31.6 % of all polygons, with approximately 48.9 % concentrated in Asia. The spatiotemporal processes and patterns revealed in this study provide crucial insights into the development of mine sites and provide new data to support ecological impact assessments and sustainable development research in global mining regions.
The manuscript presents a dataset that extends the temporal understanding of global mining activities. The integration of multiple datasets and the long-term time series analysis (1985-2022) provides significant insights into the dynamics of land disturbance and reclamation. However, there are several critical issues regarding the definition of key concepts, the classification of mine status, visualization, and comparative analysis that need to be addressed to enhance the scientific rigor and clarity of the study.
1. Clarification and Discussion on "Undefined Mines"
The classification of mining activity status is a core contribution of this study. However, the "Undefined Mines" category requires further revision. Currently, "Undefined Mines" seems to be defined largely by exclusion (i.e., mines that do not fit into "Active" or "Closed" categories based on the MK trend test). This definition is insufficient for a scientific classification system. Authors should provide a positive definition. In addition, the results indicate that 48.9% of the mining polygons are classified as "Undefined." This is a remarkably high proportion, covering nearly half of the dataset. Such a high percentage of "undefined" results undermines the classification model's utility. The authors must discuss why this percentage is so high.
2. Distinctions between Reclamation, Revegetation, and Greening
The manuscript uses the term "Reclamation" extensively, but the methodology relies on remote sensing indices (BSP and NDVI). There is a conceptual gap that needs to be bridged. The authors should explicitly differentiate between "Greening" (increase in vegetation index), "Revegetation" (establishment of plant cover), and "Reclamation" (restoration of ecosystem function and land capability).
3. The x-axis labels in Figure 6(a) (Year) are currently stacked and overlapping, making them unreadable.
4. The manuscript lacks comparison with more recent and regionally focused high-resolution products. The authors should compare their findings with the recent study on tropical mining expansion: Sepin, P., Vashold, L. & Kuschnig, N. Mapping mining areas in the tropics from 2016 to 2024. Nat Sustain 8, 1400–1407 (2025). https://doi.org/10.1038/s41893-025-01668-9