Assessing the Ecological Value of Polder Landscapes Using a GIS-Based Ecosystem Service Evaluation Model: A Case Study of the Honghu Basin in the Middle Reaches of the Yangtze River in China

Polder landscapes integrate agricultural production with water, settlement, and habitat management. Assessing these functions together can inform planning in flood-prone lowlands, but land-cover maps alone cannot explain how dikes, ditches, and settlements influence ecosystem services. Using the Honghu Basin in the middle reaches of the Yangtze River, China, as a case study, we developed a GIS-based ecosystem service evaluation model combining typological interpretation, value equivalent factors, and analytic hierarchy process weighting. Eight indicators represented provisioning, regulating, supporting, and cultural dimensions. Services varied markedly across the basin, with higher integrated scores concentrated along major river networks and around administrative centers. Water supply scores were generally higher in the southeast, whereas traditional polders in the northwest combined relatively low flood-season regulation scores with distinctive waterfront landscape resources. Greater water-surface coverage did not consistently correspond to higher integrated spatial performance, suggesting that spatial configuration and connectivity merit attention alongside the area occupied by landscape elements. The findings support differentiated planning, including ditch maintenance, habitat mosaic retention, and protection of the character of waterfront settlements. Comparisons with studies from the Netherlands, Bangladesh, and the Vietnamese Mekong Delta identify potential applications and requirements for local calibration. The framework supports comparative assessment of polder landscapes and the identification of planning priorities. Further integration of hydrological monitoring, local indicator calibration, and beneficiary surveys can support the design of specific interventions.