“A variety of forces and influences has shaped forest ecosystems throughout the evolutionary history of trees and forests. Native insects and pathogens, extreme weather events, and cyclic fires are part of normal ecosystem structure and function that includes weakening, death, regeneration, recycling, and replacement of trees and forests. Forests are adapted to endemic levels of native insects and pathogens that periodically become epidemic and temporally cause greater effects that recede with time. Periodic extremes of weather or long-term shifts in climate are also natural occurrences and forests adapt in a variety of ways. Fire is also an essential component of forest ecosystems, and provides many beneficial effects when it occurs within normal cycles of frequency and severity….Exotic pathogens have greatly altered the composition, structure, and function of some forests.”
http://www.thefemaleangle.com/ provided the impetus for a little research.
SwittersB & Exploring 