Weak crotches should be removed, or if cabled, inspected frequently. Decay Structural weakness due to decay, target cankers, or splits must be inspected closely. When in doubt as to the tree's soundness, remove the hazard. Construction damages Site conditions and alterations to the site due to construction create some of the most dangerous trees in the human-controlled tree environment. Root cuts, high water tables or ledges all increase the likelihood of wind throw.
Wind throw is most likely when surrounding trees have been removed, as on a new play ground.
Root problems Root rots, girdling roots and backfilled trees can all create hazardous situations. Each of these problems exhibits its own symptoms and park inspectors should be familiar with each. Lightning Trees struck by lightning can be extremely dangerous. Each year thousands of trees are hit, but many could be protected with professionally installed lightning protection systems. Eleven percent of house fires are caused by lightning striking trees.