Article

Invasive Exotic Plant Monitoring at Curecanti National Recreation Area

Cover photo: Oxeye daisies partially along the shoreline of Blue Mesa Reservoir in Curecanti National Recreation Area, with rugged mountains in the background. Image credit: NPS / Amy Washuta
Oxeye daisies (Leucanthemum vulgare), an invasive species, inundated by the 2023 runoff of the Blue Mesa Reservoir in Curecanti National Recreation Area.

NPS / Amy Washuta

What We Wanted to Know

Invasive exotic plants (IEPs) can rapidly colonize new areas, displacing native species and threatening wildlife, natural landscapes, and recreational opportunities. By filling different ecological roles than the plants they replace, IEPs can disrupt ecosystems and create cascading effects. Early detection is essential, as eradicating small populations is far easier and more cost-effective than managing large infestations.

At Curecanti National Recreation Area (CURE), the Northern Colorado Plateau Network (NCPN) wanted to understand which IEPs are most prevalent, where they are spreading, and how their presence changes over time. Identifying these patterns is essential for prioritizing control efforts and allocating limited resources effectively. By mapping IEP distribution and assessing their impacts on native vegetation, we aimed to pinpoint high-risk areas and species that require immediate attention. This knowledge helps park managers make informed decisions to protect native ecosystems.

What We Did

NCPN monitored IEPs at CURE from June 21 to 27, 2023, by surveying riparian areas and trails. This survey initiated the third monitoring rotation, following previous surveys in 2010–2011 and 2014. Crews established transects every 500 meters along monitoring routes, extending perpendicularly from the edge and alternating sides for narrow areas. Quadrats—1 m² sampling frames—were placed at 0.5, 5, and 10 meters along each transect to quantify vegetation cover and soil features (Figure 1).

Figure 1. A map showing invasive exotic plant monitoring routes at Curecanti National Recreation Area, surveyed from June 21 to 27, 2023. The map highlights various routes including Blue Mesa Reservoir 1, Blue Mesa Reservoir 6, Pine Creek Trail, and Dillo
Figure 1. Overview of invasive exotic plant monitoring routes at Curecanti National Recreation Area, including Blue Mesa Reservoir 1, Blue Mesa Reservoir 6, Pine Creek Trail, and Dillon Pinnacles Trail. Surveys conducted June 21–27, 2023. Routes are displayed by type: drainage/lake (blue), trail (purple), and Curecanti NRA boundary (green).

NPS / Aneth Wight

NCPN’s systematic approach focused on priority IEP species. NCPN used detection estimates based on minimum detection target size (MDTS), effective detection distance (EDD), and effective detection swath width (EDSW) (Figure 2).

Figure 2. Diagram illustrating the Effective Detection Distance (EDD) and Effective Detection Swath Width (EDSW) for monitoring at Curecanti NRA.
Figure 2. The maximum Effective Detection Distance (EDD) at Curecanti National Recreation Area ranged from 3–10 meters in 2023, making the Effective Detection Swath Width (EDSW) 6–20 meters.

NPS / Alice Wondrak-Biel, Eliot Rendleman

What We Learned

NCPN staff recorded 1,450 patches of 18 priority IEP species along 55.9 kilometers (34.7 miles) of routes at CURE (Table 1). Canada thistle (Breea arvensis), musk thistle (Carduus nutans), woolly mullein (Verbascum thapsus), and Russian thistle (Salsola spp.) were the most widespread species.

Table 1. Species observed and infestation size class detected along all monitoring routes, Curecanti NRA, June 21-27, 2023.

Species Common Name Total Infestations 1 to Few Plants Few Plants–40 m² 40 - 400 m² 400–1000 m² >1000 m²
Acroptilon repens Russian knapweed 19 0 10 7 2 0
Artemisia absinthium absinth wormwood 1 0 1 0 0 0
Bassia sieversiana summer-cypress 60 1 19 24 14 2
Breea arvensis Canada thistle 409 3 63 284 59 0
Cardaria latifolia broad leaf pepperwort 1 0 0 1 0 0
Cardaria spp. whitetop 25 3 14 8 0 0
Carduus nutans musk thistle 359 30 71 229 29 0
Cirsium vulgare bull thistle 10 7 1 1 1 0
Convolvulus arvensis field bindweed 10 1 3 6 0 0
Leucanthemum vulgare oxeye daisy 32 3 11 14 4 0
Matricaria perforata scentless chamomile 17 4 9 4 0 0
Phalaris arundinacea reed-canarygrass 36 4 9 22 1 0
Potentilla recta sulfur cinquefoil 14 3 9 2 0 0
Rumex crispus curly dock 67 31 24 10 2 0
Salsola sp. Russian thistle 131 1 40 78 10 2
Tamarix sp. tamarisk 1 1 0 0 0 0
Ulmus pumila Siberian elm 3 1 2 0 0 0
Verbascum thapsus woolly mullein 255 29 60 140 26 0
Priority Species - 1,450 122 346 830 148 4


Infestations were higher along reservoir routes, with Blue Mesa Reservoir 1 and Blue Mesa Reservoir 6 showing the higher infestations per kilometer than the trails monitored in this sample year. Canada thistle and musk thistle were the most widespread species. The reservoir routes also had higher percent cover (1.41%) compared to the same routes in 2014 (Figure 3), with increases driven by Canada thistle, musk thistle, Russian thistle, and woolly mullein. Infestation rates declined on the Dillon Pinnacles and Pine Creek trails when compared to the previous sampling periods.

Figure 3. A map showing invasive plant detections along the Blue Mesa Reservoir 1 monitoring route at Curecanti National Recreation Area from June 21 to 27, 2023.
Figure 3. Example map of monitoring routes and quadrats along the southwestern portion of the Soap Creek section of Blue Mesa Reservoir, Curecanti NRA, June 21–27, 2023.

NPS / Aneth Wight

The fluctuating water levels of Blue Mesa Reservoir likely influence species distribution and density, with some patches drowned by rising water during the field season (Figure 4). The 2023 survey highlights ongoing management challenges posed by reservoir conditions and the persistence of priority IEP species.

Figure 4. A flooded area at Blue Mesa Reservoir with musk thistle (Carduus nutans) emerging from the water following the 2023 runoff.
Figure 4. Musk thistle (Carduus nutans) infestations that were inundated by the 2023 runoff.

NPS / Amy Washuta

Park managers can use the findings of this study to enhance detection, management, and prevention of IEP species at Curecanti National Recreation Area.

Information in this article was summarized from Perkins D. W. 2025. Invasive exotic plant monitoring at Curecanti National Recreation Area: 2023 field season. Science Report. NPS/SR—2025/262. National Park Service. Fort Collins, Colorado.

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Curecanti National Recreation Area

Last updated: April 9, 2025