Payments may be diverted to specific persons or areas to support political or other objectives. It is therefore important to define transparent principles and criteria for eligibility for payment that are publicized and defensible from a biogeographic standpoint, rather than based on political considerations. Communication media such as radio and television, as well as local institutions, including government and NGOs, as demonstrated by Viet Nam's experience, are valuable communication channels. The growing numbers of PES programmes in the region are also valuable resource on which to draw understandings and exemplify applications. Therefore, the confidence that their investment will pay off is very important to ensuring the sustainability of PES programmes.