BLM botanist contributes years of data on tiny plant

The only place in the world to find the skiff milkvetch is in southwest Colorado, on about 310 acres of mostly public lands managed by the BLM in Gunnison and Saguache counties.

A member of the legume family, the skiff milkvetch (Astragalus microcymbus) is a tiny plant that grows in gravelly soils in sagebrush country. The plant reaches a maximum height of a foot and produces small white flowers with hints of purple. 

close-up of skiff milkvetch plant
Close-up of skiff milkvetch plant

For 24 years, BLM Colorado botanist Carol Dawson has been watching over this tiny plant.

In 1995, Dawson was working for the Denver Botanic Gardens, when she and a crew of four from the BLM and The Nature Conservancy, first started a demographic monitoring program for the species. 

Every year, usually in July, Dawson and crew would head west to the skiff milkvetch's habitat. The first step in demographic monitoring is looking for trends - if plant numbers are increasing or decreasing over time, how long the plant lives, if it flowers, and if it produces seeds. Soil moisture, temperature, and climate are monitored every year. The crew also monitors and records physical data about the plants including new growth, dead plants, other plants in the plots, if the plant flowered, if it was eaten by animals, and other observations. 

skiff milkvetch plant
Skiff milkvetch plant

Monitoring isn't an easy task. It occurs over a minimum of 10 years but can last longer. The more data, the better. In the fall of 2001, Dawson came to work for the BLM as a botanist and continued monitoring the plant with staff from the Denver Botanic Gardens and the BLM.

The data Dawson and others collected over the last 24 years went towards a purpose – to provide the U.S. Fish and Wildlife Service with the best data available so the agency can decide whether the species needs protection under the Endangered Species Act. In 2010, the USFWS determined the skiff milkvetch warranted Endangered Species Act protection, but that listing the species was precluded at the time by other listing actions of higher priority. 

monitoring for the skiff milk vetch in southwest CO
Monitoring for the skiff milkvetch in southwest Colorado

Dawson has been in it for the long haul, which is why, last December was special. 

In December 2019, the USFWS announced the skiff milkvetch is maintaining a stable, long-term population and is not warranted for listing under the ESA. The USFWS used data gathered by the BLM, Colorado Natural Heritage Program, Colorado Natural Areas Program, and Gunnison County to develop a Species Status Assessment, which contains the best available science and helped inform this decision.

"I'm happy to be a part of this decision," said Dawson. "Our goal is to help get the best information and data to the USFWS so good decisions can be made."

Dawson's work isn't complete. She's already eager to work on other plant species. With Dawson at the helm, the BLM is working with the USFWS to gather data for several other plant species in 2020.

To learn more about the skiff milkvetch, visit:

Skiff milkvetch habitat
Skiff milkvetch habitat

The purpose of the Endangered Species Act is to protect and recover imperiled species and the ecosystems upon which they depend. A rigorous scientific analysis evaluating potential threats as well as current and future conditions is conducted prior to making any determination to list or not list a species.