Participatory modelling is one of several techniques that can help communities to share and test ideas, and to agree on the ‘best bet’ for improving livelihoods of individuals and communities. A case study from Africa illustrates how participatory modelling can help change livelihoods, by informing communities, by providing an objective way to conduct ‘risk-free’ experiments and explore scenarios, and by helping people to gain the confidence needed to make changes. This case study highlights how participatory modelling can inform communal decisions about shared rights to avoid ‘the tragedy of the commons’. The example illustrates how a shared understanding of a resource, coupled with a rigorous framework to consider its dynamics, leads to better decisions and sustainable outcomes. The resulting model is not an endpoint, but a disposable ‘stepping stone’ in developing the confidence needed for communities to take action. Thus for many participatory models, success means being momentarily inspirational in the search for solutions, rather than being a permanent monument to a static concept.