Skiff Milk-Vetch and
Photo by Alicia Langton
December 2010: The U.S. Fish and Wildlife Service has determined that skiff milkvetch (Astragalus microcymbus) and Schmoll’s milkvetch (Astragalus schmolliae) warrant protection under the Endangered Species Act, but that listing the species under the Act is precluded by the need to take other listing actions of a higher priority.
We will add skiff milkvetch and Schmoll’s milkvetch to its list of candidate species and review their status annually. If we propose to list skiff milkvetch or Schmoll’s milkvetch in the future, the public will have an opportunity to comment.
Both of these species have restricted ranges. Skiff milkvetch is known largely from a 20‑square mile area just southwest of Gunnison, Colorado, and Schmoll’s milkvetch is known from about 4,000 acres in Mesa Verde National Park and the Ute Mountain Ute Tribal Park. Both species are herbaceous forbs in the pea family that live for several years, retreating underground during the winter months. Otherwise, the two species are quite different. They are separated by over 100 miles, are not closely related within the Astragalus genus, and have very different habitat requirements. Skiff milkvetch is found on sparsely vegetated slopes within open sagebrush habitat, and Schmoll’s milkvetch is found within pinyon-juniper forests on mesa tops.
The primary threats to skiff milkvetch are habitat fragmentation and degradation, increasing recreational use (primarily from roads and trails within the Hartman Rocks Recreation Area), and the inadequacy of existing regulatory mechanisms on private and Federal lands. Survey and monitoring data suggests the species is in decline.
The primary threats to Schmoll’s milkvetch are modification of its habitat due to the invasion of non-native cheatgrass following wildfires, prescribed fires, and fire break clearings. Cheatgrass is highly flammable and increases fire frequency. Frequent fires are likely to prevent recovery of the species’ pinyon-juniper habitat. There are no landscape-scale methods known to be effective in controlling cheatgrass. Drought due to the warmer and drier climate trend in the Southwestern United States is a significant contributor to degradation of the habitat for this species.
- Federal Register Notice: December 15, 2010 12-Month Finding on a Petition To List Astragalus microcymbus and Astragalus schmolliae as Endangered or Threatened
- Press Release: December 15, 2010 Listing of Skiff Milkvetch and Schmoll's Milkvetch Under ESA Found Warranted But Precluded