The status of rare and vulnerable species in Massachusetts is dynamic and may change due to many factors such as: our knowledge about their status in the state; changes in biological populations; and our understanding of their habitat requirements.  Thus, the status of species on the Massachusetts List of Endangered (E), Threatened (T) and Special Concern Species (SC) is reviewed periodically and some changes may therefore be recommended.   Listing species in Massachusetts is based on three primary factors: species rarity, population trends, and threats to the species in Massachusetts.  Details about the listing criteria process can be found in Listing Endangered Species in Massachusetts: The Basis, Criteria and Procedure for Listing Endangered, Threatened and Special Concern Species pdf format of Listing Endangered Species in Massachusetts
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Recent Changes to the Massachusetts List of Endangered (E), Threatened (T) & Special Concern (SC) Species