Holding the ground. Alliances and defiances between scientists, policy-makers and civil society in the development of a voluntary initiative, the "4 per 1000: Soils for food security and climate".

• The role of scientists in the design of a multistakeholder partnership, the "4 per 1000″ initiative, is analysed. • The involvement of soil scientists leads to keep discussions at a technical level while the initial ambition was political. • The technical focus reinforces the credibility of the initiative but leads some civil society organisations to stay outside. • The case study leads to support the idea of accountability as an integral part of scientific engagement in the policy process. The proliferation of multistakeholder initiatives is deemed to be a key vehicle for the implementation of international agreements for sustainable development. This is the case with the "4 per 1000: Soils for Food Security and Climate" initiative (4PM), launched in March 2015 by French Minister Stéphane Le Foll, whose aim is to increase soil organic carbon (SOC) stocks worldwide, in order to simultaneously address climate change mitigation, adaptation, and food security issues. This paper explores the knowledge dynamics at play and the role scientists played in the early development of the initiative. It shows that the strong involvement of soil scientists in the design of 4 PM, as well as in the enrolment of other stakeholders, has had a dual consequence. On the one hand, it has reinforced the initiative's credibility by keeping most discussions at a mere technical level, considering soil organic carbon sequestration as the main (if not the sole) proxy for climate change mitigation, adaptation and food security. On the other hand, this technical approach has led the initiative to be hardly able to enrol representatives from peasant and familial agricultures, who have criticized the absence of clear definitions of the type of agricultural models the 4 PM intends to promote. We show that this has had detrimental consequences on the results of the 4 PM initiative, and we discuss the implications both for the framing of voluntary multistakeholder initiatives and for the engagement of scientists in such settings, notably in terms of their accountability. [ABSTRACT FROM AUTHOR]