The Chapin Mesa milkvetch (Astragalus schmolliae) is a plant species restricted to 18 square kilometers in extreme southwest Colorado in Montezuma County. Among Colorado’s rarest plant species, it is included as a Tier 1 species in the 2015 Colorado State Wildlife Action Plan (SWAP) Rare Plant Addendum, and was proposed but ultimately not listed by the U.S. Fish & Wildlife Service in 2020 as a threatened species under the Endangered Species Act. In order to better understand population status and trends, the National Park Service has funded CNHP to conduct ongoing monitoring of the species since 2001. Monitoring over this period has documented the response of the species to severe drought and the Long Mesa Fire in 2002, which burned almost 40% of the species known distribution.
Results of density and demography data strongly suggest that the positive effects on plant density that were originally seen after the 2002 Long Mesa Fire have reversed. By 2015-2016 the recruitment and reproductive output in the burned area was far below that in the unburned woodland, suggesting that fires may have an overall long-term negative impact. Observations of the vegetation community, soil quality, and moisture and temperature regime paired with Chapin Mesa milkvetch demography data suggest abundant grass cover in the burned area, predominantly cheatgrass, smooth brome and Western wheatgrass, has depressed the milkvetch population. Hypothesized effects in the burned area include:
- Seedlings suppressed due to competition for soil moisture with grasses
- Soil moisture further depleted by higher shallow soil temperature, suppressing pollinators and seedling germination
- Ground nesting bees, an important pollinator, inhibited by lack of bare soil
- Flowers killed by late frosts, which are more common in areas without tree cover
The Parachute penstemon (Penstemon debilis) is a species which is endemic to Garfield County, Colorado, with only four known populations in the world. It is listed by the US Fish & Wildlife Service as a threatened species under the Endangered Species Act and is also listed as a Tier 1 plant species in the 2015 Colorado State Wildlife Action Plan (SWAP) Rare Plant Addendum. Monitoring of population trends is one of the high priority actions listed in the SWAP to meet Parachute penstemon conservation goals. Monitoring enables proactive management by allowing early identification of potential threats or downward trends in population size, and development of strategies to enhance long-term population viability.
With funding from the Colorado Natural Areas Program/Colorado Parks and Wildlife, CNHP has established a long-term monitoring plot for this species on a privately owned state natural area. The habitat occupied by Parachute penstemon is characterized by sparsely vegetated, steep slopes of white and tan shale talus. Because the unstable shale slopes make sampling dangerous and disturb plant habitat, alternative monitoring methods for data collection were developed, using both photo monitoring and taking ocular counts with binoculars within transects marked by telescoping rods. This data establishes a visual record of plant abundance as well as a record of plant and site condition.
Further innovations have continued with a project to monitor and survey for this species using small Unmanned Aerial Systems (sUAS or drones). In 2020, through a partnership with private consultants Aridlands, LLC and EcoloGIS and funding from the National Fish & Wildlife Foundation, 80 flights were flown to develop a safe and effective survey protocol and generate high resolution maps of Parachute penstemon habitat. These data were compared to data collected on the ground by CNHP botanists and the protocol was found to be equally successful for detection. As the project continues, these methods will be used to update population numbers in known occurrences, search for new populations and refine the model of suitable habitat for the species.
To further the conservation of Colorado’s listed species we recommend the following:
- Maintain consistent funding and dedicated resources
- Continue to collaborate and acquire data from agency staff, academic institutions, and private consultants
- Continue field surveys on public, private and tribal lands
- Increase demographic monitoring