Relevance

Long-petaled lewisia (Lewisia longipetala) is a low-growing perennial plant in the Purslane (Portulaceae) family. The species has pale pink flowers and fleshy leaves and grows at high elevations (7,874 to 12,500 feet) in moist, rocky habitats directly below persistent snowfields (Halford 1992, Halford and Nowak 1996, McKnight and Rowe 2015). It grows in association with snowbank vegetation communities and optimum habitat is north-facing low gradient gravelly or bouldery slopes with low vegetation cover (Halford and Nowak 1996). The worldwide distribution of long-petaled lewisia is limited to 16 element occurrences in the northern Sierra Nevada crest in El Dorado, Nevada, and Placer Counties, California (McKnight and Rowe 2015, CNPS Rare Plant Program 2016). The species is currently designated as a USDA Forest Service sensitive species and a TRPA sensitive plant species. It has a California State Rank of S3 (vulnerable), a Global Rank of G3 (vulnerable), and is included in the California Native Plant Society Inventory of Rare and Endangered Plants on list 1B.3 (rare, threatened, or endangered in California; not very threatened in California) and is therefore eligible for state listing (CNPS Rare Plant Program 2016). The long-petaled lewisia populations in the Tahoe Region are among the largest (CNPS, 2016), and are crucial for maintaining the viability of the species (Engelhardt and Gross 2011b). As a snowbank obligate species (Halford and Nowak 1996), long-petaled lewisia is especially threatened by reduced snowpack in a warming climate. The health of this species is an indicator of climate change impacts on snowbank communities in the Lake Tahoe Region and northern Sierra Nevada.

Human and Environmental Drivers

As a result of climate change there is likely to be a decrease in snowpack and persistence and an increase in rain versus snow predicted for the northern Sierra Nevada (e.g. Mastrandrea and Luers 2012, Safford et al. 2012). This shift poses the most significant threat to this snowfield dependent species. Populations occurring at further distances from persistent snowfields, or on drier south-facing aspects or steeper slopes have lower densities and individual plants are smaller (Halford and Nowak 1996). Dry conditions with few persistent snowfields may have already contributed to observed declines in two populations (McKnight and Engelhardt 2013). Climate change could also lead to competitive exclusion if other plant species are able to expand into areas that previously supported long-petaled lewisia (Halford and Nowak, 1996). Most populations of long-petaled lewisia occur in remote, off-trail areas in designated wilderness; thus direct impacts from human activities are relatively low (Halford and Nowak 1996, McKnight and Rowe 2015). Human activities that pose direct threats include recreational activities that might trample or uproot plants (e.g., camping, hiking, equestrian use, trail construction, snowmobiles) (Halford 1992), horticultural collecting (CNPS Rare Plant Program 2016), and road construction that might alter hydrology and degrade habitat (McKnight and Rowe 2015).

No related projects or programs defined for this indicator.