Ibe Delvaux ^* Wendy Van den Broeck

• imec-smit, Vrije Universiteit Brussel, Brussel, Belgium

To address environmental issues, it is important to strengthen individuals' environmental self-identities. This research explored how environmental non-profit organisations (NPOs) use and perceive communication interventions (social norms, perceived environmental responsibility, and social comparison feedback) that could enhance the environmental social – and self-identities of their community. This is achieved by combining a quantitative content analysis of social media posts with in-depth interviews with communication managers of NPOs. It was found that descriptive social norms are the most frequently used intervention by NPOs. However, these norms can reduce personal responsibility for environmental actions, and NPOs rarely combine them with personal responsibility messages or injunctive norms, which could tackle this issue. Secondly, NPOs primarily communicate with individuals who already hold strong environmental values, aligning with literature that suggests these individuals identify strongly with the NPO's environmental message. Based on existing literature, the need for enhanced segmentation of these target audiences is emphasised, suggesting that injunctive and dynamic social norms are more suitable for their immediate community, while descriptive norms are better suited for the general public with weaker connections to the NPO. Last, NPOs emphasise their responsibility in addressing environmental issues but neglect to acknowledge governmental efforts, which could enhance the public's environmental self-identity and promote PEBs. This study provides insight into more effective NPO communication strategies, particularly through better audience segmentation and integrating different types of social norms to enhance pro-environmental identities and behaviours.