Speaker: Sandra Díaz Abstract The functional traits of organisms are at the core of their responses to the environment and their effects on ecosystem properties. Because of this, the concept of functional trait diversity (the kind, range and relative abundance of the functional traits of the organism present in a system) is increasingly used in understanding the links between biodiversity and the various benefits that societies derive from ecosystems. Functional trait diversity has the potential to affect ecosystem services and therefore human well-being directly or indirectly through its effects on ecosystem properties that underlie them. Three main components of functional trait diversity can be identified: community weighted mean trait value, range of trait values, and trait values or species with idiosyncratic effects. The role of each of these components in determining ecosystem properties and services is expected to vary according to the local context and the service in question, and can be determined in real field situations by using a set of recently developed tools. On the other hand, these functional effect traits are related in complex ways to the functional response traits that underlie organism responses to environmental drivers. It is these functional response traits that determine decline or expansion in the face of global change. By shaping functional effect trait composition according to their perceptions and interests, different social actors directly or indirectly represent an active force shaping the functional response composition of ecosystems, and thus their vulnerability. The concept of functional trait diversity therefore provides a link between the evolution of functional traits, the provision of ecosystem services to various sectors for society, and the ways in which different social actors are shaping the biotic composition of Earth’s support systems.