Cryptic paw (Nephroma occultum) COSEWIC assessment and status report: chapter 8

Limiting Factors and Threats

Nephroma occultumis limited by poor dispersal capabilities and the availability of suitable habitat, namely humid old growth cedar-hemlock forests. These forests have diminished in abundance in step with the progressive expansion of forest harvesting. Forest harvesting has resulted in two documented extirpations, and is very likely responsible for many more; it is a serious threat to this species. Additional threats from hemlock looper infestations and fire are predicted to increase in severity and frequency as mean annual temperatures rise, a reflection of global warming. Global warming may also lead to an increase in the prevalence of summer drought conditions, which is an important habitat limitation. Cumulative effects of harvesting, climate change, insect infestations and fire are expected to have a negative influence on remaining N. occultum habitat.

The development of a provincial Old Growth Management Policy, which provides targets for managing designated Old Growth Management Areas (OMGAs) at the landscape level, may aid in the conservation of rare lichens on unprotected provincial lands (British Columbia Ministry of Forests 1995). One important limitation of this policy is that OGMAs are often “recruited” from forests which have been previously harvested. Harvested OGMAs are ineffective refuges for dispersal-limited lichens such as Nephroma occultum. While the Old Growth Management Policy may recognize the importance of old growth forests, in failing to differentiate between original old growth forests and recruited old growth forests, the efficacy for conservation will be compromised, at least for lichens.

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