This indicator measures the population levels (abundance) and the current geographic ranges of rangeland-dependent plant and animal species, monitored across their known range. It is not possible to monitor the population levels and ranges of all species of animals, plants, and microorganisms, so some species must be selected for monitoring. If the selected species include keystone species and those that are sensitive to particular threats, such as overgrazing, irreversible soil erosion, or fire, and if the species are diverse with respect to their taxonomy, habitats, trophic levels, ranges, and life strategies, the indicator will have a higher likelihood of detecting trends in range ecosystems.