Chapter 20 

 Endangered, Threatened 



and Rare Plants 



Authors: Norman Famous, Craig Ferris 



Endangered species are those considered in danger of extinction throughout all 

 or a significant portion of their range. Threatened species are those likely 

 to become endangered within the forseeable future throughout significant 

 portions of their ranges and rare plants are those having small or restricted 

 populations in particular areas of their ranges, but are not endangered. 



A variety of the estuary monkey flower (Mimulus ringens var. colpophilus) , 

 found in some estuaries in coastal Maine and Canada, was recently considered 

 endangered by the U.S. Fish and Wildlife Service (FWS) . Six other plants 

 found in coastal Maine were listed as threatened by the Smithsonian Institute 

 (table 20-1; Ayensu and DeFilipps 1978). These species are no longer listed 

 as endangered or threated because critical habitats in which they are found 

 were not identified (see "Protection of Endangered, Threatened, and Rare Plant 

 Species" below). Another 84 plant species are considered rare in Maine by 

 either the Maine State Planning Office, the New England Botanical Club, or 

 plant taxonomists familiar with the species (table 20-2). 



Plants are usually considered endangered if they have very limited 

 distributions, or if they are found in restricted or fragile habitats. Plants 

 also may be endangered because of destruction, alteration, or curtailment of 

 their habitat, or because of exploitation, disease, or unknown causes. Rare 

 plants may be rare throughout their ranges, or they may be rare only on the 

 fringes of their ranges. Most species considered rare in Maine are on the 

 periphery of their normal ranges and may be relatively common elsewhere. 



Endangered, threatened, and rare plants may occur in relatively 

 undifferentiated habitats, such as mature deciduous forests and mature spruce- 

 fir forests, or they may be found in locally unique, unusual, or isolated 

 habitats (Ayensu and DeFilipps 1978). The latter habitats may be ecologically 

 or geographically restricted, fragile, or otherwise specialized due to various 

 combinations of climatological, geological, hydrological , and biological 

 factors. Unique or specialized habitats in coastal Maine that support rare 

 plants include plateau bogs, forested wetlands dominated by Atlantic white 

 cedar or northern white cedar, coastal headlands and islands, palustrine and 

 riverine wetlands, and estuaries. 



20-1 



10-80 



