A 3M Framework for Gross Ecosystem Product Valuation in Natural Protected Areas: Integrating Parameter Localization with Uncertainty Analysis

Natural protected areas harbor ecosystems with significant ecological functions and economic value. The scientific accounting of Gross Ecosystem Product (GEP) is therefore critical for harmonizing ecological conservation with regional development. Using China’s Xilingol Grassland National Nature Reserve as a case study, this paper develops and applies a novel “3M” GEP accounting framework, integrating the three core elements of multi-dimensional indicators, multi-source data, and multi-method adaptation. This framework was employed to systematically quantify the values of the reserve’s provisioning, regulating, and cultural ecosystem services. The results show an annual GEP of CNY 170.5229 billion for the 5835.65 km 2 reserve. Regulating services constituted the dominant share (97.77%), with climate regulation being the most significant component (CNY 160.15 billion). It is important to note that this high proportion is method-dependent, stemming from the industrial-substitution scenarios used to value non-market services. The combined contribution of provisioning and cultural services was 2.23%, representing 1.00% and 1.23%, respectively. Uncertainty analysis indicated a total error margin of ±9.3% (95% confidence interval), which is within an acceptable range for ecological accounting. The primary sources of uncertainty were data-resolution limitations, methodological choices, and regional parameter variability. These findings, corroborated by sensitivity analysis, confirm the robustness of the GEP estimate and clarify the influence of key ecological parameters on the valuation. By optimizing regional indicator adaptation, methodological localization, and multi-source data cross-validation, the proposed framework enhances the accuracy and policy relevance of ecosystem service valuation. It thus provides a methodological reference for GEP accounting and ecological asset management in other natural protected areas.