The imminent invasion of the non-native fungus, Cronartium ribicola J.C. Fisch., that causes white pine blister rust (WPBR) and the current mountain pine beetle (Dendroctonus ponderosae Hopkins, MPB) epidemic in northern Colorado limber pine forests will severely affect the forest regeneration cycle necessary for functioning ecosystems. The slow growth and maturity of limber pine enables trees to persist on the landscape for centuries, but without sufficient regeneration opportunities these traits will inevitably hinder the ability of limber pine to adapt to novel stresses such as WPBR or climate change. The current MPB outbreak will result in the death of many mature limber pines, including many with genetic resistance to WPBR. It will be decades until advanced regeneration develops into seed-producing mature trees in much of this region. This development will be limited further by WPBR which rapidly kills susceptible young trees. Efforts to sustain limber pine and Rocky Mountain bristlecone pine in the southern Rockies were initiated in 2001.