How does homophily shape environmental collaboration networks among states? Evidence from the Asia-Pacific Economic Cooperation

Global environmental challenges demand cross-border collaboration. While international organizations play a pivotal role in facilitating such collaboration, the dynamics of collaboration networks among states remain underexplored. This study investigates the formation of environmental collaboration networks within the Asia-Pacific Economic Cooperation (APEC) from 2006 to 2021, employing a Temporal Exponential Random Graph Model (TERGM) to analyze the roles of actor-based and proximity-based homophily. Key findings reveal that network density increased over time, with China and the United States emerging as central contributors, while emerging economies like Vietnam and Thailand gained more prominence in recent years. Notably, collaboration extended beyond geographical proximity, highlighting the importance of trade linkages and institutional similarity in shaping partnerships. Contrary to expectations, actor-based homophily shows limited influence, whereas proximity-based factors (e.g. trade distance and institutional distance) significantly drive collaboration. These insights advance understanding of regional environmental governance and underscore the complex interplay of homophily in fostering international collaboration.