The Dongting Lake Region is a major river-connected lacustrine ecosystem and ecological security barrier in the middle Yangtze River Basin, where land use change has important implications for ecosystem service provision. However, how land use transition pathways and spatial clustering jointly shape land-cover-based ecosystem service value (ESV) estimates remains insufficiently understood, particularly under a coefficient-based valuation framework. This study used land-use data for 2005, 2010, 2015, 2020, and 2025 (with the 2025 layer being not fully observation-based but derived from remote-sensing interpretation and model-assisted updating rather than direct field observations). The analytical framework integrated land-use transition analysis, land-use dynamic degree analysis, equivalent-factor-based ESV estimation, spatial autocorrelation analysis, one-way parametric sensitivity analysis with a ±50% variation, and stage-specific comparisons aligned with policy implementation timelines. These methods were applied to investigate the spatiotemporal dynamics of estimated ESV in the Dongting Lake Region. Cropland, forestland, and water bodies remained the dominant land use types, while built-up land expanded through the conversion of agricultural and ecological land. Estimated total ESV declined during the study period, although the annual rate of decline was lower during 2015–2025 than during 2005–2015. Under the adopted equivalent-factor framework, water-body-related transitions contributed most to estimated ESV change, reflecting both the ecological importance of water-related systems and the high coefficients assigned to water bodies, especially for hydrological regulation. Estimated ESV showed persistent positive spatial autocorrelation, with High–High clusters concentrated around East Dongting Lake, South Dongting Lake, and West Dongting Lake. These findings provide land-cover-based evidence for territorial spatial optimization and SDG-related ecosystem management. However, the identified clusters should be interpreted as candidate lake-centered high-value ecological spaces for further assessment, rather than as definitive conservation priorities or ecological zoning boundaries.