Spring Starting Earlier in 75% of National Parks Studied
Climate change impacts to parks are already costly and hard to manage, according to findings by a team including UA scientists.

UA College of Agriculture and Life Sciences
Oct. 6, 2016

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An observer in the Sonoran Desert records spring flowering phenology in an ocotillo.
An observer in the Sonoran Desert records spring flowering phenology in an ocotillo. (Photo: Brian Forbes Powell)

National parks in Arizona and across the country are seeing earlier springs driven by climate change, according to new research conducted by a team of scientists from the University of Arizona, the United States Geological Survey and the National Park Service.

Compared with historical average conditions, the change is happening earlier in three out of every four parks examined, and more than half the parks included in the analysis are experiencing extreme early onsets of spring. 

Published Oct. 6 in a special feature of Ecosphere called "Science for Our National Parks' Second Century," the study examined patterns of historical temperatures for 276 of the 413 national parks, including sites from Alaska to Florida. The study analysis spanned 1901 to 2012, a period that provides the best historical temperature data and overlaps the history of the National Park System. 

"Our challenge in real time is planning for and adapting to these changes — like the need to address increasing threats of invasive species, stresses on native species and changing visitor patterns driven by warmer weather," U.S. Secretary of the Interior Sally Jewell said in a statement released Thursday.  "It's clear that one of the biggest challenges our national parks face in their second century will be adaptive management in the face of a changing climate."

As the National Park Service embarks on its second century of stewardship, it is committed to understanding the causes and consequences of climate change for the parks and biological treasures they protect. A key partner in this endeavor is the USA National Phenology Network, or USA-NPN, hosted by the UA's School of Natural Resources and the Environment in the College of Agriculture and Life Sciences and funded by the United States Geological Survey. 

The USA-NPN engages researchers, decision makers and the public in understanding how climate change is impacting the timing of plant and animal life cycle events, known as phenology. The School of Natural Resources and the Environment staff, working for the USA-NPN, has supported the NPS in understanding phenological change since 2009, and brought together the collaborators and data for the study. 

The study leverages a set of climate change indicators, co-developed by the USA-NPN, called the spring indices — models based on nationwide field observations of first leaf-out and first bloom dates in two common and widely distributed flowering plants, lilac and honeysuckle. Using the indices, the authors calculated annual dates for the onset of spring in each park and analyzed those trends over the 112-year period. 

At the iconic Grand Canyon National Park, the study found that recent springs are happening earlier than 90 percent of historic springs. Educators and managers at the park have already taken note, and have engaged visitors in observing the phenology of key species, including the Gambel oak and Fremont cottonwood, since 2013. 

"These results provide a key long-term perspective on change across the National Park Service," said School of Natural Resources and the Environment research scientist Katharine Gerst, a co-author on the study.

"In addition to this study, we are working with 25 parks across the country to collect and analyze observational data in order to understand how seasons are changing," Gerst said. "We are finding complex responses, particularly in the Southwest, where the timing of rain and snow have a big effect on leafing and flowering." 

Co-author Jake Weltzin, executive director of the USA-NPN and an ecologist with United States Geological Survey, said: "The bottom line is not just that parks are susceptible to change. In fact, they have already changed. Many park managers are already managing in an extreme environment." 

In some cases, the early onset of spring has thrown off the timing of popular park events, such as the annual Cherry Blossom Festival on the National Mall in Washington, D.C. Studies suggest it also is disrupting critically important natural relationships, such as the link between the peak bloom of wildflowers and the arrival of birds, bees and butterflies that feed on and pollinate the flowers. 

Spring's early and sometimes unpredictable onset can lead to costly management issues that are difficult to plan for. Warm weather often gives a head start to invasive plants, many of which can leaf out quickly. Some park managers struggle to start weed control earlier in the season. 

"We used to be able to hire college students for that work," said Abraham Miller-Rushing, science coordinator at Acadia National Park in Maine, "but now they are still in school when we need them on the ground."

To help managers understand spring as it unfolds, the USA-NPN recently released national maps of the spring indices, including a six-day forecast of the arrival of spring and information about how spring this year compares to the 30-year average. 

"We are just beginning to understand the many implications of earlier springs," said study co-author Alyssa Rosemartin, partner and application specialist with the UA School of Natural Resources and the Environment. "We hope that people will join us in documenting changes in their area through participation in Nature's Notebook, the USA-NPN's phenology observation program." 

Extra info

The study is published in Ecosphere's "Science for Our National Parks' Second Century." For more information, visit:

  • U.S. Secretary of the Interior Sally Jewell's announcement of the new study
  • The published article
  • The U.S. Department of the Interior's site


Resources for the media

Alyssa Rosemartin 

UA School of Natural Resources and the Environment



Jake Weltzin

USA National Phenology Network at the UA