Understanding Dynamic Ecosystems: The Pursuit of the Greater Yellowstone Network

biologists doing climate change research in alpine environment
In 2016, a field crew collects alpine vegetation data at the long-term monitoring site located in the Absaroka Range along the east boundary of Yellowstone National Park. We study how plants, soils, and climate data change over time in order to understand how alpine areas are responding to change.

Understanding Dynamic Ecosystems: The Pursuit of the Greater Yellowstone Network

by Kristin Legg & Sarah Haas

We cannot protect what we do not understand.
— NPS Natural Resource Challenge, 1999

Who Are We?
The year 1999 was a pivotal year for the National Park Service (NPS). Inspired by the book Preserving Nature in the National Parks: A History (Sellars 1997), the Natural Resource Challenge (NPS 1999) was crafted to expand the NPS’s understanding and management of park natural resources. One of the more innovative outcomes of the Natural Resource Challenge was the creation of the NPS Inventory and Monitoring (I&M) Program. The overall mission of this program was to first establish a baseline inventory of park natural resources (What do we have?) and second, to provide scientifically sound information on how select resources are changing through time (How are parks doing?). This ongoing program is intended to provide the scientific basis for knowledge, management, and education about park resources and a view of the park ecosystems not previously available (Fancy et al. 2009). The I&M Program’s natural resource targets are intentionally wide ranging to include focal species (e.g., whitebark pine), taxonomic groups (e.g., bats, amphibians, birds), physical resources (e.g., water quality and quantity), natural ecosystems and associated communities (e.g., caves, marine areas, forests), and environmental drivers (e.g., climate).

The architects of this program recognized the benefit of grouping parks that are similar ecologically and geographically near one another, so that teams of NPS scientists, park managers, and partners could develop rigorous and relevant multi-park, long-term monitoring programs. As a result, 32 ecoregional networks were created to support over 280 parks with diverse and significant natural resources. As envisioned, each network collaborates among a group of parks to implement actions and take advantage of economies of scale. The Greater Yellowstone Network (GRYN), one of the 32 networks, is comprised of Bighorn Canyon National Recreation Area, Grand Teton and Yellowstone national parks, and the John D. Rockefeller, Jr., Memorial Parkway.

mariposa lily
Mariposa Lily with a visitor.

NPS Photo - D. Renkin

What Do We Have?

Similar to the other networks, the GRYN initially focused on baseline inventories of 12 targeted natural resource categories (e.g., air quality, water resources, vertebrate and plant species, geologic processes and features, soil resources, etc.). These inventories have been useful in advancing the parks' and the public's understanding of species present, as well as the state of air and watershed quality, among other resources. These inventories also serve as a foundation for how future changes to a park may affect long-term conservation of critical resources. These baseline inventories were used to inform the vital signs selected for long-term monitoring—the second phase of the network goals (see “Vital Sign Monitoring is Good Medicine for Parks,” this issue, for the definition of “vital signs”).

How to Select a Vital Sign?

It is a daunting task to select just a few of a park’s diverse natural resources to study long into the future. Working in collaboration, the GRYN, park managers, scientists, and partners prioritized natural resources using three criteria: ecological significance, management significance, and legal or policy mandates as directed from Congress or other legislation (Fancy et al. 2009). While staying true to the concept of an ecological network, GRYN and collaborators selected a subset of 48 identified vital signs for long-term monitoring (Jean et al. 2005). Yellowstone staff monitor at least 27 of the identified vital signs, including trumpeter swans, earthquakes, ungulates, raptors, and native fish. The GRYN focuses on seven vital signs based on what can realistically be monitored annually, while maintaining the necessary rigor required to reliably detect temporal change.

Another visionary part of the I&M Program is the emphasis placed on data stewardship and information sharing, critical components of long-term environmental monitoring that maximizes utility and learning (Lovett et al. 2007, Fancy et al. 2009). The value of long-term monitoring data is often under-appreciated initially, but its importance is later realized years down the road. Valuable and notable records include century-old weather station data collected by park managers, which are now used to help understand how climate is changing in the parks. By integrating weather data with monitoring data of small mammal populations in Yosemite National Park, park managers learned that small mammals had shifted upward in elevation in response to warming temperatures (Moritz 2007). Long-term monitoring can also help us anticipate and prepare for future changes to park ecosystems. For example, the monitoring of CO2 concentrations a top Hawaii’s Mauna Loa volcano has proven invaluable in numerous ways, but principally in connecting global temperature changes to rising CO2 levels. When this monitoring was initiated, there was no way to know it would someday serve as one of the most valuable scientific geophysical records ever collected. Over 60 years later, the “Keeling Curve” is a vital sign for Earth health (Keeling 2008; Imagine what scientists of the future will learn from the vital sign records collected in the parks today.

To help us oversee these important data, each park vital sign has a scientifically designed protocol, or recipe, that describes the collection, stewardship, analysis, and reporting of data needed to meet targeted objectives and ensure long-term consistency over time. The emphasis on data management and use of scientific protocols is one of the program’s greatest strengths in ensuring that we can provide timely, high quality science to parks and the public. Results are used to inform management decisions and lead to a greater understanding of long-term or emerging trends in each park’s dynamic ecosystems.

How Are Parks Doing?

In partnership with the parks and partners, GRYN has contributed to park stewardship of natural resources since 2000. For example, timely and targeted water quality monitoring informed the Montana Department of Environmental Quality that Soda Butte Creek, a tributary to the Lamar River in the northeast corner of Yellowstone National Park (YNP), could be removed from the list of impaired waters (i.e., 303(d) list) following the reclamation of an abandoned mill and tailings site (Henderson et al. 2018). The status and trends of whitebark pine across the Greater Yellowstone Ecosystem (“An Uncertain Future: The Persistence of Whitebark Pine in the Greater Yellowstone Ecosystem,” this issue) has contributed to the region-wide whitebark pine conservation strategy (GYCCWPS 2011) and were informative for the U.S. Fish and Wildlife Services’ review of whitebark pine during a status assessment for the Endangered Species Act. The GYA whitebark pine monitoring program has also been held up nationally as a leading example of how to track whitebark pine and other five-needle pines. The amphibian and wetland monitoring program is one of the largest (geographically) and longest running monitoring campaigns in the western U.S. It is providing critical information to improve our understanding of amphibian population dynamics and their responses to climate-induced habitat loss (“Taking the Pulse of Wetlands: What Are We Learning From the Amphibian Vital Sign?,” this issue). We are integrating climate vital signs with biological indicators to better understand when changes in natural resource conditions should be anticipated (“Patterns of Primary Production and Ecological Drought in Yellowstone,” this issue). In partnership with YNP’s vegetation program, sagebrush and grassland monitoring will help inform the park on the health of sagebrush grasslands (see the next issue of Yellowstone Science focused on grazing). The Yellowstone Dashboard on the Climate Analyzer website ( offers managers and the public easy access to weather station and stream flow data. Importantly, this tool provides users information in formats that quickly supports year-to-year comparisons of ecosystem processes like snow cover and snow melt runoff. In addition, YNP relies on vital signs data to inform park planning and publications such as the annual Resources & Issues Handbook and the Vital Signs and State of the Park resources reports (YCR 2011, 2013, 2018). Researchers also frequently contact the network to collaborate on projects and access vital signs data to help answer questions on the park’s ecosystem health.

Yellowstone is not alone—NPS I&M networks across the country continue to demonstrate the value of long-term monitoring in parks. In the Pacific Islands, monitoring data helped determine where and when to remove crown of thorns sea stars that were threatening coral reefs (Brown et al. 2017). Monitoring of forests in dozens of eastern U.S. parks revealed significant differences in forest structure (e.g., older and larger trees, more standing dead material, and different disturbance dynamics) relative to surrounding forests (Miller et al. 2016). These articles were featured in a special issue of the scientific journal Ecosphere (Rodhouse et al. 2016) that highlighted inventory and monitoring science as part of the 2016 NPS Centennial.

After nearly two decades, the vision of those who led the 1999 Resource Challenge and advocated for natural resource inventories and vital signs monitoring in parks is being achieved in tangible ways. NPS I&M networks are helping to tell the stories of important ecosystem functions. In the GYA, the GRYN illuminated landscape-level change in whitebark pine stands, participated in efforts to steward the Soda Butte Creek watershed to better health, and improved our understanding of how environmental drivers like changing snowpack may result in fewer wetlands for amphibian breeding. Through the continued collaboration with park managers, scientists, partners, and the public, vital signs monitoring will support science-based decision making into the future, paramount to the long-term conservation of park resources.

Literature Cited

Brown, E.K., S.A. McKenna, S.C. Beavers, T. Clark, M. Gawel, and D.F. Raikow. 2017. Informing coral reef management decision at four U.S. National Parks in the Pacific using long-term monitoring data. Ecosphere 7(10):e01463.

Fancy, S.G., J.E. Gross, and S.L. Carter. 2009. Monitoring condition of natural resources in US National Parks. Environmental Monitoring and Assessment 151:161-174.

Greater Yellowstone Coordinating Committee Whitebark Pine Subcommittee (GYCCWPS). 2011. Whitebark pine strategy for the Greater Yellowstone Area. Greater Yellowstone Coordinating Committee, Bozeman, Montana, USA.

Henderson, T., A. Ray, P. Penoyer, A. Rodman, M. Levandowski, A. Yoder, S. Matolyak, M.B. Marks, and A. Coleman. 2018. Mine tailings reclamation project improves water quality in Yellowstone’s Soda Butte Creek. Park Science 34:9–21.

Jean, C., A.M. Schrag, R.E. Bennetts, R. Daley, E.A. Crowe, and S. O’Ney. 2005. Vital signs monitoring plan for the Greater Yellowstone Network. National Park Service, Greater Yellowstone Network, Bozeman, Montana, USA.

Keeling, R.F. 2008. Recording Earth’s vital signs. Science 319:1771–1772.

Lovett, G.M., D.A. Burns, C.T. Driscoll, J.C. Jenkins, M.J. Mitchell, L. Rustad, J.B. Shanley, G.E. Likens, and R. Haeuber. 2007. Who needs environmental monitoring? Frontiers in Ecology and the Environment 5:253–260.

Miller, K.M., F.W. Dieffenbach, J.P. Campbell, W.B. Cass, J.A. Comiskey, E.R. Matthews, B.J. McGill, B.R. Mitchell, S.J. Perles, S. Sanders, J.P. Schmit, S. Smith, and A.S. Weed. 2016. National parks in the eastern United States harbor important older forest structure compared with matrix forests. Ecosphere 7:e01404.

Moritz, C. 2007. Re-survey of the historic Grinnell-Storer vertebrate transect in Yosemite National Park, California. Department of Integrative Biology, University of California, Berkeley, California, USA.

National Park Service (NPS). 1999. Natural resource challenge: the National Park Service’s action plan for preserving natural resources. Department of the Interior, National Park Service, Washington, D.C., USA.

Rodhouse, T.J., C.J. Sergant, and E.W. Schweiger. 2016. Ecological monitoring and evidence-based decision making in America’s National Parks: highlights of the special feature. Ecosphere 7:e01608.

Sellars, R.W. 1997. Preserving nature in the National Parks: a history. Yale University Press, New Haven, Connecticut, USA.

Yellowstone Center for Resources (YCR). 2011. Yellowstone National Park: natural resource vital signs. YCR-2011-07. National Park Service, Mammoth Hot Springs, Wyoming, USA.

Yellowstone Center for Resources (YCR). 2013. Yellowstone National Park: natural and cultural resources vital signs. YCR-2013-03. National Park Service, Mammoth Hot Springs, Wyoming, USA.

Yellowstone Center for Resources (YCR). 2018. The state of Yellowstone vital signs and select park resources, 2017. YCR–2018–01. Yellowstone Center for Resources, Yellowstone National Park, Wyoming, USA.

While working in Yellowstone, Kristin Legg distinctly recalls hearing about the Inventory and Monitoring Program in 1999 and dreamt of being part of that program. This became a reality in 2010 when she became the program manager for the Greater Yellowstone Network. Prior, she was the Chief of Resource Management & Science at Zion and Bryce Canyon national parks and Pipestone National Monument. Kristin received an MS in Fish & Wildlife Management from Montana State University.

Sarah Haas is currently the Deputy Chief of Science & Resource Management at Grand Canyon National Park. She worked for several years in Yellowstone’s Center for Resources as the Science Program Coordinator, as well as Deputy Chief. Sarah has worked with a variety of species on the edge of existence and considers it her primary responsibility to promote the understanding and conservation of the biodiversity of our national park treasures.

Last updated: September 16, 2019