The risk mapping effort was initiated in 1995 with the formation of a group of specialists from several disciplines including representatives from state and other federal agencies to map and identify risk to insect caused tree mortality. An area is defined to be at risk if 25% or more tree mortality (beyond the normal level of approximately 0.6% annually) is expected over the next 15 years. This effort developed a statewide insect mortality risk layer based upon rules and statistics developed for the National forests and expanded to cover all state and private forest land. Rule structures were based primarily upon stand density index and also included, precipitation, percent canopy cover of host species, and host type.
