Amidst the climate and ecological crisis, this thesis investigates the psychological drivers of environmental activism. Spanning five papers, it examines the interplay of identity and moral processes driving pro-environmental activism, utilising surveys, interviews, and fieldwork. Paper 1 details how expansive moral and self-concepts are associated with increased identification as environmental activists and activism. Reflecting scientists’ rising prominence in environmental movements, subsequent papers scrutinise the scientist identity’s impact on activism. Paper 2 used mixed methods with a multinational sample of 329 scientists from 41 countries to show that scientist identity content—particularly perceiving science and activism as harmonious—predicts engagement more strongly than mere strength of identification as a scientist. Viewing environmental stewardship as a scientific duty and believing objectivity remains uncompromised by activism correlated with greater activist involvement, underscoring the importance of “scientist-activist compatibilism.” Paper 3 employs critical discursive analysis to explore the ideological dilemma scientist-activists face, revealing two core strategies to reconcile traditional scientific values with the urgency of the climate crisis: redefining the scientist identity and reframing scientific work. Scientists adopt subject positions that legitimise activism, portraying it as objective, rational, and ultimately an extension of a moral duty to advocate for evidence-based solutions. Paper 4 addresses the uncertainty stemming from the climate and ecological crisis by examining how scientists construct the future along a continuum from collapse to transformation. Drawing on a critical discursive analysis, it shows how talk of an inevitable future narrows perceived solutions, while more open, transformable framings highlight human agency and invite broader strategies—from collective action to technological innovation. Paper 5 presents an ethnographic study of scientist-activists, documenting how symbols of scientific authority (notably the lab-coat) are repurposed as instruments of protest and revealing the emotional, practical, and identity-related challenges encountered at the nexus of research and civil disobedience. Collectively, these studies address the pivotal question of what motivates individuals to confront the climate and ecological crisis. The findings underscore the significance of identity and moral processes in shaping environmental activism, offering insights into the psychological dimensions of climate action and potential pathways to effect meaningful change.