A causal modelling workflow for spatiotemporal ecological impact assessment with quantified counterfactual prediction...

Minimizing the ecological impacts of anthropogenic pollution on aquatic ecosystems remains a central challenge in environmental impact assessment. Advances in this field require a computational causal workflow capable of separating discharge-related effects from natural spatiotemporal variability and predicting ecosystem responses under alternative intervention scenarios. This is especially demanding in observational studies, where confounding bias can obscure ecological effects and weaken causal interpretation. This study addresses that challenge by recasting a validated causal architecture as a modular workflow for counterfactual intervention analysis. The framework links community-level ecological responses to an interconnected environmental network, tests structural sufficiency, and propagates changes in discharge-related drivers through the supported system of equations. Once spatiotemporal structure had been modelled and validated, intervention effects could be estimated along the river continuum. Intervention-based counterfactual predictions showed that reducing the relevant discharge-related drivers to one-tenth of their observed values shifted conductivity, total organic carbon, total phosphorus, nitrate, and chlorophyll a towards baseline conditions, while the downstream macroinvertebrate community no longer exhibited a detectable effluent-related shift. The magnitude of improvement across the network indicated that the framework could estimate the scale of reduction required for ecological recovery. By integrating causal model construction, structural validation, and counterfactual prediction within a single reproducible workflow, this study extends causal modelling from explanation of observed variation to quantitative appraisal of management-relevant intervention scenarios. The framework therefore provides a basis for estimating how far stressors must be reduced to achieve ecological benefit and for identifying the intervention targets most relevant to wastewater management and freshwater ecosystem protection.