It typically grows in dense, even-aged stands that have regenerated following intense wildfires that killed the previous stand. Life Cycle of the Mountain Pine Beetle

The mountain pine beetle is a seasonally adapted insect, successfully reproducing and occasionally reaching epidemic levels where it is univoltine —completing an entire life cycle in one year. The mountain pine beetle, in turn, has evolved a mass-attack strategy that overwhelms tree defenses through sheer numbers of attacking beetles." Thus, trees under stress—from drought, disease, injury, or other cause—are more susceptible to attack by the mountain pine beetle and blue-stain fungus. When a widespread stress (e.g., a regional drought) affects a forest with many relatively large-diameter lodgepole pine trees, the stage is set for a mountain pine beetle epidemic. Most researchers note that mountain pine beetle epidemics are known to have occurred in lodgepole pine forests, but that the current epidemic is more extensive than has been seen in the past century. The epidemic may have been exacerbated by climate change. The Lodgepole Pine Epidemic in Canada

The interior forests of British Columbia (BC), stretching west from the Rocky Mountain crest to the east side of the Coast Range, are similar to U.S. forests of the Rocky Mountains, and include extensive stretches of mature lodgepole pine. As with the lodgepole pine forests of the central U.S. Rockies, the mountain pine beetle is an endemic (native) species, with periodic epidemics. This is likely the result of climate change leading to insufficient freezing temperatures farther north than previously recorded. As with the mountain pine beetle outbreak in extreme northern BC, climate change is likely a significant factor in the current epidemic in high-elevation pine ecosystems, because warmer temperatures allow the mountain pine beetle to become univoltine in these areas. As one group of researchers noted, "once MPB [the mountain pine beetle] infests a tree nothing practical can be done to save that tree." Individually valuable trees, such as those near residences or in campgrounds, can be protected by insecticide sprays, but the cost is prohibitive at a landscape scale. Silvicultural treatments (timber harvests and other tree stand management practices) are sometimes discussed as a way to restrict the spread of the mountain pine beetle, but some observers have noted that such efforts are unlikely to make a difference, at least in the short run: 
In the current epidemic, it is impractical to expect that silvicultural treatment of lodgepole pine forests will prevent or even impede the advance of the epidemic in Colorado and southern Wyoming. Ecological Consequences

The mountain pine beetle epidemic has two primary impacts of concern: first, the possible increase in wildfire threat, and second, forest regeneration following the epidemic. The effects on the high-elevation pines are different, and are discussed separately. Ecological Effects on Lodgepole Pine Ecosystems

The initial concern about the ecological impacts of mountain pine beetles on lodgepole pines is the apparent increase in the threat of wildfire conflagrations from the large numbers of dead and dying trees. Lodgepole pine forests historically burned occasionally, typically in crown fires (conflagrations that kill most of the trees in the stand) under extreme weather conditions. In addition, the high-elevation pines are susceptible to destruction by white pine blister rust. However, lumber markets could be a problem. The largest market for Canadian lumber is the U.S. housing market. There are some limitations to the potential use of beetle-killed timber for energy production. Capacity could be built, and the wood might still be available for many years, but some of the capacity to use the substantial volume would become superfluous after the available beetle-killed timber was all used.
The mountain pine beetle is a native insect of western U.S. pine forests. It survives by killing infested trees, usually individually, but occasionally in epidemics. Mountain pine beetle epidemics are particularly associated with lodgepole pine, a common western tree that typically grows in dense, even-aged stands. The beetle is a seasonally adapted species that thrives in areas where it can complete its life cycle in one year. The beetle has evolved a mass-attack approach to overwhelm tree defenses through large numbers, and adults congregate on large trees under stress. Widespread stress (e.g., a regional drought) sets the stage for an epidemic.
Mountain pine beetle epidemics are recurrent events in western forests. The current epidemic can be separated into three distinct events: the central U.S. Rocky Mountains, interior British Columbia (Canada), and high-elevation pines. Two aspects of the current epidemic are widely believed to have been exacerbated by climate change: (1) increased temperatures farther north and at higher elevations (allowing complete life cycles in areas previously not susceptible to the beetle) and (2) possibly regional drought (making trees more susceptible to beetle attacks).
Controlling a mountain pine beetle epidemic can be problematic. Individual trees can be protected by insecticide sprays, but the cost of preventive spraying at a landscape scale is prohibitive. Once a tree is infested, nothing can be done to save the tree. In the long run, silvicultural treatments to provide less dense, more diverse forests may reduce the extent of future epidemics, but epidemics cannot be prevented.
One concern about the consequences of the current epidemic is the possible increase in wildfire threats. Little research has been done to assess the change in threats and impacts of wildfires. The limited existing information suggests that tree mortality due to mountain pine beetles may have little effect on the threat or impacts of wildfire in the affected areas, because lodgepole pines (live or dead) naturally burn in extensive crown fires that typically kill most of the large trees. Furthermore, because of the natural regeneration cycle of lodgepole pine and because the beetles do not kill small trees, natural regeneration of the pine forests is likely.
However, warming as a result of climate change could have two consequential ecological outcomes. First, the beetle outbreak in the high-elevation pine ecosystems could significantly alter these ecosystems, because these pines are much slower to regenerate and small high-elevation pines are highly susceptible to the white pine blister rust (an introduced fungus). The second concern is the potential for the mountain pine beetle to spread across northern Canada through the boreal jack pine forest, and become an invasive pest of eastern pine forests.
There are economic consequences of the mountain pine beetle epidemic. The aesthetic values of the area—such as property values and tourism—will likely be harmed by the extensive tree mortality. Much of the beetle-killed timber could be used, for lumber or for biomass energy, but the substantial volume of timber available far exceeds existing capacity to use the wood, and expanding capacity could be unsustainable—a short-run surplus and long-run shortage. Also, Canadian lumber faces restrictions on shipments to U.S. markets.