Herbarium specimens offer a unique opportunity to measure changes in plant phenology over broad time periods and geographic ranges. Many of the specimens currently housed in herbaria were collected in the 19th and 20th centuries, but in just the last decade there has been a huge increase in herbarium-based phenology research-- particularly addressing modern questions about how plants are responding to climate change.
Earlier this year, Richard Primack and I were co-authors on a review paper led by Charlie Willis entitled "Old Plants, New Tricks: Phenological Research Using Herbarium Specimens." The review, published in Trends in Ecology & Evolution, provides a thorough assessment of how herbarium specimens have already been used in phenology research, with most studies focusing on flowering, in northern, temperate biomes.
We also discuss the future of herbarium specimens, with a special focus on the widespread digitization efforts currently underway. Digitized specimens are already being used by researchers to access more specimens in more locations than they could visit in person, and to use citizen science efforts to identify phenological stages online. Lastly, we review the biases inherent in using herbarium specimens, from those that arise during collection, to digitization, to observation.
For our part, we plan to continue using herbarium specimens--including digitized specimens--to improve our understanding of species-specific effects of climate change, in both spring and autumn!