Invasive Plants at Colorado National Monument: The 2021 Survey

Jointed goatgrass. USDA-APHIS.

Why invasive plants matter

Invasive exotic plants (IEPs) are non-native species that cause, or are likely to cause, economic or environmental harm or harm to human health. They spread quickly, displace native plants, and can set off a cascade of effects on wildlife that depended on the natives. Caught early, small populations are cheaper and easier to control — even eradicate.

The Northern Colorado Plateau Network monitors invasive plants in eight National Park Service units: network and park staff list each park's priority species; a field crew searches set routes on a rotating schedule; and plots along the way let ecologists track trends.

Colorado National Monument, 2021

On June 9–15, 2021, the crew surveyed 53.6 km (33.3 mi) of routes and found 395 patches of 15 priority species. Four more species turned up in transects, and eight non-priority species were recorded.

• Four species — yellow salsify, ripgut brome, jointed goatgrass and tamarisk — made up 74% of priority patches.
• Most patches were small (under 40 m2), except ripgut brome and broad-leaf pepperwort.
• Three invasive trees: Russian olive, tamarisk and Siberian elm. ninety-five percent of tree patches were seedlings or saplings, easier to remove than mature trees.
• Cheatgrass was the most common invasive in transects, in more than 63% of transects on every route.

Where: the densest routes were Red Canyon (1.29 patches per 100 m), Monument Canyon (1.25), Hydro 82 (1.06) and Wedding Canyon (1.02). Hydro 88, Limekin Gulch and Kodels Canyon had none. Over the whole record (2005–2021), Red, Wedding and Fruita canyons had the most, with increases driven by jointed goatgrass on all three, yellow salsify in Wedding Canyon and tamarisk in Red Canyon.

Invasive plant patches along the Wedding Canyon route, 2021; jointed goatgrass and ripgut brome were the most frequent. NPS.

Key findings

• Jointed goatgrass is spreading fast: from 8 patches in 2019 to 42 in 2021 (though not all the same routes were surveyed). Even stable routes had a few new patches. It should be targeted for control.
• Four newcomers: Scotch thistle appeared for the first time, in two patches in Monument Canyon; broad-leaf pepperwort, Canada thistle and bull thistle were recorded for the first time since 2012, 2015 and 2015. All are isolated, in 10 patches or fewer — controlling them now could prevent them taking hold.
• Ripgut brome, added to the priority list in 2019, is already among the most common, and may be too widespread to control.
• Japanese chess (Bromus japonicus) was widespread and could be added as a transect species.
• Keep at it: in a few years small patches become large ones, and seedlings become trees that need a chainsaw instead of loppers. Continued eradication gives native species a better chance.

Sources

Based on "Invasive Exotic Plant Monitoring at Colorado National Monument," Northern Colorado Plateau Network, National Park Service, summarizing D. W. Perkins's 2021 report; a work of the United States government in the public domain. Its yellow salsify photograph, credited to Colorado State University through Bugwood.org, is left out.