What constitutes an Element Occurrence (EO) for a given species?
One can consider an occurrence as being analogous to a population (more or less a group of non-regularly-interbreeding individuals of a species in a particular geographic area). With largely immobile plants we typically use a distance of 1 km to separate occurrences. With mobile animals separation distance is much more difficult to determine. For many species (particularly those that are rare range-wide) the definition of an occurrence is defined globally by NatureServe so that all data centres define an occurrence for the same species in the same way. For species that don’t have globally defined element occurrence specifications biologists at the NHIC define an Ontario specification. The definition that NHIC uses for an occurrence is often explained in the Element Report that is now publicly available on our web site.
