]> An indicator species is any biological species that defines a trait or characteristic of the environment. For example, a species may delineate an ecoregion or indicate an environmental condition such as a disease outbreak, pollution, species competition or climate change. Indicator species can be among the most sensitive species in a region, acting as an early warning to monitoring biologists. A community is a social group of organisms sharing an environment, normally with shared interests. The incidence rate is the number of new cases per unit of person-time at risk to some disease.