In 2007, the Museum’s Botany Department was awarded a grant from the Blasker-Rose-Miah Fund of the San Diego Foundation to conduct local climate-change research using botanical data. The goal was to compile and analyze all available plant-specimen data that has been collected from San Diego County as well as identify locations and key indicator species that exhibit measurable responses to climate.

Our Museum collections tell us about conditions that existed in our history. We have been collecting and preserving plant specimens since 1874 and continue to add new records as a result of the San Diego County Plant Atlas project. The specimen with label data records historic information about San Diego County—what plants grew where, and what time of year they were flowering.

Recent studies have demonstrated that the flowering times of plants can be a useful indicator of local climate change. Historical phenological records are relatively rare; therefore, herbarium specimens are an excellent resource to get a glimpse into the past to see when specific plants were in flower. The SD Herbarium has a large collection of plants collected in San Diego County that can be used in research, particularly in studies on local climate change.

Phenology refers to the timing of specific biological events (for example, first openings of leaf and flower buds, insect hatchings and bird migration) in relation to changes in season and climate. Phenological responses to seasonal changes (such as variation in day-length, temperature, and rain or snowfall) can be ideal indicators of the impact of local climate change.

While no definitive species were identified as having significant shifts in flowering time during the course of this project, a summary of collections data for 85 potential indicator species was compiled. One particular “taxa of interest” (Ceanothus) was selected for detailed analysis, based on criteria developed from a workshop involving local scientists and biologists, and the review of the literature. Phenological data for Ceanothus did not show trends that corroborate with changes in our local climate. Future studies could be done on the targeted taxa to see if some plants are responding to changes in our climate.