Coherent responses to important problems such as climate change require involving a multitude of stakeholders in a transformative process leading to development of policy pathways. The process of coming to an agreement on policy pathways requires critical reflection on underlying system conceptualizations and commitment to building capacity in all stakeholders engaged in a social learning process. Simulation models can support such processes by providing a boundary object or negotiating artifact that allows stakeholders to deliberate through a multi-interpretable, consistent, transparent, and verifiable representation of reality. The challenge is how to structure the transdisciplinary process of involving stakeholders in simulation modeling and how to know when such a process can be labeled as transformative. There is a proliferation of approaches for this across disciplines, of which this article identifies Group Model Building, Companion Modeling, Challenge-and-Reconstruct Learning, and generic environmental modeling as the most prominent. This article systematically reviews relevant theories, terminology, principles, and methodologies across these four approaches to build a framework that can facilitate further learning. The article also provides a typology of approaches to modeling with stakeholders. It distinguishes transformative approaches that involve stakeholders from representative, instrumental and nominal forms. It is based on an extensive literature review, supported by twenty-three semi-structured interviews with participatory and non-participatory modelers. The article brings order into the abundance of conceptions of transformation, the role of simulation models in transformative change processes, the role of participation of stakeholders, and what type of approaches to modeling with stakeholders are befitting in the development of policy pathways.

Projected plastic production volumes are rising, as is societal and political attention to plastic pollution and possible health impacts. In line with ambitions for climate mitigation and the circular economy, various national and international policies and action plans address the reduction of impacts of plastics. Quantitative scenario analyses show that even if current ambitious targets to reduce plastics are achieved, plastics will remain a source of millions of tons of environmental pollution annually. To achieve a sustainable transformation of the global plastics economy, 'extraordinary effort' and 'coordinated global action' beyond current ambitions are needed. While mapping knowledge gaps for the effects of micro and nano plastics (MNP) is crucial, mapping alone is not enough to achieve the needed transition. In this communication, we propose a scope for the exploration of societal transformation pathways to safe and sustainable plastics. To see which efforts are needed globally we need to advance in the following three areas: (i) embedding risk assessment methodologies in wider cost-benefit and life cycle analyses; (ii) using safe-and-sustainable design strategies that include alternative solutions and look at multiple life cycles, and (iii) reflecting on the societal transformation pathways with stakeholders by using co-created quantitative models. We believe that these practices are crucial in the coming decade to realise the extraordinary effort of defining safe and sustainable plastics.

Interdisciplinary systems insights This study demonstrates that the success of systems modelling depends not only on model quality but also on the social conditions under which models are developed...