Lomatium refugianum

Lomatium refugianum is a perennial forb occurring on barren ridgelines on felsic to mafic volcanic substrates in alpine to sub-alpine habitats of the east-central Cascade Mountains region of Yakima County, Washington in the western United States. There are an estimated four occurrences of this species, all of which occur within the W.O. Douglas Wilderness of the Okanogan-Wenatchee National Forest. Just one population (the type locality) has a large population size and good estimated viability, with additional occurrences containing fewer than a couple hundred plants each. Direct threats to this species appear to be minimal, but climate change shifting habitat conditions and conifer encroachment into open ridgeline habitat is a serious concern for this high elevation plant.

Lomatium refugianum is endemic to western North America, where it is found in the east-central Cascade Mountains region of Yakima County, Washington in the United States (Darrach et al. 2024). Range extent was estimated to be approximately 75 square kilometers by Darrach et al. (2024).

By applying a 1 km separation distance to the known population sites mapped in Figure 10 of Darrach et al. (2024), it is estimated that there are four occurrences rangewide. Separation distances between the four localities range from three to 20 kilometers.

Direct anthropogenic threats to Lomatium refugianum appear to be low, as plants occur in wilderness alpine and sub-alpine regions of the Cascade Mountains, and habitat disturbance was not observed, at least at the type locality (Darrach et al. 2024). There also were no impacts from invasive species observed. However, climate change and associated habitat loss is a serious concern, because this species occurs on high elevation peaks and there are limited elevational gains for shifting habitat (J. Miller, pers. comm., 2024). Conifer encroachment is also a threat to Lomatium refugianum, which requires open habitat (M. Darrach, pers. comm., 2024). Climate change can influence conifer encroachment by extending growing seasons, altering the timing and abundance of precipitation, and causing changes to snowpack, which can create conditions that favor conifer establishment; though microclimate, aspect, and tree species are also important factors governing patterns of conifer encroachment (Hagedorn and Flower 2021).