by Rosemary Jann
Spring came unusually early to the Southeast and Mid-Atlantic this year, including here in Arlington. Many of us have been delighted to see trees, shrubs, and plants emerging early all over our area because of our unseasonably warm winter.
For scientists who study phenology, these seasonal variations hold a more specific significance.
Phenology studies the timing of recurring life cycle phases in plants and animals and their relationship to weather and climate: when leaf or flower buds break, when insects hatch, when birds start to nest or fruit starts to form. Maintained over multiple years, phenological data can contribute to prediction models that influence decision-making in many fields.
Phenological trends can help determine the best time to plant crops or to treat for insects that damage them. They can predict when flowers are likely to bloom and thus when allergy season is likely to peak, or the best dates for scheduling events like Washington’s Cherry Blossom Festival. Phenological data can help scientists identify the drivers of environmental change and project future trends.
One of the most significant uses for phenological data lies in demonstrating the effects of climate change. “Changes in phenological events like flowering and animal migration are among the most sensitive biological responses to climate change,” according to the USA National Phenology Network (NPN).
Of particular concern is accumulating evidence that rapid climate change is producing mismatches in phenological events that have negative impacts on animals. The chart below, for instance, depicts what happens when caterpillars hatch before migrating birds are ready to feed the nestlings that need those caterpillars to survive.
The NPN was established in 2007 to collect, store, collate, and share phenological data. Since then, it has accumulated more than 30 million individual observation records from over 15 million observers, many of them citizen scientist volunteers who log their data through the NPN’s online tool, Nature’s Notebook. The NPN database currently includes records for more than 1750 species of plants and animals found across the United States.
Volunteer observers for plants follow the NPN’s list of standardized life cycle events or “phenophases” for specific individual specimens, like breaking leaf buds for a tree or open flowers on a perennial. The goal of observation is not necessarily to establish the exact date that buds break but rather through regular weekly monitoring over multiple years to help track trends in the overall timing of onset, duration, and intensity of phenophases in particular species and places.
In 2022, a team of 10 ARMN members began our own multiyear citizen science project to study local phenology at three sites: Arlington Central Library, Marcey Road Park, and Potomac Overlook Regional Park. The project selected plant species from some of Nature’s Notebook’s special regional campaigns in order to maximize the usefulness of our data for scientists and decision makers. Nature’s Notebook’s “Green Wave” campaign targets leaf break and color change in oaks, maples, and poplars to help model the ways climate change is affecting deciduous trees. Also, “Nectar Connectors” studies the availability of nectar for monarch butterflies and other pollinator insects by tracking flower bloom in a selection of common nectar plants like the milkweeds, cardinal flowers, and buttonbushes that the phenology project is monitoring. The beauty of the Eastern redbud tree has made it a ubiquitous landscaping plant across the eastern United States. The new “Redbud Phenology Project” will track flowering and fruiting to determine the effects of latitude, elevation, and climate on redbud phenology.
In addition to contributing to these national campaigns, the ARMN phenology project also hopes to produce information to educate our local constituencies about the effects of climate change. Watch this space for more information about our results later this year.
The National Phenology Network welcomes volunteer observers, and your own front yard or local park could become an observation site. Nature’s Notebook provides all the information you need to get started, including a “how to observe” course. Sign up for an account, register your site, choose your plants or animals, and you’re ready to start monitoring through their mobile phone app or the Nature’s Notebook website. Join the thousands of citizen scientists who are advancing our understanding of climate change through the National Phenology Network!