CLIMATE CHANGE & VARIABILITY
There are substantial concerns that greenhouse gas induced climate changes will impact high elevation areas. Conflicting predictions obscure certainty on what may occur under future climate conditions. However, in all cases, elevational shifts in vegetative composition are expected. Many scenarios forecast a loss of native high elevation subalpine forests; as other species disperse up the mountains, the current high elevation species will eventually get squeezed off the mountain tops.
The rate of these types of changes would more than likely be slow and subtle, given the longevity of the high elevation pines. The mature trees are less sensitive to environmental conditions than their seedlings. Future climatic conditions may prevent the survival of seedlings of high elevation species where they once were abundant.
Warming temperatures may result in increased mountain pine beetle activity. Mountain pine beetles that were once restricted to lower elevations because of low temperatures at high elevation may move into higher elevation areas. As temperature increases the probability of outbreaks at high elevation may increase.
This was demonstrated in the 1930s in Idaho, when a decade long warming period (temperatures were more than 4.5 degrees F above average) caused significant mortality by Mountain Pine Beetle in Whitebark pine at elevations up to 10,000 ft. Today, Mountain Pine Beetle is aggressively attacking whitebark pine which grow at elevations of 5,000 to 10,000 ft in the western US and British Colombia. Other climate driven variable such as drought and fire can stress trees and make them more vulnerable to insect attacks.
Referred Literature: 89, 121