introduction - Pennsylvania Natural Heritage Program

APPENDIX V cGLOBAL AND STATE RANKINGGlobal and State Ranking is a system utilized by the network of 50 state natural heritageprograms in the United States. Although similar to the federal and state status designations, theranking scheme allows the use of one comparative system to "rank" all species in a relativeformat. Unlike state or federal status designation guidelines, the heritage ranking procedures arealso applied to natural community resources. Global ranks consider the imperilment of a speciesor community throughout its range, while state ranks provide the same assessment within eachstate. Although there is only one global rank used by the heritage network, state ranks aredeveloped by each state and allow a "one-system" comparison of a species or communitiesimperilment state by state. For more information, contact the Pennsylvania Natural HeritageProgram.Global Element RanksG1 = Critically imperiled globally because of extreme rarity (5 or fewer occurrences orvery few remaining individuals or acres) or because of some factor(s) making itespecially vulnerable to extinction.G2 = Imperiled globally because of rarity (6 to 20 occurrences or few remainingindividuals or acres)or because of some factor(s) making it very vulnerable toextinction throughout its range.G3 = Either very rare and local throughout its range or found locally (even abundantlyat some of its locations) in a restricted range or because of other factors makingit vulnerable to extinction throughout its range; in terms of occurrences, in therange of 21 to 100.G4 = Apparently secure globally, though it may be quite rare in parts of its range,especially at the periphery.G5 = Demonstrably secure globally, though it may be quite rare in parts of its range,especially at the periphery.GH = Of historical occurrence throughout its range, i.e., formerly part of theestablished biota, with the expectation that it may be rediscovered (e.g., Bachman'sWarbler).GU = Possibly in peril range-wide but status uncertain; need more information.GX = Believed to be extinct throughout its range (e.g., Passenger Pigeon) with virtuallyno likelihood that it will be rediscovered.G? = Not ranked to date.166