Scientific expertise and outcomes often give rise to controversy. An educational response that equips students to take part in such discussions is the teaching of socially acute questions (SAQs). With SAQs, the understanding of uncertainty, risk and how knowledge is developed is central. This study explores the way in which students from different disciplines and different continents are brought together via a digital platform to explore SAQs about environmental issues (a green algae outbreak linked to release of fertilisers along the coast of Brittany; the construction of a desalination plant near Melbourne to produce freshwater; and changes in meat consumption on a global scale, with regard to population projections in 2050). We have developed frameworks for looking at the quality of the collective reasoning and at the nature of students' interactions, so that we can analyse the organisation of the learning communities and the building of collegial expertise. The results show that interdisciplinary discussions, especially on an international scale, foster the understanding of complex situations. In this paper, we discuss the modalities of one didactic scenario to enhance critical thinking and collaborative work, and to provide space for learners to support argumentation.