Nebraskaland

12 Nebraskaland • July 2020 IN THE FIELD The Colorado butterfly plant is a High Plains rarity restricted to a few counties in southeastern Wyoming, northcentral Colorado and far western Kimball County, Nebraska. Although it has seen drastic declines in Nebraska in recent decades, in other parts of its range, conservation of the plant has been a model of success. A biennial to short-lived perennial, the Colorado butterfly plant (Oenothera coloradensis) produces only a leaf rosette its first year. The following years, it sends up flowering stems reaching 2 feet tall. The flowers have four pinkish petals and long stamens and style. In Nebraska, the plant blooms in August, and characteristic of the evening primrose family to which it belongs, the individual flowers open from late afternoon until dawn. The butterfly plant is mainly pollinated by night- flying moths. The finicky plant inhabits wet meadows and other floodplain grasslands where a high water table keeps soils constantly moist, but only at elevations of 5,000 to 6,400 feet. Furthermore, the butterfly plant grows only in relatively open habitats created by disturbances, such as fire, grazing and flooding. If the surrounding vegetation becomes too dense, increasing competition for sunlight and other resources, the plant falters. In 1985, the butterfly plant was first discovered in Nebraska when botanists also doing surveys in adjacent Wyoming found about 2,000 plants growing in sandy and gravelly soils in the Lodgepole Creek floodplain. Surveys in the early 2000s found the plant in decline, and a 2008 survey documented only 12 plants. Several of the plant's habitats had been overtaken by the non-native and highly aggressive Canada thistle. The moisture-loving plant's collapse, however, was due mainly to a drastic decline in flows in Lodgepole Creek caused by center-pivot irrigation development, and the associated decline in its floodplain groundwater levels. During the last few decades, the creek has been, literally, pumped dry. Fortunately, the Colorado butterfly plant's fate in Colorado and Wyoming is far more encouraging, making it one of the many successes of the federal Endangered Species Act. There, shortly after the plant's listing in 2000 as a threatened species, the U.S. Fish and Wildlife Service and its conservation partners began efforts to conserve its habitat. The city of Fort Collins, Warren Air Force Base and 11 ranchers whose property contained the butterfly plant signed voluntary agreements to: limit herbicide use near plants, time haying to not damage its flowers and seed pods, use prescribed fire and managed grazing to maintain early successional habitat, and maintain stream flows and groundwater levels. These efforts were so successful that in 2019, the Colorado butterfly plant was removed from the federal list of threatened species. During surveys along Lodgepole Creek in 2018, seven butterfly plants were found in a small area where overflow from cattle tanks had saturated the floodplain soil. This gives hope that a seedbank still persists along the creek, and if its flows could be somehow restored, the plant may yet survive in Nebraska. But for now, it remains a state threatened species. By Gerry Steinauer THREATENED AND ENDANGERED: THE COLORADO BUTTERFLY PLANT BONNIE HEIDEL, WYOMING NATURAL DIVERSITY DATABASE

• Cover