Climate Change Vulnerability Assessment of Rare Plants in California

We assessed climate change vulnerability of 156 rare plant species of California. Our work can
be divided into three complementary parts. First (1), we assigned a climate change vulnerability score to each of 156 rare plant species. The vulnerability scores are based on life history attributes and distribution model results, as specified by the Climate Change Vulnerability Index (CCVI) of NatureServe. The resulting CCVI scores were extremely vulnerable (n = 2), highly vulnerable (n = 40), moderately vulnerable (n = 57), presumed stable (n = 32), increase likely (n = 16), and insuficient evidence (n = 9). The most vulnerable species in our subset were Piperia yadonii, Mimulus purpureus, Calliandra eriophylla, Limosella subulata, and Taraxacum californicum.

Second (2), we conducted a sensitivity analysis which showed that the change in suitability predicted by distribution models for future climates were highly dependent upon both model algorithm and model configuration. However, for 60 of the 156 species, climatic suitability was predicted to decline regardless of model algorithm and model configuration. Third (3), we calculated the topographic variability around known occurrences of each species (‘topographic complexity’). The topographic complexity value of each species can be used to rank a group of species at a finer scale. For example, of the 40 species in the highly vulnerable CCVI score, some occur in relatively f!at landscapes (low topographic diversity) and others occur in topographically dissected landscapes (high topographic diversity). It is possible that species that occur in topographically complex landscape will be less vulnerable to climate change because they can find local refugia.

We make recommendations for improving NatureServe’s CCVI in general, and make specific recommendations for plants. Our results can be used to guide monitoring, management, and conservation plans for rare plant species.