Bridging or bonding? A two-mode network study in top-down and bottom-up inter-municipal environmental collaborations in China

Inter-municipal collaborative networks can be initiated either voluntarily by local actors or mandated by superior authorities, yet little is known about how these initiation processes shape network structures. Building on the risk hypothesis, this study argues that different governance modes generate distinct risk environments, which in turn lead to divergent network configurations. Using a temporal exponential random graph model (TERGM) on two-mode network data of environmental collaboration in the Yangtze River Delta, China (2008–2020), this study examines how municipalities participate in collaborative arrangements across top-down and bottom-up settings. The results show that bottom-up networks are characterised by weak bonding configurations under higher uncertainty, whereas top-down networks are dominated by bridging structures facilitated by institutional coordination. In addition, while institutional and economic homophily promote collaboration in both settings, the effects of administrative ranking, transfer network, and problem complexity are more pronounced in bottom-up networks.