Friday, November 26, 2021

Whitebark Pine Considered for Threatened Species Status – the Impacts of a Changing Climate

As of 2016, more than half of all standing whitebark pines in the American West are dead

Dotting mountain ranges throughout the western United States and into Canada, the whitebark pine is a beloved tree by many who have walked beneath it during high altitude treks. With climate change, ecological threats like the mountain pine beetle and blister bark fungus have impacted many of the trees, leading it to be considered for threatened species status under the U.S. Endangered Species Act (ESA). 

The tree is slow-growing and short with gnarled branches that twist and extend toward the sky, shaped by winds that pummel it at the subalpine elevations it lives. The pine can be found in places as high as 10,000 feet and marks the top of the treeline on a mountain range before the topography changes to loose rock at the summit.

The whitebark pine is a keystone species that determines the health of the ecosystem. “It’s really an important tree at high elevations. It maintains snowpack, regulates runoff, and prevents erosion,” said Kimiora Ward, a plant ecology manager who has conducted research on the whitebark pine in Yosemite National Park. 

It also has a symbiotic relationship with several animals, including the Clark’s nutcracker, a chatty bird in the crow family that cracks open whitebark pine cones and caches the seeds to eat in the future. 

“The primary way [whitebark pine] seeds are dispersed is through nutcrackers spreading the seeds,” said Ward. “When they forget where they’ve cached seeds, they’re essentially planting a new tree.”  

In recent decades, warming temperatures have increased the threats to the whitebark pine. According to a U.S. Fish & Wildlife press release from December 2020, due to blister rust, mountain pine beetles, and tougher wildfire seasons, 51 percent of all standing whitebark pines in the American West are dead, as of 2016. 

The resistant skeletons of whitebark pine trees hold on at high elevations in Glacier National Park. Possibly decades earlier, they succumbed to either white pine blister rust or mountain pine beetles – photo: National Park Service

For blister rust, a fungus that chokes a tree’s branches and deprives it of water and nutrients, its range has changed as temperatures get warmer at higher elevations. A 2021 UC Davis study found that the prevalence of blister rust at high subalpine elevations has increased by 7 percent. This includes regions where whitebark pine can be found.

Similar to the way blister rust’s range has changed with climate change, mountain pine beetle prevalence has also changed. Usually, large parts of the mountain pine beetle population are killed due to cold in the winter months, but this has changed as warmer winters keep this mortality rate low, according to the U.S. Forest Service. Once allowed to take year-round hold of a tree, the effects can be deadly. 

Fortunately, in much of the Sierra and through Yosemite National Park, whitebark pines have been largely unaffected by these threats, research has found.

“Our preliminary findings have shown that Yosemite is doing pretty well,” said Frank Dean, president of the Yosemite Conservancy. The Conservancy provides funding to the park to conduct research on the tree’s health. 

It is common to find mature whitebark pine trees well over 400 years of age as seen in this image, especially on harsh growing sites – photo: U.S. Forest Service

However, for the trees that have not been so lucky in the Cascades, Rockies, and Pacific Coast mountain ranges, these threats have been more severe. The whitebark pine has been a candidate for listing as threatened under the ESA since 2011, and in December of 2020, the U.S. Fish & Wildlife Service (USFWS) published a proposed rule to list the species. Public comment on the proposal closed in January of 2021, and on February 5, recommendations for proposed federal actions affecting the whitebark pine were published. To date, these are the only steps that have been made to list the tree. 

If the whitebark pine does receive protection under the ESA, removal of whitebark pines on public lands and removal for interstate or foreign commerce would be prohibited, as stated in the USFWS December press release. Restoration and research would still be allowed, which includes activities like seed banking and plant propagation.

“In much of the range, land managers are collecting seeds and screening them for blister rust resistance. When they find resistance, they propagate seedlings from resistant trees and plant these seedlings on the landscape so you have greater resilience in the regenerating stands of younger pines,” said Yosemite ecology manager Kimiora Ward. By doing this, land managers can help the species build better defense mechanisms to ecological threats.

According to the National Oceanic and Atmospheric Administration (NOAA), the final ruling for listing a species is usually published within one year of the proposed rule, but this time frame can be extended depending on various circumstances. For the whitebark pine, a ruling date is unknown but expected by the end of the year.



Top photo caption and credit: A whitebark pine (Pinus albicaulis) in Crater Lake National Park – photo: National Park Service/Jen Hooke


Claire Carlson writes about the environment for the Ally. Support her work.