Cumulative ecological impacts of river sand mining under weak environmental governance in Indonesia

River sand and gravel extraction is a significant pressure on tropical rivers, yet links between governance and ecological outcomes are under-measured. We assessed East Lombok, Indonesia (۲۰۱۹–۲۰۲۵) with a Before-After/Control-Impact approach, combining field water quality and macroinvertebrates with Sentinel-۲ land- cover change, RUSLE erosion modeling, and a site-level Governance Intensity Index (permits, inspections, sanctions/closures, revegetation). Turbidity (۳۰–۸۰ NTU compared with ۱۰–۳۰ NTU) and TSS (۲۰–۶۰ mg/L compared with ۵–۲۰ mg/L) were elevated in mined reaches relative to upstream/control reaches, and dissolved oxygen was ۲–۳ mg/L lower during monsoon flows. Remote sensing revealed ۱۰–۲۰% riparian vegetation loss and ۱۵– ۳۰% bar expansion; RUSLE predicted a ۱۰–۲۵% increase in erosion risk at the catchment scale. Biotic responses were consistent: Shannon diversity decreased from ~۲.۰–۲.۵ to ~۱.۰–۱.۵, and EPT richness from ۸–۱۲ to ۳–۵ taxa downstream of extraction. More robust governance (higher index scores) mitigated—although not entirely—the magnitude of effect sizes for turbidity/TSS and loss of biodiversity. These results demonstrate cumulative seasonal effects that are conditioned by local governance implementation capacity, particularly enforcement consistency and post-extraction management. Existing policy instruments (licensing, riparian buffers, and post-extraction restoration) can ameliorate degradation when uniformly applied. We offer practical monitoring and management advice to help bring local governance in tropical sand-mining rivers in line with ecological protection.

کلیدواژه ها:

River Sand Mining ، Water Quality ، Macroinvertebrates ، Governance Intensity ، Environmental policy ، Indonesia Mining Law