USA NPN National Phenology Network

Taking the Pulse of Our Planet

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Photo of USA-NPN staff in 2022

USA-NPN National Coordinating Office staff in October 2022. 


The USA-NPN's National Coordinating Office (NCO) guides the development of the Network, facilitates communication between scientists, land managers, policy-makers, and the public who are interested in assessing the effects of global change on natural ecological systems. Staff members are employees of The University of Arizona.

Theresa Crimmins

Theresa Crimmins 
(520) 621-8523
Short CV

Theresa Crimmins is the Director for the USA National Phenology Network and has been a part of the organization since 2007. Hailing from Ohio and Michigan, she received a B.S. and M.A at Western Michigan University and a Ph.D. from the University of Arizona. In her role with the Network, Theresa supports an amazing team of individuals and works enthusiastically to support the growth and use of phenology data and resources curated by the USA-NPN, involvement in Nature’s Notebook, and a broader appreciation of phenology among scientists and non-scientists alike.

Theresa is also a Research Professor in the School of Natural Resources and the Environment at the University of Arizona and has published over 70 peer-reviewed articles and book chapters in journals including Nature, Geophysical Research Letters, Global Change Biology, and Journal of Ecology. Her writing has also appeared in Scientific American, The Hill, and the Arizona Daily Star, and she has appeared in the PBS productions SciGirls and American Spring Live as well as on NPR and The Weather Channel. Theresa is an author on the Ecosystems and Biodiversity chapter of the Fifth National Climate Assessment, is a member of the inaugural cohort of NEON Ambassadors, and is a Fellow of the Linnean Society. She also currently serves on the editorial board for Ecosphere. In 2018, Theresa received the Alumni Achievement Award from the Department of Geography as well as the Globally-Engaged Pillar Award from the College of Arts and Sciences at Western Michigan University.

Nathan AcostaNathan Acosta staff photo
Web Developer

Nathan works on development, enhancement, and maintenance of the USA-NPN's web platforms. His duties mostly involve working on USA-NPN's websites making sure they function smoothly and are able to meet researcher's and observer's needs. He works closely with the rest of the team to make sure all aspects of the IT infrastructure work as intended and efficiently as possible.

Nathan graduated from The University of Arizona and got a B.S. in Computer Science with an Informatics minor and an Undergraduate Certificate in Cyber Security. He grew up in Arizona's neighboring state of Sonora, Mexico and he is passionate about researching and preserving the immense biodiversity of the Sonoran Desert. When he's away from the keyboard he likes to learn new cooking recipes, play the piano, and spend time with his family and dogs.

Samantha BrewerSamantha Brewer
Volunteer Engagement Coordinator

Samantha Brewer communicates with new and existing Nature’s Notebook observers and organizations through engaging activities, newsletters, campaigns, and training materials. She coordinates with Local Phenology Leaders to strengthen their programs and assist in volunteer recruitment and retention strategies. She also works to identify communities that are underrepresented in the scientific field and offers guidance for them to develop their own Local Phenology Programs that fit the needs of their organizations and produce quality data. Samantha helps lead the Local Phenology Leader Certification Course, and supports the Local Phenology Leader Community of Practice.

Samantha earned her Bachelor’s and Master’s degrees in biology at Northern Arizona University. She has worked across the state of Arizona studying avian ecology, with her Master’s thesis focusing on Gray Hawk population changes along the San Pedro River. She also has a background in Education - teaching biology and ecology at both the college level and K-12 settings. Prior to working for the USA-NPN, she worked as an Educator and Certified Local Phenology Leader for the Reid Park Zoo in Tucson. In her free time, she loves cross-stitching, gaming, and running along The Loop trail. 

Ellen DennyEllen Denny
Monitoring Design & Data Coordinator
Short CV

Ellen Denny coordinates the development of the USA-NPN protocols for the collection of standardized ground-based plant and animal phenology observations across the nation.  She also serves as a scientific data manager for the National Phenology Database, and as a global liason, helping to advise developing national phenology networks around the world, and working towards global integration of phenology data.
Ellen has a B.S. in Aquatic Biology from Brown University, and an M.F.S. (Forest Science) from the Yale School of Forestry & Environmental Studies. Her professional interests began in marine invertebrate ecology, shifted to ecological restoration, and eventually landed in terrestrial ecosystem ecology. She spent a decade working as a field ecologist and data manager in the forests of New England before coming to the USA-NPN in 2008. Ellen lives in Kittery, Maine, and participates remotely in the Tucson-based National Coordinating Office.

Erin Posthumus

Erin Posthumus
Outreach Coordinator and US Fish & Wildlife Service Liaison
(520) 314-7883
Short CV

Erin Posthumus coordinates outreach and communication efforts for the USA-NPN and Nature's Notebook. She is also the USA-NPN's liaison to the US Fish & Wildlife Service and is working with National Wildlife Refuges across the country to implement phenology monitoring to meet their resource management goals.

Erin received her B.A. in Environmental Biology from the University of Colorado at Boulder, then worked on a variety of field biology projects around the US and abroad. She first came to the USA-NPN as a Peace Corps Fellow in 2010, during her graduate program at the University of Arizona's School of Natural Resources and the Environment. In 2013 she was awarded a Master of Science for her research on wildlife species diversity at endangered red squirrel middens. 

Alyssa RosemartinAlyssa Rosemartin 
Partner & Application Specialist
Short CV

Alyssa Rosemartin supports partnerships with resource management agencies and researchers to advance the USA National Phenology Network's mission to improve scientific understand and decision-making. She also contributes to in-house data product development, including quality control.

Alyssa has twenty years of experience working in the field of natural resources, in IT, research, education and project management.  Alyssa received a B.A. in Spanish and environmental science in 2000 from Smith College and an M.S. in wildlife conservation and management from the University of Arizona's School of Natural Resources and the Environment in 2008. Her thesis explores the relationship between food availability and reproductive investment in terns, as well as breeding bird use of wetlands in the northern Gulf of California.

Jeff SwitzerJeff Switzer
Systems Analyst
(520) 621-1636

Jeff Switzer will be using his programming skills to enhance and debug all aspects of the USA-NPN's IT infrastructure. His duties range from solving problems with the mobile apps to creating features for the website to optimizing the database. He assists the USA-NPN team in making processes and functionalities more efficient and more adept to handling observer’s needs.  

Jeff graduated from the University of Wyoming with B.S. degrees in computer science and mathematics. As a graduate student, he researched resource-bounded dimension and joined a startup where he developed an electronic medical records system. He then spent two years teaching in Africa before joining the NPN team. When he's not coding you can find him camping, mountain biking, making music, and drinking tea.

Collaborators, post-docs, and students

Carla ArreguínCarla Arreguin staff photo
Visiting Intern

Carla Arreguin is an undergraduate student from Mexico City in an internship program with the USA-NPN. She is pursuing her Bachelor’s degree in Geography at the Universidad Nacional Autónoma de México, and is currently doing her thesis project in the impacts of climate and land use change in species of fireflies. She has always been interested in the environment and biodiversity, and how they are affected by human activities. One of her main goals is to gain experience in habitat and environmental management to help preserve biodiversity, and communities that depend on natural resources. Beyond the academic world, she likes to read, draw, and be with her two old small doggies.

Viviana BeltranViviana Beltran staff photo

Viviana Beltran, originally from San Luis, AZ, has always had a passion for STEM educational outreach in underrepresented communities such as her hometown. She received her Bachelor's in environmental science in 2021 and is currently a graduate student at the University of Arizona studying educational psychology to bridge the gap between environmental science knowledge and educational community outreach. Viviana's future goals involve improving her public science communication and getting more experience working with underrepresented communities. She is very excited to work with USA-NPN as a student translator and find ways to make Nature’s Notebook more accessible to different underrepresented communities!

Tanner BlandTanner Bland
Student Administrative Associate

Tanner Bland is an undergraduate at the University of Arizona, with a double major in Ecology and Evolutionary biology and Bioinformatics, with an interest in restoration ecology and entomology. 

Tanner is a part of the UA Game and Fish Society and Tucson Bee Collaborative. He is currently helping to assess the native biodiversity of bees in the Sonoran Desert. Outside of school he loves to cook with his family and hike.

Sofia Guadalupe DelgadoSofia Guadalupe Delgado, NASA Space Grant Intern, profile picture
NASA Space Grant Intern

Sofia Guadalupe Delgado is an undergraduate at the University of Arizona pursuing a Bachelor's degree in Ecology and Evolutionary Biology and is a current NASA Space Grant intern. Sofia is originally from El Paso, Texas, and is interested in the American Southwest desert that surrounds them. Outside of school, Sofia enjoys painting, drawing, and being a giant nerd.

Ava LasaterAva Lasater

Ava Lasater is an undergraduate student at the University of Arizona majoring in Bioinformatics and is in the Honors College. Ava is from Golden, Colorado, and is interested in climate change and how changes in the environment and ecology affect human health.

She is looking forward to getting involved on campus over the course of the year, specifically with volunteering and clubs in addition to research.