In constrained environments such as mountainous and Mediterranean areas the sustainable use of forage resources by domestic herbivores has to combine production, conservation of high environmental value areas and product quality. The sustainability of animal production systems relies on their ability to reconcile economic performance based on the added value of high quality animal products and ecological performance based on the implementation of management practices relying on agro-ecological principles and allowing compensatory payments for the production of public goods. This publication is the outcome of a joint meeting of the "Mountain Pastures, Mediterranean Forage Resources (FAO/ESCORENA - CIHEAM) and Mountain Cheese" networks entitled "Forage resources and ecosystem services provided by mountain and Mediterranean grasslands and rangelands" which was organized in Clermont-Ferrand (France) from 24 to 26 June 2014. This multidisciplinary meeting aimed at sharing/contrasting viewpoints, methods and results of specialised scientists working on grassland and rangeland assessment and use. In a context of climate change and environmental concerns, livestock farming systems in Mediterranean and mountain areas share issues common to harsh environments, which can be dealt with by using similar theoretical and methodological frameworks. Cultivated or spontaneous vegetation, herbaceous or ligneous species, all forage resources should be considered together, as complementary items contributing to the multiple performances of livestock systems. More than 140 scientific contributions were presented and discussed including introductory and invited papers, short oral communications and posters. The contributions were presented by specialists from 22 different countries of mountain and mediterranean climate areas all over the world (Europe, Africa, South-America, Oceania and Asia).