Coefficients of Conservatism


This workgroup was funded by an EPA Region 4 Wetland Program Development Grant issued to the North Carolina Department of Environment and Natural Resources. One of the objectives on this grant was to gather expert botanists from across the Southeast Region for the purposes of developing a database of wetland plant quality ratings, called Coefficients of Conservatism. Coefficient of Conservatism values (C values) are used in the calculation of Floristic Quality Index as indicators of habitat quality. Average C value of a study site is also a useful indicator.
This rating system was originated by Gerould Wilhelm in the 1970s in response to NEPA regulations as a way of measuring the degree to which impact to an area is irreversible or irretrievable.Guidance for the application of this rating system was published in 1997 by Taft et al., and it is becoming widely adopted across the country as a means of facilitating site quality assessments. These Coefficients vary from 0-10, and indicate the degree to which a species is found growing in unique environmental conditions. Plants are given a low rating if they are able to tolerate a very wide range of conditions and are found in a variety of habitats/locations. A high rating is given to species which have very specific requirements and cannot exist outside of those conditions. Non-native species are generally given a rating of zero.
The goal of this project was to generate an extensive wetland plant database for the 8 state region of the Southeast: Kentucky, Tennessee, North Carolina, South Carolina, Georgia, Alabama, Mississippi, and Florida. This database of C values is useful to wetland managers, mitigation providers, governmental agencies, natural heritage programs, consultants, academics and the like.


Southeast Wetland Plant C Value Database, Version 2 (.zip) - updated March 26, 2014

Note: In Version 2, two species (Aesculus glabra and Agalinis heterophylla) previously noted as Upland species in Version 1 have been changed to Non-upland in Version 2 with an added note that they can sometimes be found in wetlands. C values for these species were present in Version 1 and have not been changed in any way.


Ecoregions Map with Descriptions

Ecoregions Map with Counties


Methodology for Southeast Wetland Plant C Value Database - updated October 14, 2013

Final Report  (March 2014)


March 19, 2013 - Kick-off Webinar:

October 4, 2013 - Webinar to the SEWWG


Article by Taft et al. (Floristic Quality Assessment for Vegetation in Illinois) 


 C of C

Questions can be directed to Kristie Gianopulos at 919-743-8479 or email to

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