Nature’s clock and climate change

Author: Jessica Hellmann

March in the Midwest and East US was very warm, usually so. Chicago experienced 8 days over 80 degrees, when there is usually only one day over 80 degrees in April. Unofficial reports suggested that spring flowers and leaf flush come to Chicago 5-6 weeks ahead of normal. April turned cooler but peonies in Indiana and Michigan are still blooming two weeks before Memorial Day. The peony is a patron flower of Memorial Day here in the Midwest. As the climate changes further, we might need to find a new flower for honoring the graves of loved ones on Memorial Day.  


So who is keeping track and making sense of this stuff—these anomalies in climate and the timing of creatures? The answer is the National Phenology Network (NPN), a government-funded organization that is collating and investigating one of the most visible aspects of climate and climate change. “Phenology” means “ecological timing” in the parlance of ecologists. The NPN sits in Tucson, AZ but interfaces with scientists, managers, and the public nationwide. Anyone can submit observations to the NPN to help in their research. You could post an observation about the first arrival of a migratory bird in your neighborhood or the timing of lilac flowering in your yard. Postings are made via their public database at Nature’s Notebook. You can also visualize data that others have contributed to the database at


Several studies have shown that climate change is altering the timing of life (see this paper or this one). Spring has come earlier to many parts of the country and world, leading in some cases to mismatches of species (e.g., see this study). Experiments also show that warming can change the timing of two or more interacting species, changing them in ways that affects their overlap and individual success. Take the endangered species, the Bay checkerspot butterfly, for example. When we warmed the Bay checkerspot and its habitat, we found that warmer conditions accelerate the insect and it’s food plants. But that acceleration happened faster in one host plant species than another, increasing the butterfly’s reliance on the second host species, when and where it is available. This result means that warming affects the butterfly itself but also affects its success by changing the timing of its food.


Recording observations about the timing of life is one of the easiest ways to track the effects of climate change. Such observations are a kind of “biometer” (like “thermometer” but measures how creatures perceive the climate). There are several things that researchers need to learn about phenology to maximize the value of its measurement, however. First, we need to learn if shifts that we see in species’ timing are useful changes that represent adaptive (good) adjustments that species are making, or if those changes are maladaptive adjustments that undermine a species’ or ecosystem’s success. We also need to better understand *why* species are changing at all: What cues are they reacting to? What genes or traits control these responses? And why do some species or populations adjust and others do not? Finally, we need to determine how much of the changes in species and ecosystem timing are due to exposure and how much is due to sensitivity. In other words, are species and populations changing because the climate where they live is shifting rapidly, or are they instead finely tuned to climatic variables?


We can look in the future to the NPN for answers to these and other questions. Please help the NPN by contributing your own observations. (Anybody can do this!) And keep an eye on the NPN as they grow and discover new things about our changing world.


Also, check out efforts related to the NPN at the Chicago Botanic Garden, called Project Budburst.