USA National Phenology Network hits 30 million observations

Monday, August 15, 2022

This month, the USA National Phenology Network, which is housed in the University of Arizona College of Agriculture, Life and Environmental Sciences’ School of Natural Resources and the Environment, hit a milestone: 30 million observations. Through their phenological programs – including the citizen science online app Nature’s Notebook – the USA NPN brings together volunteer observers, government agencies, non-profit groups, educators and students of all ages to monitor the impacts of climate change on plants and animals in the United States.

You may be asking, what is phenology? Think of it as nature's calendar - when saguaros blossom, when monarch butterflies migrate south, or when cicadas first appear.

The Intergovernmental Panel on Climate Change released a report in 2007 that stated “Phenology – the timing of seasonal activities of animals and plants – is perhaps the simplest process in which to track changes in the ecology of species in response to climate change.”

Since that time, the USA-NPN has engaged tens of thousands of participants representing all walks of life in documenting phenological events in their backyards. These data have been crucial to understanding changes in the timing of seasonal events in plants and animals in response to changing climate conditions and other pressures.

The USA-NPN has been shaped by input from hundreds of scientists and natural resource managers to become the country’s premier organization for phenology data collection, storage, and sharing.

“Reaching 30M records speaks to the depth of USA-NPN’s engagement as well as the incredible commitment among tens of thousands of professional and volunteer observers and partners across the country,” said Theresa Crimmins, research professor in the School of Natural Resources and the Environment and Director of the USA National Phenology Network.

“This milestone gives us a chance to reflect on the current strengths of the dataset and also what changes we might consider going forward For example, how can the USA-NPN best support pressing science and climate change questions and societal needs?” Crimmins said.  “We are excited about emerging opportunities for the phenology data the USA-NPN curates, such as predicting the timing and severity of allergy season and providing guidance on plant selection for those working on pollinator restoration. There is so much potential for phenology to make a difference in these and other areas.”

National impact

Over 500 groups have contributed phenology observations to Nature’s Notebook, including National Parks and Wildlife Refuges, Audubon chapters, Long-Term Ecological Research (LTER) sites, botanical gardens and arboretums, nature centers, universities, and the National Ecological Observatory Network (NEON).

USA-NPN maps of spring leaf out and bloom are used by dozens of local and national weather channels each year to communicate whether their location is experiencing (or will experience) an unusually early or late spring in a particular year. USA-NPN Spring Index maps are also used by USDA Climate Hubs to understand potential planting delays.

USA-NPN data and data products have been used in the National Climate Assessment, EPA Indicators Report, and more. In fact, Crimmins is an author on the Ecosystems and Biodiversity chapter of the Fifth National Climate Assessment.

The National Ecological Observatory Network uses USA-NPN protocols for their plant phenology data collection; data are ingested into the National Phenology Database monthly by the USA-NPN and are available for visualization and download. USA-NPN has also been funded by USDA Climate Hubs to develop a forecast for winter wheat to predict when wheat is susceptible to frost damage.

USA-NPN’s forecasts of activity of insect pest and invasive plants, which help managers know when to time treatment activities, have been used by the National Park Service, US Forest Service, multiple extension programs across the country, as well as private arborists.

Supporting local phenology programs

The 30 millionth observation was made by a member of the Desert View High School Local Phenology Program in Tucson, AZ. Nika Gonzaga, a freshman honors biology student, submitted the observation of young leaves on desert willow.

"As a freshman, this is my first time ever gathering research like this,” Gonzaga said. “It was enjoyable and a very simple task. I hope to do more research on other plants."

“My students enjoy taking a break from the classroom and going outside to the Phenology Trail we have on our high school campus,” said Gonzaga’s honors biology teacher Cynthia Uber. “They love using the Nature’s Notebook app as it makes reporting their observations easier and quicker. We are using the data to see how climate change is affecting the species we have on our campus.”

Students on the UArizona campus also contribute to the program. Hayley Limes, an undergraduate student completing her degree in Environmental Science, has worked with the USA-NPN for the past two years through the NASA Space Grant Program. While working at the USA-NPN, Limes has written code to analyze flowering and fruiting timing data relating to important nectar plants for pollinators, expanding her skills in both programming and handling large datasets.

"Working with the USA-NPN has really increased my understanding of how plants and pollinators interact. I'm excited to continue to learn about all the ways phenology observations can be used."

Multiple graduate students in the College of Public Health, advised by Kacey Ernst, have completed internships with the USA-NPN to help the network better understand how phenology can help data gaps in public health research. For example, students have worked with USA-NPN staff to contact epidemiologists and vector control staff across the country to understand their needs for forecasts of mosquito seasonal activity. This work has helped to define what a mosquito activity forecast and notification service could look like for those working to control vector-borne diseases.

Elizabeth Vogt, a graduate student mastering in public health, has been exploring the potential for observations of flowering contributed to Nature’s Notebook to address a significant gap in pollen monitoring across the nation. A clearer picture of when various allergenic plants are releasing pollen has the potential to support allergy and asthma management in a significant way.

Getting involved in Arizona

There are a number of campaigns underway in Southern Arizona that offer folks an opportunity to get involved and help researchers better understand invasive species and gather data to serve conservation efforts.

Invasive buffelgrass

Volunteers are collecting weekly observations across Tucson on when buffelgrass greens up and how long before it goes to seed to improve guidance for managers on where and when to spray herbicides.

“I love the diverse flora and fauna of the Sonoran Desert, and we need to learn how to control invasive buffelgrass so that it doesn’t wipe out this diversity,” said Jan Schwartz, Arizona Master Naturalist. “My hope is that the data I collect at Tucson's Mission Garden will inform managers of exactly when to remove buffelgrass.”

Nectar-feeding bats

Volunteers are collecting flowering data on saguaros and agaves across Southeastern Arizona to inform the USFWS about where and when nectar is available for migrating bats while they are in Arizona.

“The NPN provides us with up-to-date and cutting edge information to inform the work we do to conserve and recover species,” said Scott Richardson, Supervisory Biologist for the United States Fish and Wildlife Service. “By partnering with NPN, we have access to greater quantities of information covering a broader geographic scope that would be possible on our own.”


Volunteers are collecting data on monarch and milkweed phenology across Arizona. The USA NPN are working with the Desert Botanical Garden in Phoenix to better understand monarch overwintering behavior and whether monarchs are breeding during the winter months in Arizona.


Rosemary Brandt
Director External Communications
Extra Info
Extra Info

Learn more about the USA National Phenology Network and ways you can get invoved.