At the regional scale, the complexity of ecological deterioration limits effective decision-making and preventive measures. In this study, an adverse outcome pathway approach was developed and applied to land resource management and environmental decision-making in Daye, a traditional mining city in China. First, adverse outcome pathways for land degradation were hypothesized. Second, a weight of evidence approach was used based on the data strength and causal chain strength of each degradation pathway. Then, the technique for order preference by similarity to an ideal solution (TOPSIS) was used with entropy information and integrated with the geographic information system (GIS) to evaluate the credibility of each pathway. The most likely adverse outcome pathway and the spatial distribution for different sub-regions were obtained. The apparent spatial heterogeneity suggests that land degradation pathways are closely associated with economic production activities in each sub-region. This study is expected to facilitate the identification of key mechanisms underlying ecological degradation and to guide the management of land systems to ensure long-term functioning.