USDA Forest Service Celebrating Wildflowers
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What is a Rare Plant?Rare plants may be scarce because the total population of the species may have just a few individuals, or be restricted to a narrow geographic range, or both. Some rare plants occur sparsely over a broad area. Other rare plants have many individuals, but these are crowded into a tiny area; in some cases, a single county or canyon. A third kind of rare plants are those with both few individuals AND a narrow geographic range: these are the very rarest plants. NatureServe, a non-profit conservation organization that provides the scientific information and tools needed to help guide effective conservation action, has developed a consistent method for evaluating relative imperilment of species, with an emphasis on rare species. NatureServe's global conservation status ranks are based on a one to five scale, ranging from critically imperiled (G1/T1) to demonstrably secure (G5/T5). These status assessments are based on the best available information, and consider a variety of factors:
Visit NatureServe's website for more information about their conservation status ranking criteria. Examples
Cushion buckwheat, Eriogonum ovalifolium, is a common and widespread plant of western North America. It has a NatureServe Global Conservation Status Rank of G5. Cushenbury buckwheat, Eriogonum ovalifolium ssp. vineum, on the other hand, is a very rare subspecies only found on special soils in mountains of southern California. It was listed as Endangered in 1994 and is threatened primarily by limestone mining. Cushenbury buckwheat has a NatureServe Global Conservation Status Rank of G5T1, the same G5 for the species Eriogonum ovalifolium, with T1 showing the rarity of the subspecies vineum. |
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Last modified: Friday, 16-May-2008 13:44:58 EDT