As National Invasive Species Awareness Week winds down, wildlife and plant experts from the southwestern U.S. are highlighting some of the non‑native species spreading through deserts, plains, mountains and rivers.
All the way from southern Africa’s Kalahari Desert to southern New Mexico, the oryx is one of the biggest and most unusual problems facing White Sands National Park. In an effort to expand large‑game hunting, the New Mexico Department of Game and Fish released nearly 100 oryx onto and near the White Sands Missile Range between 1969 and 1977.
Their population has since grown into the thousands, with human hunters serving as their only significant “predator” in New Mexico. Oryx contribute to overgrazing, which limits food sources for native species. Attempts to keep them out of the park – including construction of a 67‑mile fence – have been largely unsuccessful.
“You may feel lucky spotting these magnificent creatures during your time in the park, but unfortunately, the park isn't nearly as fortunate,” wrote White Sands National Park on Facebook to mark the awareness week.
From clusters of eggs to spotted caterpillars to pesky adult moths, the spongy moth spends its entire lifespan wreaking havoc on trees and shrubs in U.S. forests. Originally from Europe, it has spread across the country, making its way to the San Juan National Forest.
“Its caterpillars defoliate trees and can weaken or kill them over time,” Lorena Williams, spokesperson for the San Juan National Forest, said in a statement to The Journal.
Williams noted it’s important to distinguish between western tent caterpillars – which are native to the ecosystem – and the spongy moth. She said the forest does not monitor for the moths, but people who think they have found one at any stage should report the sighting to Colorado Parks and Wildlife or the Colorado Department of Agriculture for confirmation.
Trouble in the water: Non‑native fish and mussels
According to Williams, many trout species populating Southwest Colorado are not from the region.
“The only trout native to the Colorado River basin on the Western Slope is the Colorado River cutthroat trout,” Williams said, adding that Colorado Parks and Wildlife and the Forest Service are working to repopulate the fish.
Common trout such as rainbow, brown and brook trout come from out of state and were introduced to support angling activities. These non‑native species benefit the state’s outdoor recreation economy.
However, one resident of the Colorado River is not welcome.
“It’s a pretty big deal that there’s invasive mussels on the Colorado River,” said Emily Lockard, director of the Montezuma County Colorado State University Extension.
Colorado Parks and Wildlife calls zebra mussels the “most serious aquatic threat” to the U.S., as they attach to water‑supply structures and crowd out local mussel and fish populations. CPW monitors their numbers as the Colorado River Basin supplies drinking water to millions of Americans.
Garth Nelson, a rangeland management specialist in the Dolores Ranger District, said spotted knapweed, Russian knapweed, milk thistle and leafy spurge are among the non‑native weeds that affect the San Juan National Forest.
All are on the Colorado Department of Agriculture’s “B‑list,” meaning they are invasive plants with the potential to cause significant ecological damage in the areas where they grow. They typically thrive in high‑use areas such as roadways and campsites, according to Nelson.
“We do a lot of manual control, which is just chopping them down,” Nelson said.
Milk thistle is common not only in the forest but throughout Montezuma County.
“Grazing really helps,” Nelson said. “Cows really like to eat the tops of those off before they go to seed.”
He said the San Juan National Forest uses both chemical and manual control methods, including herbicides and hand‑cutting.
It’s not only the San Juan National Forest battling weeds. Russian knapweed remains a problem for the Cortez Parks and Recreation Department.
“Other than just growing prolifically and overwhelming areas, I imagine that it could get to the point where it could start outcompeting natural species,” said Parks and Recreation Director Creighton Wright.
The weed grows in Carpenter Open Space alongside bull thistle, which the department is monitoring.
“It’s got a really pretty purple flower but if it’s not controlled it can really take over an area,” Wright said.
Coinciding with National Invasive Species Awareness Week, the department hopes its next parks superintendent can help mitigate non‑native species.
avanderveen@the‑journal.com
