Making nonhumans present: a systematic review of mediation and enactment in more-than-human participatory design

As participatory design (PD) and more-than-human design increasingly intersect, scholars have argued for expanding participation beyond human actors. Yet nonhuman participation is typically mediated, raising the risk that more-than-human difference is flattened when translated into human-legible proxies. This study synthesises how nonhuman participation is configured and made consequential in more-than-human PD research. Following PRISMA guidelines, we reviewed 58 peer-reviewed studies published between 2016 and 2026, identified through systematic searches in Web of Science, Scopus, and the ACM Digital Library supplemented by expert recommendation and citation chaining. Through thematic synthesis, we show that nonhuman participation is enacted through diverse making-present mechanisms that format nonhuman voice and shape how claims become decision-relevant. Although many studies problematised translation, procedural safeguards were unevenly operationalised, revealing recurring tensions around gatekeeping, evidential authority, care labour, institutional filtering, and data governance. We argue that nonhuman participation in more-than-human PD is a political accomplishment of making-present, highlighting the need for more traceable mediation chains in reporting and accountability practice.