Limited but localized: geochemical and biodiversity impacts of shale gas extraction on soil ecosystems

The rapid global expansion of shale gas extraction has intensified scrutiny of its environmental impact, yet research on terrestrial ecosystems remains limited compared to aquatic systems. To address this gap, we investigated the Fuling shale gas field in China's Sichuan Basin-a region of intensive hydraulic fracturing activity-to evaluate effects on soil geochemistry and fauna. We quantified hydraulic fracturing-associated tracers (i.e., electrical conductivity (EC), chloride (Cl^-), strontium (Sr), and barium (Ba)) across three distance gradients (10 m, 50 m, and 100 m) from extraction well pads. While EC, Cl^-, Sr, and Ba concentrations were elevated at certain sampling sites near the extraction well pads, statistical analyses revealed no significant differences in the concentrations of these tracers across varying distance gradients. To assess ecological impacts, we integrated traditional morphological taxonomy with environmental DNA (eDNA) metabarcoding, enabling high-resolution characterization of soil fauna communities. Results indicated no significant alterations in community structure attributable to shale gas activities. A multiparameter index (MPI) synthesizing physicochemical and biological data further confirmed no measurable degradation of soil health. These findings suggest that current extraction practices in the Sichuan Basin have not yet caused serious soil contamination or ecological disruption within the studied spatial scope. However, as regional hydraulic fracturing intensifies, long-term monitoring of cumulative pressures and ecosystem resilience thresholds will be essential to mitigate latent risks.