Implication of traditional gold mining and organic carbon dynamics across land-use and land-cover types in Tigray, Ethiopia

Abstract

Traditional gold mining (TGM) poses a critical threat to soil quality and carbon storage in Africa. This study investigates how TGM alters soil organic carbon (SOC), plant biomass carbon (PBC), bulk density (BD), and soil coarse fragments (CF) across slope positions, land-use/land-cover types, and soil depths in Tigray, Ethiopia. A total of 384 (192 composite and 192 undisturbed) soil samples were collected from mined and unmined counterparts, along with nested vegetation plots to estimate PBC. Data were analysed using generalized linear mixed models, correlation, and mediation analyses. Results show that TGM significantly reduces SOC stocks by 75.9% in upper-slope woodlands while significantly increasing BD and CF accumulation. The highest SOC (53.22 tons ha–1) was observed in unmined woodland foot-slope, whereas the lowest (3.48 tons ha–1) occurred in upper-slope mined farmlands. Mediation analysis revealed that 74% of SOC loss was driven by TGM-induced CF accumulation. Total organic carbon was also lower (p < 0.001) in mined woodlands (16.77 tons ha–1) than in unmined (86.72 tons ha–1) counterparts. The results demonstrate that TGM is a major driver of organic carbon depletion across dryland-ecosystems. Post-mining restoration measures, including backfilling of mined pits following natural soil horizon sequences and revegetation with native dryland species, are recommended to restore carbon functions.