Qazvin Province is facing escalating environmental challenges, including soil contamination, severe depletion of groundwater tables, degradation of traditional orchards (Bāghistāns), and unbalanced industrial sprawl. These issues underscore the urgent need for a Strategic Environmental Assessment (SEA) of the Provincial Territorial Development Plan (approved in 2020), which serves as the primary strategic document guiding the province’s economic and spatial development.

Employing a descriptive-analytical approach, the present study applies the SEA methodology. First, through a systematic review of the literature and prior research, 14 key environmental indicators were identified and refined. These indicators were then used to assess the ten core strategies of the Qazvin Provincial Territorial Development Plan. An effects matrix technique was utilized to evaluate impact characteristics (intensity, direct/indirect nature, short/long-term duration, reversibility/irreversibility, and cumulative effects).

Results reveal that six strategies—Agriculture, Industry and Mining, Settlement, Commerce, Tourism, and Transportation—generate significant negative environmental impacts. The High-Value Services and Science & Technology strategies, while generally positive, exhibit adverse indirect and long-term effects in certain dimensions. In contrast, the Environmental and Socio-Cultural strategies display no negative impacts.

Overall interpretation of the findings indicates that the plan’s negative environmental effects outweigh its positive ones, and the mitigating measures embedded in the Environmental strategy are insufficient to offset the damage caused by other strategies. Sensitivity analysis across three scenarios confirmed the robustness of the impact prioritization for policy revision and demonstrated that implementation of the proposed corrective measures could reduce negative effects by up to 54%.

Recommended remedial strategies focus on pollution reduction (continuous monitoring, wastewater treatment, renewable energy adoption), water-demand management (tiered pricing, efficient technologies), and natural cover conservation (revival of traditional orchards). However, successful implementation will face challenges related to budgetary constraints, stakeholder resistance, and inter-organizational coordination.