Wright's marsh thistle Cirsium wrightii
ESA status: candidate for listing

Wright's marsh thistle pc Robert Sivinski

Much to the frustration of conservationists and land managers, thousands of non-native plants are thriving and proliferating in the American West, while many native species are struggling to survive. Such is the case for thistles. For example, non-native Canada thistle and bull thistle (from Eurasia and North Africa) and Italian thistle (from the Mediterranean region), are flourishing, while native thistles in the West, such as Wright’s marsh thistle, have become imperiled.

Wright’s marsh thistle is an impressive species to behold. The plant, related to the sunflower, can grow to 8 feet tall. It produces a single, central stalk with dark green succulent (and mildly prickly) leaves and numerous slender flowering branches that extend from the upper third of the main stem. The thistle produces white or pink flowers from August to October. As its name implies, Wright’s marsh thistle grows in wetlands, typically in alkaline soils near seeps, springs, and along marshy edges of streams and ponds.

The last remaining populations of Wright’s marsh thistle occur in New Mexico. The plant appears to be extirpated in Arizona; populations previously reported in Texas were, in fact, misidentified; and the species’ status is unknown in Mexico. Four known populations of the thistle have been lost in New Mexico, and alteration of the plant’s rare wetland habitat has likely contributed to extirpation from additional sites. The thistle now occurs at just eight locations in the state and some populations number just a few dozen plants. The largest population (numbering a few thousand thistles) is found on Bitter Lake National Wildlife Refuge. A new population estimated at a few hundred to a few thousand plants was recently found at Blue Spring.

More than half of all wetlands in the contiguous United States have been drained, filled, dewatered and converted to other uses. Wetlands in New Mexico have suffered from centuries of mismanagement. An estimated 36 percent of wetlands were lost in New Mexico between the 1780s to the 1980s, and wetlands are extremely rare in the state. Diversions and groundwater pumping for agricultural and urban use, invasive species, drought, and climate change continue to degrade and eliminate wetland habitat in New Mexico, including all sites where Wright’s marsh thistle occurs.

Citing these threats, the species’ small population, and a lack of protective regulations, WildEarth Guardians petitioned to list Wright’s marsh thistle under the Endangered Species Act in 2008. The U.S. Fish and Wildlife Service concurred with Guardians that the species is imperiled and designated the plant as a candidate for listing in 2010.

photo credit: Robert Sivinksi, New Mexico State Forestry Division