The impact of urbanization on the interactions among the sustainable development goals: dynamic evolution and nonlinear changes in underdeveloped mountainous areas

As a global process, urbanization profoundly influences the achievement of the Sustainable Development Goals (SDGs). However, identifying how the trade-offs and synergies among the SDGs change at different stages of urbanization remains an urgent research challenge. This study focuses on underdeveloped mountainous areas, selecting Lincang City—China’s Sustainable Development Agenda Innovation Demonstration Zone—as a representative case. Based on multi-source data, this study employs Social Network Analysis (SNA) and Generalized Additive Model (GAM) to explore the impact of urbanization on the trade-offs and synergies among the SDGs. The results showed that: (1) Urbanization exerted a dual effect on SDG relationships, fostered synergies among certain goals (e.g., SDG3, SDG6, and SDG17), and transformed some synergies into trade-offs (e.g., SDG7 and SDG13). (2) The coupling among the SDGs displayed a dynamic pattern of “initial strengthening followed by weakening” as urbanization advanced. (3) SDGs exhibited varying clustering patterns at different stages of urbanization, shifted from three clusters at lower levels to two at middle levels, and eventually formed a new coupling pattern at higher levels. This study constructs and applies a localized SDGs indicator system to reveal the nonlinear evolution of interactions among the SDGs during the urbanization process, offering a novel perspective for understanding their dynamic coupling in the development of mountainous cities. It also provides scientific support for optimizing synergy pathways and advancing sustainable development in underdeveloped mountainous areas.