Cross-disciplinary thematic learning, characterized by the authenticity of situations, complexity of problems, and integration of knowledge, has an integration logic that is naturally compatible with the core attributes of comprehensiveness and practicality of geography as a discipline. It thus plays an irreplaceable role in enhancing students' key competencies in geography. Taking the school-based curriculum Jiangnan Geography Notes: Decoding Wetlands as a case study, this paper constructs an implementation path of "theme selection - backward design - task-driven learning - performance assessment" and explores how to improve students' key geographical competencies through interdisciplinary thematic learning.