This paper compares and contrasts the science and public perceptions of the role of forests in relation to water quantity (annual and seasonal runoff and recharge) and erosion. It is suggested that the disparity between the two perceptions needs to be addressed before we are in a position to devise and develop financing mechanisms for the conservation and protection of indigenous forests. Examples are given of three ‘interactive’ forest hydrology research programmes: in the UK, South Africa and Panama. Through the involvement of stakeholder groups, often with representatives comprising both the science and public perceptions, interactive research programmes were designed not only to derive new research findings but also to achieve better ‘ownership’ and acceptance of research findings by the stakeholders. Following this approach, a new programme of research is outlined, aimed at improving our knowledge of forest impacts on seasonal flows and which represents DFID’s contribution to the UN Year of Mountains, 2002. It is concluded that to move towards a reconciliation of the different perceptions and to connect policy with science will require further research to understand how the ‘belief’ systems underlying the science and public perceptions have evolved, and better dissemination of research findings.