Black sand mining can increase the frequency and the magnitude of land subsidence, which makes local communities particularly vulnerable to seasonal typhoons, climate change, and sea level rise. The aim of this research is to use satellite imagery to measure the scope of illegal black sand mining and associated environmental impacts. In the Philippines, magnetite naturally occurs in black sand in rivers and along much of the coast, and is extracted through sand mining and processing. For this study, researchers inspected satellite images of areas suspected of mining activity. Using the coordinates of identified mining sites, they analyzed the magnitude of ground displacement as a measure of land subsidence using InSAR (Interferometric Synthetic Aperture Radar) and calculated the approximate time for these sites to be submerged below sea level. Out of the 20 sites surveyed, InSAR also revealed subsidence in 6 additional sites not previously identified as mining sites, showing that InSAR is a good complement to other methods of identifying illegal mining sites.
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