Climate change and the associated changing weather patterns occurring worldwide have a direct effect on biology, population ecology, and the population of eruptive insects, such as the mountain pine beetle (MPB). This is because temperature is a factor which determines insect development and population success. Mountain Pine Beetle are a species native to Western North America. Prior to climatic and temperature changes, the mountain pine beetle predominately lived and attacked lodgepole and ponderosa pine trees at lower elevations, as the higher elevation Rocky Mountains and Cascades were too cold for their survival. Under normal seasonal freezing weather conditions in the lower elevations, the forest ecosystems that pine beetles inhabit are kept in a balance by factors such as tree defense mechanisms, beetle defense mechanisms, and freezing temperatures. It is a simple relationship between a host (the forest), an agent (the beetle) and the environment (the weather & temperature). However, as climate change causes mountain areas to become warmer and drier, pine beetles have more power to infest and destroy the forest ecosystems, such as the whitebark pine forests of the Rockies. This is a forest so important to forest ecosystems that it is called the rooftop of the rockies. Climate change has led to a threatening pine beetle pandemic, causing them to spread far beyond their native habitat. This leads to ecosystem changes, forest fires, floods and hazards to human health.