Actors in the spotlight: scrutinising how actors affect strategic environmental assessment towards sustainability in municipal master plans

Changing the paradigm towards sustainability falls implicitly in transforming the urban systems, as most of the world's population lives in cities. The Strategic Environmental Assessment (SEA) process is relevant in this context because it supports the evaluation of the sustainability of the plans and promotes open and accountable decision-making. However, SEA processes are embedded in a broader decision-making context, where the different roles of the actors and their impacts on the planning process remain unclear. This study explores the contributions of the SEA actors and how they influence the outcomes of SEA towards sustainability, employing a case study research design and a content analysis on the SEA of 12 Municipal Master Plans (MMP) in Portugal. Results show that public participation tends to be weak and is only sought after all decisions have been made in the planning process. The study revealed that the SEA practitioner’s role is distanced from the MMP planning team, constraining their capacity to influence the plan development. The results highlighted the significance of initiating actors’ involvement at the beginning of the assessment process and improving the knowledge exchange between the actors. These strategies have the potential to foster collaboration, transparency, and a more integrated approach to SEA.