Data that is observed, recorded, developed and validated in order to track changes to the quality and condition of the planet’s air, water, land and ecosystems — including their residents — on different geographic and time scales. Examples of environmental indicators include: ozone concentration in the stratosphere (to indicate the effect of chlorofluorocarbons and an increase in ultraviolet radiation), the number and diversity of organisms in a stream (to indicate whether an aquatic ecosystem is healthy).