Mountain forests are multifunctional ecosystems but an efficient and sustainable forest management and land use strategy have to be based on the definition of priority functions. This could only be done if efficient knowledge and decision support systems are developed in order to identify, qualify, quantify and prioritize the different forest ecosystems services. Since 30 years now, the team Protection-Ecological Engineering -Restoration (PEER) of the Irstea regional research center of Grenoble is working on these actions for valorizing the forest rockfall protection ecosystem service in French and European rockfall mitigation and protection policies. The data and knowledge acquired through the development of innovative experimental protocols ( real size experiments) has allowed the development of effective models (1, 2 and 3D rockfall trajectories models integrating the effect of forest stands, tree biomechanical behavior model based on the discrete element method, forest resources and dendrometrical parameters mapping with LiDAR data, dendrogeomorphological analysis), silviculture guidelines and forest policies. This presentation will summarize the main milestone and results of these 30 years of research but also the scientific and applied perspectives for the future.