Sep 20 2019
As habitats get warmer, a plant's life cycle can change. For example, when spring warms up sooner, plants flower earlier. The study of phenology looks at the timing of a plant's life cycle: when a tree "leafs out" in the spring, when a plant flowers, and when it sets fruit. Researchers can use phenology to document rising global temperatures. Herbarium specimens, which are often collected in flower and provide the exact date of when they were collected, are evidence of that species' phenology. Since herbarium specimens have been collected over the last 300 years, we essentially have a history of when plants have flowered and how that has changed as the earth warms up.
Compare different specimens of this local Viburnum acerifolium, which flowers in the spring. Specimens collected more recently flowered earlier than specimens collected over 100 years ago.