Skiff milkvetch Astragalus microcymbus
ESA status: candidate for listing
The skiff milkvetch is a perennial wildflower that occurs in sagebrush and sagebrush-juniper communities in Gunnison and Saguache counties in Colorado. It grows to a foot tall and produces clusters of small white flowers tinged with purple from mid-May through July. The “microcymbus” portion of its name means “small boat,” hence the common name, “skiff,” referring to its boat-shaped fruits. The plant has experienced precipitous population declines and faces imminent threats.
The Denver Botanic Garden monitored skiff milkvetch populations for 15 years (1995-2009) and predicted that all populations of the species will fall below 20 individuals and become effectively extinct by 2030. Particularly sharp declines from 1995-2002 may have been caused by drought, to which the skiff milkvetch is susceptible. Climate change will likely worsen droughts and other perils to the plant. The species is also threatened by cheatgrass and other non-native plants; development; grazing by domestic livestock and native species; and a lack of legal protections.
The skiff milkvetch has waited more than 35 years for federal protection despite having been petitioned three times for listing under the Endangered Species Act (ESA). The Smithsonian Institute was the first to petition to list the flower in 1975. The U.S. Fish and Wildlife Service responded by proposing it for listing in 1976, but then withdrew that proposal in 1979, at which time the plant was instated to the candidate list. The Biodiversity Legal Foundation and an individual petitioned to list the species again in 1993. The agency ignored that petition, and then dropped skiff milkvetch along with more than 2,000 other species from the candidate species list in 1996. WildEarth Guardians filed a third petition to list skiff milkvetch under the ESA in 2007, and the Service responded by placing the species back on the candidate list.
Skiff milkvetch current range has been reduced to just 83 acres. Development near Gunnison, Colorado, cheatgrass incursion, and global warming threaten to eliminate the species from this small patch of habitat. The skiff milkvetch can be saved, but not without the protections of the ESA. It is up to the Fish and Wildlife Service to finally list the species.
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photo credit: Tom A. Grant III