Tree failure following a windstorm in Brewster, Massachusetts, USA

While there are many ex post facto studies of tree failures due to catastrophic storms, relatively few have considered the effect of defects, and even fewer have explored the effect of tree maintenance, on the likelihood of failure. In light of the heightened climate of litigation in the United States, and the complexity of reliably predicting tree failure, additional studies are justified. A catastrophic windstorm in December 2005 on Cape Cod in Massachusetts, USA, provided an opportunity to study how structural defects and maintenance history affect the likelihood of tree failure. Species, height, diameter at breast height (DBH), the presence of defects, and whether trees had been pruned or nearby trees removed were recorded on trees at campsites in a park affected by the storm. The percentage of trees that failed varied among species, and evergreens failed more frequently than deciduous trees, which were leafless at the time of the storm. Large trees were more likely to fail than smaller trees, although this was not true of all species. The defects were more common on standing trees and trunk failures than root failures. Pruning trees had little effect on the failure, but removing trees increased the likelihood of root failure. The results are discussed in the context of managing tree risk.