A measure of the variety of organisms within a level of biological organization at any scale in a defined place. Types of biodiversity include genetic diversity; species diversity; guild, feeding group, or functional group diversity; habitat or biotope diversity; and any other measure of biological variety at a location. Biodiversity can be evaluated at levels of biological organization including taxonomic groups (for example, fishes), communities (for example, megafauna), habitats (for example, soft substrate, coral reef), or ecological systems (for example, number of habitats or biotopes in a managed embayment) and at spatial scales ranging from submeter to global. Biodiversity is widely viewed as critical to ecological functions, services, and economic benefits; changes in biodiversity have been closely linked to changes in the ways ecosystems function. Biodiversity is usually considered as an inherent ecosystem service. For purposes of marine planning, biodiversity measures that can be compared across the planning area are most valuable in decision-making. Distributions include quantifications of numbers of species, genetic types, taxonomic groups (for example, fishes), communities, or habitats at a place; diversity indices that can include rarity or relative abundance of types; measurements of proxies (for example, habitat types with known high or low numbers of species); or models. Assessments can estimate, value, monetize, or model the ecological function or service values and impacts of various aspects of biodiversity; identify biodiversity hotspots; or evaluate the effects of pollution, development, climate change, or other stressors on biodiversity. Predictions are the results of models or projections of future distributions, values, or impacts to biodiversity, including future changes produced by natural and human processes. Predictive models can also evaluate the ecosystem effects and ecological function or service impacts of altered biodiversity; scenario-testing models can compare ecological function or service outcomes of different management actions that affect biodiversity.