Assessment Notes

Justification

Xylopsora canopeorum appears to be endemic to old-growth coast redwood forests in California where it grows on the trunks of redwood trees. The species has currently only been verified from three localities of which the type locality burned in a high intensity fire in 2020. The extent of known occurrence is 5,893 km² and the area of occurrence is 24 km². The subpopulations are severely fragmented by large-scale timber harvesting reducing old-growth redwood forests to ca. 5% of it’s original range. An ongoing decline in quality and extent of habitat is estimated and ongoing decline in extent and area of occurrence due to large, high-intensity wildfires and climate change. Therefore, it is assessed as Endangered, B2ab(i,i,iii,iv,v).

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Taxonomic notes

This species was described by Bendiksby et al. (2018), and the type specimen was found in Big Basin Redwoods State Park, Santa Cruz County, CA.

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Geographic range

This species occurs in old-growth coast redwood forest in northern California. The species has been found in Jedediah Smith Redwoods State Park, Armstrong Redwoods State National Reserve, and Big Basin Redwoods State Park. It could be present in the other old-growth parks between Jedediah Smith Redwoods SP and Big Basin Redwoods SP, but this has not been verified. This would increase the AOO and the number of localities up to a maximum of around 132 km² and 30 localities.

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Population and Trends

The species has so far only been found on old-growth coast redwood (Sequoia sempervirens) trees. Historical logging led to significant declines in the species' population size and left coast redwood forests severely fragmented, and thus this species' population is severely fragmented. Ongoing losses are now likely due to frequent, high-intensity wildfires throughout the region.

Population Trend: Decreasing

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Habitat and Ecology

The species was observed on coarse, fibrous bark and occasionally on charred bark between 5 and 75 m above ground level along the trunks of large coast redwood trees (Sequoia sempervirens) in old-growth redwood forests. It appears to have an affinity for old and stable bark surfaces on the main trunks.

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Threats

Only ca. 5% of old-growth coast redwood forest are left after decades of timber harvest, so the lichen subpopulations are likely severely fragmented. However, most old coast redwood trees are currently protected in State and National Parks. Wildfires, which are projected to increase in frequency and severity, are the most imminent threat. The southernmost location, Big Basin Redwoods State Park experienced a high intensity fire in 2020, and as conditions get warmer and drier, even parks in the north may experience hot, devastating fires in the future. The occurrences in Big Basin were likely, if not extirpated, then severely impacted by the fire. Extirpation from Big Basin would result in a 97.7% reduction of EOO and a 33% reduction in AOO.

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Conservation Actions

Actions to stop climate change from getting worse are needed. This species is difficult to get accurate knowledge about since it requires climbing of the trees to get to where it grows. The species is too tiny to see from the ground and anatomical and chemical test need to be performed to confidently identify it. Climbing without a research permit is strictly prohibited in all State and National Parks. 

Other possible hosts could be other members of Cupressaceae that share similar bark textural characteristics to coast redwood, and these should be explored.

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Source and Citation

Reese Næsborg, R. 2022. Xylopsora canopeorum. The IUCN Red List of Threatened Species 2022: e.T194662559A213315050. Accessed on 26 November 2025.

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• Country occurrence