Uncertainty is an increasingly important concern when trying to manage complex systems of interrelated natural resources. Scientific knowledge or necessary information may be lacking or incomplete. Additionally, the multiple and interdependent users of those resources may diverge in defining what really is at stake. When they frame issues in very different ways, ambiguity results, i.e., the existence of two or more equally plausible interpretation possibilities. Environmental management in these conditions implies a shift in attention from solving clearly delineated problems to continuous negotiating and tuning between different actors and expertise domains. This requires dealing with the frame differences in a reciprocal way by mutually acknowledging frames and connecting them. Some or all parties will have to revise, enlarge or reframe the way they relate to the issues and to each other, in order to support mutual understanding and common action. The contribution of experts does not consist then in providing total predictability nor in predefining issues and solutions, but in supporting a joint learning and negotiation process among different actors and in feeding this process with relevant information. Behavioural simulations may play an important function to stimulate multi-actor learning and negotiation processes.