Key concepts relevant to understanding the links between biodiversity and ecosystem services Different facets of the biodiversity link to ecosystem services Biodiversity broadly encompasses the number, abundances, functional variety, spatial distribu-tion, and interactions of genotypes, species, populations, communities, and ecosystems. What levels of organization or components of biodiversity are likely to be most strongly linked with ecosystem services? For plant-dependent services, the local number of functional groups and total number of species (richness) can offer a crude first-order prediction for several ecosystem processes, such as productivity, and services, such as forage production. For animal-dependent services, species number and composition in mammalian communities are associated with reg-ulation of infectious disease, although the direction of this effect (amplification or dilution of disease) depends on the types and relative abundance of different vector species in the commu-nity (Ostfeld and Keesing, 2012). The equity of the abundances (evenness) of individual species is also important in relation to biological invasions. For example, reducing evenness in plant species communities can decrease resistance to invasion by exotic plants and insect herbivores (Wilsey and Polley, 2002). Theory predicts that increasing horizontal diversity (numbers of species within trophic lev-els) tends to promote several ecosystem functions that feed into ecosystem services; however, increasing vertical diversity (numbers of trophic levels) does not necessarily do so (Loreau, 2010). For plant-dependent ecosystem services, the level of service delivery probably depends most on local plant diversity because plant species interact at a local spatial scale, but there is some evidence that ecosystem services could depend on plant diversity at larger spatial scales (beta or gamma diversity; Isbell et al., 2011). The different components of ecosystem services A critical issue in ecosystem service assessments is the scant knowledge on how ecosystem services and their components (i.e. supply, delivery, use demand, value and benefits) are produced and maintained, how they are affected by system changes, such as land use change, and how they depend on different levels of biodiversity. To improve this knowledge, we distinguish between ecological processes (called 'supporting services' in the Millennium Ecosystem Assessment; MA, 2005) and 'functions' that produce ecosystem services. Func-tions are intermediate products; they are necessary to the production of services but are not services themselves, i.e., not used or acknowledged directly by a beneficiary. These interme-diate products or processes often underpin or determine the potential service production or supply, which can benefit society. The delivery of a service arises from the interaction between its supply and the demand from stakeholders who benefit from it (Tallis et al., 2012). The benefit and value of a service reflect how people assign importance to the ser-vice, which can be evaluated in terms of market value or from a cultural perspective. For example, primary production (an ecosystem process) is needed to maintain abundance of fish population (the service supply), which can be harvested to provide food (delivery) and high nutritional value (benefit). As another example, nutrient cycling (process) is needed for water purification (supply) to provide clean water (delivery) for domestic use (benefit) (Raffaelli, 2016; Jax, 2016a).