Conflict between stakeholders about environmental and natural resources management (ENRM) issues is a significant challenge for achieving sustainable outcomes for people and the environment.Although conflict can be a constructive and important part of deliberative processes, ENRM routinely experiences dysfunctional conflict, where people involved focus on their perceived incompatibilities rather than finding solutions for the problem. This form of dysfunctional conflict leads to decision-making stagnation and exacerbation of issues which require timely management.The self-perpetuating nature of conflict means that relationships between people and groups become strained, and the potential for cooperation and compromise is undermined. In ENRM, conflict is addressed, often implicitly, through the practice of stakeholder engagement. Although advancements have been made on stakeholder engagement processes through both research and practice, conflict continues to manifest in ENRM issues.This thesis investigates ENRM conflict through analysing the contribution of ENRM stakeholder engagement practice to the prevalence of dysfunctional conflict. In order to understand the hidden complexities and drivers of conflict, the social identity approach has been applied as a theoretical lens. The social identity approach is a theoretical perspective from social psychology which explains how people become members of groups, and how groups interact. As such it is well suited to a study of ENRM conflict, where the heart of the conflict is how groups of people -stakeholders -interact with each other.First, the thesis outlines the theoretical basis for the interest in ENRM conflict, and makes a case for both why stakeholder engagement processes are a critical aspect of conflict which are worthy of investigation, and why the social identity approach is a useful theoretical lens. Following this, a theory building approach to integration of the literature across disciplines is used to present a way of understanding the human dimension of ENRM conflict, and the argument is made for the use of the social identity approach. As a result, a clear distinction is made between 'stakeholders' and 'the citizenry', where stakeholders are formalised groups with a defined interest, and the citizenry is everyone else. An integrative conceptual model for ENRM conflict is created, and is analysed with the application of the social identity approach.Next, the thesis examines the processes taken by ENRM practitioners to identify stakeholders, thereby filling a recognised gap in the literature. This is undertaken with the use of semi-structured interviews with experienced ENRM practitioners, analysed qualitatively. As a result, a typology of approaches to identification of stakeholders is presented, and the previously proposed distinction iii between stakeholders and the citizenry is shown to be reflective of how practitioners categorise people in the context of ENRM issues.The thesis then investigates a case study of a large-scale wind energy d...