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Interagency Whitebark Pine Monitoring Program in the Greater Yellowstone Ecosystem - Overview

Sapling grows at the base of a whitebark pine snag in the high mountains.
Whitebark pine snag creates a microsite for smaller surviving cohorts, Green River Lakes, Bridger-Teton National Forest, Wyoming, 2023

NPS/Shanahan

This article begins the article series, Whitebark Pine Monitoring in the Greater Yellowstone Ecosystem.

Whitebark pine (Pinus albicaulis) is an iconic species of subalpine forests. In these mountainous environments, it is a keystone species, playing a critical role in ecosystem dynamics by regulating many ecological processes and influencing biodiversity (Tomback and Kendall 2001; Ellison et al. 2005). Whitebark pine is also considered a “pioneer” species due to its tolerance of harsh environmental conditions and ability to establish and persist where other species cannot. In doing so, whitebark pine can alter the microclimate and enable species such as subalpine fir (Abies lasiocarpa) to establish in these otherwise inhospitable regions (Tomback et al. 1993). Although whitebark pine has very little commercial value, its seeds provide seasonal forage for a variety of wildlife, including grizzly bears (Ursus arctos horribilis), red squirrels (Tamiasciurus hudsonicus), Clark’s nutcrackers (Nucifraga columbiana), and a variety of granivorous small mammals. Whitebark pine is one of two “five-needle pine” species in the Greater Yellowstone Ecosystem, the other being limber pine (Pinus flexilis).

High-elevation forests throughout the American West have experienced significant changes in composition and structure over the past 50 years (Logan et al. 2009; Westerling et al. 2011; Keane et al. 2012), and whitebark pine is no exception. Whitebark pine populations have experienced declines due to several factors: 1) white pine blister rust (blister rust) caused by an introduced fungus, Cronartium ribicola, 2) native mountain pine beetle (Dendroctonus ponderosae), 3) wildland fire, and 4) climate change. Blister rust has proliferated throughout its range, impacting whitebark pinecone production and damaging young trees (Tomback et al. 1995). In the last century, blister rust has resulted in significant whitebark pine mortality in the Pacific Northwest and parts of the northern Rockies (Arno 1986). Between 2000 and 2010 widespread infestations of mountain pine beetle in high elevation stands have killed expansive swaths of mature whitebark pine forest (Logan et al. 2009). In the Greater Yellowstone Ecosystem (GYE) the combination of blister rust damage and mortality from mountain pine beetles has shifted whitebark pine populations to smaller sized trees and threatened whitebark pine reproduction and overall survival (Shanahan et al. 2016). Furthermore, fire regimes, which have historically been important for whitebark pine persistence, are becoming more frequent and increasing in intensity as snowpack melts earlier and faster due to rising temperatures (Westerling et al. 2011).

The loss of a foundational tree species such as whitebark pine has the potential to cause major changes in biological diversity and possibly trigger irreversible shifts in community composition and structure (Ebenman and Jonsson 2005). For these reasons, the persistence of whitebark pine across its historical range is of great concern. As a result, the U.S. Fish and Wildlife Service listed the whitebark pine as Threatened under the Endangered Species Act on January 17, 2023. Whitebark pine is considered Endangered in Canada (circa 2012).

Long-term monitoring of whitebark pine as a vital sign in the GYE is essential for understanding contemporary trends in disease, insect infestation, and whitebark pine regeneration. This information helps guide management decisions and actions into the future. Under the auspices of the Greater Yellowstone Coordinating Committee (GYCC), the National Park Service (NPS) Inventory and Monitoring Division (Greater Yellowstone Network) and several other agencies initiated a collaborative, long-term monitoring program to track and document the health status of whitebark pine across the GYE. This alliance resulted in the formation of the Greater Yellowstone Whitebark Pine Monitoring Working Group (GYWPMWG), which consists of representatives from the NPS, U.S. Forest Service (USFS), U.S. Geological Survey, Bureau of Land Management (BLM), and Montana State University. Since 2004, the Greater Yellowstone Network has spearheaded this multiagency whitebark pine monitoring program on NPS and U.S. Forest Service lands.

As a basis for this cross-jurisdictional monitoring program, the working group developed a protocol between 2004 and 2007 for monitoring the health status of the whitebark pine population in the GYE. After rigorous peer review, the Interagency Whitebark Pine Monitoring Protocol for the Greater Yellowstone Ecosystem was approved in 2007 and updated in 2011 (GYWPMWG 2011). Find the complete protocol on the Greater Yellowstone Network website.

In 2013, the Wyoming BLM began monitoring whitebark pine and limber pine on mapped stands of five-needle pines (Shanahan et al. 2022). Expanding monitoring to these areas provides more contiguous and inclusive information for evaluating the overall health of five-needle pine species in the region. However, data from five-needle pine monitoring on Wyoming BLM lands are not included in the data summary articles (2–4) of this article series, which are specific to whitebark pine populations on NPS and USFS lands. Find results from the five-needle pine monitoring program in the NPS.gov article series, Five-Needle Pine Monitoring on Wyoming Bureau of Land Management Forests in the Greater Yellowstone Ecosystem.

Long-term Monitoring Objectives

The objectives of the GYE interagency whitebark pine monitoring program aim to answer two questions that will help land managers understand and act to protect the health of whitebark pine in the GYE:

  • Is white pine blister rust increasing in the GYE?

  • Is the resulting mortality of whitebark pine sufficient to warrant consideration of management intervention, such as active protection and/or restoration?

Objective 1 – Estimate the proportion of whitebark pine trees more than 1.4 meters (>1.4 m) tall infected with white pine blister rust, and estimate the rate at which infection of trees is changing over time.

Objective 2 – Within infected transects, determine the relative severity of infection in whitebark pine trees >1.4 m tall (as indicated by aecia or canker location) and estimate the change in severity over time.

Objective 3 – Estimate survival of individual whitebark pine trees >1.4 m tall, explicitly accounting for the effects of white pine blister rust infection, mountain pine beetle activity, and wildfire.

Objective 4 –Document the recruitment of whitebark pine into the reproductive population and assess the multiple factors that influence overall recruitment success over time.

As we learn more about the dynamic nature of the multiple biotic and abiotic conditions impacting whitebark pine in the GYE, our analysis techniques and data collection procedures will remain adaptable as novel situations arise to meet contemporary management needs.

Articles 2 to 4 in this article series present monitoring results for each of the four individual objectives. Article 5 describes methods. Article 6 describes whitebark pine protection and restoration efforts.

Map of the Greater Yellowstone Ecosystem, with agency boundaries, showing national park lands surrounded by several different forest lands.
The Greater Yellowstone Ecosystem includes three national parks, five national forests, and Bureau of Land Management lands.

NPS

Part of a series of articles titled Whitebark Pine Monitoring in the Greater Yellowstone Ecosystem.

Next: White Pine Blister Rust Infection in Whitebark Pine in the Greater Yellowstone Ecosystem – Data Summary of Monitoring in 2023

Last updated: June 25, 2024