Trees provide a variety of benefits to society. But trees also lose branches or break when forces exceed their structural strength or the root-soil connection. Tree failure can cause severe damage to houses and other structures, deny access or use of infrastructure, and injure or kill people. Landowners have legal “duty of care” for trees on their properties, including responsibility to obtain expert assistance when appropriate. Learn how qualified arborists assess tree risk by estimating likelihood of tree failure and impact, and the consequences to property and people. Dr. Glen Stanosz is the UW-Madison emeritus professor of tree and forest health, and is also a certified arborist with the additional qualification in tree risk assessment.