Article

Assessing the Ecological Health of the Greater Yellowstone Ecosystem

Figure 1. Map of the GYE showing land ownership.
Figure 1. Map of the GYE showing land ownership.

Assessing the Ecological Health of the Greater Yellowstone
Ecosystem

by Andrew M. Ray, David P. Thoma, Kristin L. Legg, David M. Diamond, & Andrew J. Hansen

Species declines and extinctions are occurring at rates that are unrivaled in human and geological history (Ceballos et al. 2017). Similarly, wild places are also dwindling in area (Watson et al. 2018). Some large, protected areas like the Greater Yellowstone Ecosystem (GYE; figure 1) have experienced less change than more populated corners of the world primarily because the GYE benefits from a substantial level of federal agency protection. This 22 million acre-ecosystem with Yellowstone National Park (YNP) at its core represents continuous essential habitat for sustaining a viable population of free-roaming grizzly bears (Craighead 1977).

In the GYE, nearly two-thirds of the lands are managed by federal agencies that use techniques designed to achieve or maintain public land health for the benefit of future generations. Coordinated, cross-boundary conservation efforts in the GYE have captured the attention of conservationists the world over. Grizzly bear populations have grown from approximately 150 in 1975 to over 700 bears today (van Manen et al. 2018). Wolves were reintroduced to YNP between 1995 and 1997; and despite higher human-caused mortality outside of the national park boundaries, wolves are now widespread throughout the GYE (Smith et al. 2016). Native fish restoration efforts are helping to protect cutthroat trout and grayling strongholds through targeted non-native species eradications (Koel et al. 2017), and states are helping to bring together public and private stakeholders to establish landmark protections for antelope, elk, and mule deer migration corridors (WYGFD 2016).

Despite these successes and the strategies used by land managers to maintain the health, diversity, and productivity of public lands, other stressors still loom large. Some of the threats are historic (e.g., legacy pollution from mining), but many, including climate change, exurban growth, increased recreation, invasive species, and wildlife disease represent modern stressors with limited historical influence for contemplating outcomes or mitigative actions (Hansen et al. 2014). Even on the most protected lands in the GYE, where human pressures have been quite modest (27.5% of the GYE is managed as wilderness), these external stressors have already contributed to significant changes including rising temperatures, changes in snowpack, and the introduction and expansion of invasive species. These changes have produced new mixtures of native and invasive species growing and living under new rules with rapidly changing environmental conditions. The collection of new conditions and species assemblages are typically referred to as novel ecosystems (Hobbs et al. 2006.)

On the private lands' portion of the GYE, land use, climate change, and invasive species are similarly pushing ecosystems towards unfamiliar conditions. Taken together, these documented changes and the anticipation of future conditions across the GYE will require shifts away from historical management approaches and towards novel management strategies and deliberate adaptation planning (e.g., Climate Smart Conservation and Scenario Planning; Stein et al. 2014). Understanding how to manage these new ecosystems, therefore, requires documentation of how conditions are changing.

To characterize the sometimes messy and individualized details of ecosystem change (Rodhouse et al. 2016), we need vital signs monitoring that is tailored to the specific needs of the region. An integrated, cross-organizational, GYE-wide vital signs monitoring and assessment program is essential for characterizing local and regional conditions (e.g., patterns in biological productivity at scale; figure 2) documenting past biological, chemical, and physical change, and to help us perceive problems before they become intractable. Documenting conditions is also a critical first step to contemplating whether traditional or novel management strategies will be needed to achieve management goals of desired future conditions (Seastedt et al. 2008, Truitt et al. 2015).

A regional framework already exists for monitoring a number of the GYE’s physical vital signs (e.g., Sepulveda et al. 2015, Al-Chokhachy et al. 2017). For example, weather conditions, snowpack depths, and river flows across the GYE are already being monitored through a network of stations that regularly transmit publicly available measurements. As a result, the monitoring of regional air temperatures, snowpacks, and river and stream flows (physical vital signs) can be readily summarized and compared against a historical backdrop. And as the country’s oldest national park, some of YNP’s vital sign records (e.g., air temperature and river flow data) in the GYE span the 20th century.

On the other hand, coordinated efforts to monitor non-game biological indicators at a comparable spatial scale are less common (grizzly bears and whitebark pine are notable exceptions). Scaling existing biological vital signs monitoring programs that are already underway in YNP and neighboring Grand Teton National Park (e.g., amphibians and bats) or developing protocols for monitoring species and taxonomic groups that are informally monitored (e.g., butterflies) or currently go unmonitored would require financial and personnel resources that currently do not exist. Despite these limitations, the need to track changes in abundance and distribution of biological indicators and, more generally, ecosystem health are widely embraced (Fancy et al. 2009, Rodhouse et al. 2016).

To add value to the monitoring data, it is important to analyze trends in ecological condition over recent decades and to project possible trends under plausible future scenarios. Such analyses allow for establishing if vital signs are improving relative to management objectives, are stable, or are deteriorating, thereby providing a basis for prioritizing management actions (Hansen and Phillips 2018). It is also important to effectively communicate these trends to the diverse stakeholders of the GYE so they have information to inform decision making about actions relevant to the health of the GYE.

In “Vital Signs Monitoring is Good Medicine for Parks,” this issue, we learned that knowledge gained through human health monitoring is beneficial for establishing individual baselines or reference points, supporting diagnoses, initiating medical interventions, surveilling diseases, and characterizing health responses to medical treatments. Comparable benefits can be achieved from monitoring ecosystem health, and the knowledge gained should support informed stewardship of GYE’s public and private lands.

A monitoring program with clearly defined objectives and statistically valid design offers clear benefits over more piecemeal or reactive data gathering activities (Lindenmayer and Likens 2018). For example, a regional monitoring program will help prioritize limited resources, identify solutions to the most pressing of the GYE’s ecological problems (e.g., connectivity, refugia, blister rust resistant trees), raise awareness of issues so they get needed attention, and offer a sharper understanding of the scale of the ecological impacts. In sum, a well-thought-out, well-planned monitoring program will ensure that the right actions can be implemented in the right place and at the right time.

We all have a stake in preserving and protecting YNP and surrounding public and private lands that constitute the GYE. Without information generated through monitoring, we have limited knowledge about how, where, and when conditions are changing. For a region recognized as one of Earth’s remaining intact wildlands, we argue that a greater understanding of the health of the GYE (gained through monitoring) is worth considering. The knowledge gained would, in turn, serve as essential underpinnings for future policy and a catalyst for public engagement (Brandt et al. 2014). Regardless of what management or adaptation strategies are ultimately adopted, a regional vital signs monitoring program will be an indispensable component of protecting and preserving YNP and the region (Hansen and Phillips 2018).

Literature Cited

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satellite image showing GYE boundaries
Figure 2. Satellite image of the GYE showing variations in vegetative productivity (i.e., greenness) across the ecosystem. The GYE boundary is shown in yellow and, for reference, the YNP boundary is shown in blue. Imagery is from the National Aeronautics and Space Administration (NASA).


Andrew Ray is an Ecologist with the National Park Service’s Greater Yellowstone Network. Andrew has a PhD from Idaho State University, MS from Northern Michigan University, and BS from Purdue University. He works on wetland and water quality monitoring projects in Grand Teton and Yellowstone national parks and Bighorn Canyon National Recreation Area.

David Thoma is a scientist with the National Park Service Inventory and Monitoring Program in Bozeman, MT. He uses a water balance model and satellite remote sensing to understand broad-scale relationships between climate and biology.

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.

David Diamond is the Executive Coordinator of the Greater Yellowstone Coordinating Committee (GYCC). Through the GYCC, federal land managers pursue voluntary opportunities to cooperate at the landscape scale (see https://www.fedgycc.org/). David's federal experience includes work with the National Park Service, National Oceanic and Atmospheric Administration, the U.S. Fish and Wildlife Service, and the Department of the Interior. David has a Master of Science in Environmental Science and Master of Public Administration from the School of Public & Environmental Affairs at Indiana University, and a bachelor's in environmental science and history from the University of Virginia.

Andrew Hansen is a Professor in the Ecology Department and Director of the Landscape Biodiversity Lab at Montana State University. He teaches macroecology to undergraduates and landscape ecology to graduate students. His research focuses on interactions among biodiversity, climate change, and land use, with an emphasis on large landscape management and protected areas. He received a Ph.D. in ecology at the University of Tennessee and the Oak Ridge National Laboratory. He was on the faculty of Oregon State University, where Dr. Hansen studied ecological approaches to forestry. Current research at Montana State University focus on sustaining wildland ecosystems under climate and land use change, with a focus on the US and eight countries in the humid tropics. This work uses a combination of remote sensing, spatial analysis, computer simulation and field studies. This research has been funded primarily by NASA, US Department of the Interior, Environmental Protection Agency, US Department of Agriculture, conservation organizations, and the timber industry. Dr Hansen currently is on the science leadership teams for the North Central Climate Science Center and the Montana Institute of Ecosystems. He is co-editor of the recent book, “Climate Change in Wildlands: Pioneering Approaches to Science and Management.


Andrew Ray is an Ecologist with the National Park Service’s Greater Yellowstone Network. Andrew has a PhD from Idaho State University, MS from Northern Michigan University, and BS from Purdue University. He works on wetland and water quality monitoring projects in Grand Teton and Yellowstone national parks and Bighorn Canyon National Recreation Area.

David Thoma is a scientist with the National Park Service Inventory and Monitoring Program in Bozeman, MT. He uses a water balance model and satellite remote sensing to understand broad-scale relationships between climate and biology.

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.

David Diamond is the Executive Coordinator of the Greater Yellowstone Coordinating Committee (GYCC). Through the GYCC, federal land managers pursue voluntary
opportunities to cooperate at the landscape scale (see https://www.fedgycc.org/). David's federal experience includes work with the National Park Service, National Oceanic and
Atmospheric Administration, the U.S. Fish and Wildlife Service, and the Department of the Interior. David has a Master of Science in Environmental Science and Master of Public
Administration from the School of Public & Environmental Affairs at Indiana University, and a bachelor's in environmental science and history from the University of Virginia.

Andrew Hansen is a Professor in the Ecology Department and Director of the Landscape Biodiversity Lab at Montana State University. He teaches macroecology to undergraduates and landscape ecology to graduate students. His research focuses on interactions among biodiversity, climate change, and land use, with an emphasis on large landscape management and protected areas. He received a Ph.D. in ecology at the University of Tennessee and the Oak Ridge National Laboratory. He was on the faculty of Oregon State
University, where Dr. Hansen studied ecological approaches to forestry. Current research at Montana State University focus on sustaining wildland ecosystems under climate and land
use change, with a focus on the US and eight countries in the humid tropics. This work uses a combination of remote sensing, spatial analysis, computer simulation and feld studies. This research has been funded primarily by NASA, US Department of the Interior, Environmental Protection Agency, US Department of Agriculture, conservation organizations, and the timber industry. Dr Hansen currently is on the science leadership teams for the North Central Climate Science Center and the Montana Institute of Ecosystems. He is co-editor of
the recent book, “Climate Change in Wildlands: Pioneering Approaches to Science and Management.

Last updated: September 16, 2019