UNESCO* Man and Biosphere (MAB) reserves are geographically demarcated areas all over the world where people collaborate, co-operate and work together in order to develop model-areas for sustainability. The MAB programme encourages people to take the challenge to shape model-areas for sustainability by co-work, collaboration and co-management. The emphasis with the MAB programme is to provide opportunities for people and authorities all over the world to contribute to new ways of thinking about the relationship between humans and the biosphere. To support such collaboration the participants combine the complexity of knowledge that enable them to connect natural and social knowledge frameworks, with respect to ecological, economic, cultural, and political dimensions. As with any social innovativeness, framing knowledge is a process that depends on communication. This communication concerns the interaction between humans and the biosphere and how to develop the area as a model for sustainability. One of the main goals of the MAB-programme is to share knowledge gained from experiences in the different model areas. This paper contributes to that goal by reporting on the communication processes in practice from two biosphere reserve building processes in Sweden. These communication processes introduce possibilities and constrains for the knowledge frameworks accessible to participants in the groups. The paper is based on a two-year study of two biosphere reserves and includes archival research, individual interviews and observation of group meetings. It focuses on the communication processes emerging at each site, and suggests how the practice associated with these processes may both enable and constrain future collaboration in the two groups. Although both groups strive for the emergence of knowledge frameworks to support the aim of the MAB programme, their communication practices diverge. One group approaches their mission by deliberatively, embracing consensus goals; while the other group approaches their task by agonistically, embracing pluralism. There is no best way, there are various ways of communicating within collaborations and in this strive to co-work, neither of the approaches from the examples is inherently better than the other, both introduce different possibilities and constrains as the groups move forward in modeling for sustainable futures.