Vegetation Classification and Mapping Project Report - USGS

USGS-NPS Vegetation Mapping Program
Colonial National Historical Park
Appendix E. Definitions of global and subnational (state) conservation ranks.
NatureServe and the Network of Natural Heritage Programs and Conservation Data Centers
work together to assign conservation status ranks to elements of biodiversity (plants, animals,
and ecological communities). These ranks have been developed using range-wide data collected
by the Natural Heritage Network for nearly three decades and are critical in setting conservation
priorities. Community types are ranked on a global (G), national (N), and subnational (S) scale
of 1 to 5, with 1 indicating critical imperilment due to rarity, endemism, and/or threats, and 5
indicating little or no risk of extirpation or elimination.
The primary ranking factors used in assessing the appropriate conservation status rank for an
ecological community element are: (1) the total number of occurrences, and (2) the total area
(acreage) of the element. Secondary ranking factors, such as the geographic range over which
the element occurs, the threats to the occurrences, and the viability of the occurrences, also affect
the rank.
Additional factors that have been used in arriving at an assessment of a community’s range-wide
(global) rank include the geographic range over which the type occurs, the long term decline of
the type across this range, the degree of site specificity exhibited by the type, and the rarity
across the range based on state ranks assigned by state Natural Heritage Programs.
To learn more about Natural Heritage Methodology, go to
http://www.natureserve.org/prodServices/heritagemethodology.jsp.
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