Insects, diseases and severe weather events damaged about 40 million ha of forests in 2015, mainly in the temperate and boreal domains.
[3] There are a number of abiotic factors which affect the health of a forest, such as moisture issues like drought, winter-drying, waterlogging resulting from over-abundance or lack of precipitation such as hail, snow, rain.
For example, if wind speed is 80 km per hour then many trees which have root rot (caused by a pathogen) are likely to be thrown.
Additionally, poorly planned but conventionally replanted (post-cut) forest plantations are typically monocropped, and highly susceptible to further insect or fungal infection due to low biodiversity and diminished capacity for community resilience - see the "Wood wide web".
Forest entomology also includes the management of insect pests that cause the degrading, defoliation, crown die-back or death of trees.
Thus the scope is wide and includes: The likelihood of property damage or personal injury due to tree failure.
Rating systems, procedures and guidelines have been developed for decision making but knowledge, judgement, and experience are an important part to the process.