Limber Pine Conservation

Limber pine tree.

NPS photo

Limber pines (Pinus flexilis) are five-needle pines that inhabit Rocky Mountain National Park (RMNP). Limber pines are a keystone species that provide important ecosystem services like facilitating forest establishment and succession, providing food sources for wildlife, and aiding in soil stability and snow retention. Within RMNP, limber pines are designated as a Species of Management Concern because of their importance in maintaining biodiversity in the park.

Limber pine populations in RMNP and the surrounding area are declining due to climate-exacerbated drought and mountain pine beetle outbreaks. Since 2010, limber pines in the park have faced the additional threat of white pine blister rust (WPBR) - a fatal disease caused by a nonnative fungus. Scientists predicted that the combined effects of these stressors would result in a 40% loss of limber pine by 2030 without intervention

White pine blister rust on limber pine branch.

NPS photo

In response to these declines, many efforts have been taken to proactively manage and protect limber pines in the RMNP region. Park managers work collaboratively with partners at the U.S. Forest Service to implement the Proactive Limber Pine Conservation Strategy. This multi-pronged strategy allows managers to monitor limber pine populations, apply bark beetle deterrents to limber pines in the form of verbenone packets, strategically prune limber pine branches with signs of WPBR (most easily identified by orange/rust-colored cankers that grow on the bark), collect limber pine seeds for seed banking, and plant limber pine seedlings to restore affected limber pine populations. The Conservation Strategy also promotes scientific research on limber pine genetics that can be used to further support conservation efforts. One study found Rocky Mountain National Park and the surrounding area has an unusually high percentage of limber pines that carry a WPBR-resistant gene – the “Cr4” gene.

Rocky Mountain National Park has a Forest Health Program with dedicated staff who help implement the Proactive Limber Pine Conservation Strategy. Park staff collect data on limber pine health and apply verbenone packets annually in 17 plots throughout the park. In September of 2023, park staff also planted 270 limber pine seedlings near Mirror Lake in the northern part of the park to restore a limber pine stand lost to the 2020 Cameron Peak Fire.

Forest Health ranger applying verbenone pouch on limber pine to deter mountain pine beetles.

NPS photo