It’s a slow-maturing tree that inhabits some of the most rugged, high-elevation places on the continent, but it depends on a mid-sized bird for regeneration. While fires create optimal growing conditions, high-intensity fires threaten its survival, as does blister rust (a fungus), pine beetles, and climate change.
Last week’s decision by the U.S. Fish & Wildlife Service (FWS) to grant Endangered Species Act protection to the whitebark pine as a threatened species puts the spotlight on the unique life history of this keystone tree species and the challenges to its recovery. And while federal law mandates recovery efforts, another federal law may hinder needed restoration efforts. To top it off, recovery efforts focused on whitebark pine may conflict with recovery of other federally protected species such as the Canada lynx.
Why It’s Unique
Whitebark pine is the only stone pine (referring to their stone-like seeds) in North America of the five species worldwide, according to FWS. The whitebark is a slow-growing, long-lived tree with a life span of between 500 years and 1,000 years, and favors high-elevation locations in areas without competition, such as those with an open canopy with low litter depth and high rock cover.
If those factors weren’t amazing enough, consider the whitebark’s mutualist relationship with a crow-sized bird, the Clark’s nutcracker. Whitebark pines require seed dispersal by Clark’s nutcrackers, and nutcrackers require whitebark pine seeds for food. Nutcrackers cache the seeds in the ground in the summer for consumption throughout winters. The seeds not used by seed predators (from squirrels to grizzly bears) may then germinate (a process that takes between 2 and 11 years), initiating the next generation of whitebark pine.
But it takes a very long time for a whitebark pine to produce seed cones, with an average age of 40 years at first cone production, and a large cone crop is usually not produced until a tree is 60-80 years old. A single nutcracker can cache up to an estimated 98,000 whitebark pine seeds during good seed crop years, according to FWS, and typically bury the seeds close to the parent tree, setting the stage for the slow process to begin.
Whitebark pine is a species that exhibits masting, in which years of high seed production are synchronized within a population every three to five years. According to FWS, “This masting strategy is an adaption to heavy seed predation; during masting years seed consumers are satiated, resulting in excess seeds that escape predation. Whitebark pine populations need a certain density of reproductive individuals to produce sufficient pollen clouds that facilitate the synchronization of masting, and thus increased probability of regeneration. Whitebark pine populations also need a certain density of reproductive individuals to attract Clark’s nutcrackers, which are almost exclusively the seed dispersal mechanism for whitebark pines.”
To Live and Die by Fire
FWS has identified four main stressors for whitebark pine: altered fire regimes, white pine blister rust (a disease caused by an introduced fungus), mountain pine beetle, and climate change, but its fire that the species both depends on and is threatened by. Fire creates sites that are suitable for the Clark’s nutcracker seed-caching behavior and that, most importantly, provide optimal growing conditions for whitebark pine seeds.
“Without regular disturbance, primarily from fire, these forest communities follow successional pathways that eventually lead to climax communities dominated by shade-tolerant conifers such as subalpine fir, Engelmann spruce, and mountain hemlock, to the exclusion of whitebark pine,” according to FWS. “Once shade-tolerant conifer species become firmly established, the habitat is effectively lost to whitebark pine until a disturbance like fire once again opens the area for whitebark pine regeneration.” Newly burned areas provide a seedbed for whitebark pine, “and if stands of unburned cone-producing whitebark pine are nearby (i.e., within the range of Clark’s nutcracker caching behavior), Clark’s nutcrackers will cache those seeds on the burned site, and regeneration is likely.”
While the tree needs fire to create optimal growing conditions, it also cannot survive high-severity fires in which all age and size classes can be killed. The spread of blister rust fungus and mountain pine beetles have caused poor stand health and reduced reproductive capacity so that regeneration of whitebark pine following high-severity fire is unlikely.
White pine blister rust remains the primary threat to whitebark pine, but as a result of all these stressors, scientists estimate that 51% of all standing whitebark pine trees are dead. A broad distribution of the species remains across more than 80 million acres in Washington, Oregon, California, Idaho, Montana, Wyoming, Nevada, and Canada. In the U.S., 88% of the species range is on federal land.
The FWS assessment for whitebark pine identified wilderness designations a primary challenge to restoration of this species. With 29% of its range within the United States designated or defacto wilderness areas, “This designation limits management options and conservation efforts in those areas to some degree,” according to the assessment. The assessment points to the Wilderness Act which generally does not allow for many direct restoration activities to occur in designated or recommended wilderness areas.
“The Wilderness Act states that wilderness should be managed to preserve its natural conditions and yet remain untrammeled by man, thus presenting a fundamental debate as to whether restoring whitebark pine in wilderness areas detracts from or enhances the wilderness character, and whether human intervention to restore potentially trammeled whitebark pine forests is a legally and socially acceptable pursuit,” the assessment stated. FWS pointed out that how the Wilderness Act is implemented can vary between agencies, regions, or even between species.
The agency asserts that the combined effects of the blister rust and fire-exclusion practices “have indirectly led to unnatural (i.e., trammeled) conditions in whitebark pine habitat, and though restoration activities in wilderness areas may lead to short-term trammeling effects, the long-term payoff may be a return of the system to a more naturalized state.”
The agency noted “the alternative of doing nothing may lead to an eventual degradation of the inherent naturalness by allowing the continued decline and potential loss of a keystone species due in part to the effects of an introduced pathogen, fire exclusion policies, and climate change, all of which may owe at least some responsibility to the actions of humankind.”
If things weren’t already complicated, consider that restoration activities for whitebark pine may conflict with recovery plans for other currently endangered or threatened species whose critical habitats include whitebark pine. “In some cases, restoring whitebark pine may prove beneficial in the long-term, but the restoration actions themselves may present short-term impacts,” FWS said, noting that grizzly bears rely on whitebark pine as a critical form of sustenance in many parts of its range, “but restoration activities and the associated human presence during these may negatively impact individual bears, even if the long-term goal is improving a critical component of their habitat.”
In the case of Canada lynx, whitebark pine restoration may directly conflict with the needs of the species. “Subalpine fir is a principle component of Canada lynx habitat, yet is the primary competing species to whitebark pine that is often targeted for removal in mechanical thinning and prescribed fire treatments,” FWS noted. “Critical habitat for Canada lynx overlaps with the range of whitebark pine in many areas throughout the Northern Rockies, U.S. Canadian Rockies, Middle Rockies, and a small portion of the Cascades analysis units.”
FWS is working to develop a recovery plan for whitebark pine. The agency’s species status assessment for whitebark pine was prepared by the Wyoming Ecological Services Field Office in Cheyenne.Cat Urbigkit is an author and rancher who lives on the range in Sublette County, Wyoming. Her column, Range Writing, appears weekly in Cowboy State Daily