This species is not currently threatened by may warrant listing in the future. It’s AOO < 500km2 (AOO = 180 km2), which would potentially qualify it for listing under the B criterion. It does not meet the specifications of the severely fragmented designation, as >

50% of the known sites where it occurs are not small and isolated. However, this could change in the future as ~35% of sites are severely fragmented. There is a past and ongoing decline of habitat availability and quality throughout the distribution of the species, especially in areas where it is currently most abundant.

Originally described by Runemark (1956), Rhizocarpon cookeanum is a very distinctive species and easily distinguished from other yellow species in the genus by its muriform spores, each ascus containing two spores, and a K+ purple epihymenium.

Rhizocarpon cookeanum is endemic to western North America. It occurs in eastern Washington east to western Montana and south to Nevada and east-central California. It is most abundant in southeastern Washington.

The population trends are currently unknown and require further research.

Rhizocarpon geographicum is most frequently found on basalt and granite in ponderosa pine savannas with open canopies. It grows in arid or semi-arid climates with hot summers and cold winters where most precipitation falls during the winter as snow.

The areas where Rhizocarpon cookeanum is most abundant have historically been subjected to large-scale land use transitions from sagebrush-steppe, pine savannas, and grasslands to agriculture (Sampson et al. 1994, Hessburg and Agee 2003). In the past two decades, rapid development has begun putting additional pressure on remaining natural areas. Installation of numerous wind farms in the region may pose an additional threat to the species (Copeland et al. 2011). As this species is rock-dwelling, the increased popularity of rock climbing in the region, and development of new climbing areas is also likely a threat (Holzschuh 2016). Cattle grazing is another likely threat to this species.

Rhizocarpon cookeanum is recognized as a species that needed monitoring in the state of Washington, and was given official ranking as being rare in the state (Northwest Lichenologists, 2011).

To better conserve this species, large-scale surveys throughout its range must be conducted to more accurately assess its abundance in different portions of its range, and to assess threats at sites of greatest conservation value (i.e., where it is most abundant).

Research on the degree of threat posed by expansion of housing developments, wind farms, and rock climbing are most needed. A thorough search throughout the region for additional subpopulations, especially any large subpopulations, is essential for prioritizing preservation of key sites. Finally, quantitative studies of the number of individuals within a subpopulation are required to establish long-term monitoring programs for the species.

None

Copeland, H.E., Pocewicz, A. and Kiesecker, J.M., 2011. Geography of energy development in western North America: potential impacts on terrestrial ecosystems. In Energy development and wildlife conservation in Western North America (pp. 7-22). Island Press, Washington, DC.

Hessburg, P.F. and Agee, J.K., 2003. An environmental narrative of inland northwest United States forests, 1800–2000. Forest Ecology and Management, 178(1-2), pp.23-59.

Holzschuh, A., 2016. Does rock climbing threaten cliff biodiversity?-A critical review. Biological conservation, 204, pp.153-162.

Runemark, H., 1956. Studies in Rhizocarpon. I. Taxonomy of the yellow species in Europe. Opera Botanica, 2(1), p.152.

Sampson, R.N., Adams, D.L., Hamilton, S.S., Mealey, S.P., Steele, R. and Van De Graaff, D., 1994. Assessing forest ecosystem health in the Inland West. Journal of Sustainable Forestry, 2(1-2), pp.3-10.