Saving Limber Pines in Rocky Mountain National Park

A limber pine. Photo: NPS.

Limber pines (Pinus flexilis) are five-needle pines of Rocky Mountain National Park. They are a keystone species: they help forests establish and succeed one another, provide food for wildlife, and help stabilize soil and hold snow. Because they matter so much to the park's biodiversity, the park lists them as a Species of Management Concern.

Why they are declining

• Drought, made worse by climate change, and mountain pine beetle outbreaks are reducing limber pines in and around the park.
• Since 2010 they have also faced white pine blister rust (WPBR), a fatal disease caused by a nonnative fungus.
• Scientists predicted that, without intervention, these stresses together would kill 40% of the park's limber pines by 2030.

White pine blister rust on a limber pine branch. Photo: NPS.

Fighting back

Park managers work with the U.S. Forest Service on the Proactive Limber Pine Conservation Strategy, which lets them:

• monitor limber pine populations;
• deter bark beetles with verbenone packets attached to the trees;
• prune branches showing blister rust — most easily spotted as orange, rust-colored cankers on the bark;
• collect seeds for seed banking;
• plant seedlings to restore stands the threats have hit.

The strategy also backs research on limber pine genetics. One study found that the park and its surroundings have an unusually high share of limber pines carrying a gene for blister rust resistance, the "Cr4" gene.

The park's forest health program

The park's Forest Health Program has dedicated staff who carry out the strategy. Each year they collect data on limber pine health and apply verbenone packets in 17 plots across the park. In September 2023, staff planted 270 limber pine seedlings near Mirror Lake, in the park's north, to restore a stand lost in the 2020 Cameron Peak Fire.

A forest health ranger attaches a verbenone pouch to a limber pine to deter mountain pine beetles. Photo: NPS.

Sources

Based on "Limber Pine Conservation," Rocky Mountain National Park, National Park Service; a work of the United States government in the public domain.