The credential
What an ISA Certified Arborist Is
An ISA Certified Arborist has passed the International Society of Arboriculture's written exam in tree biology, diagnosis and risk.
That testing is what separates an arborist from a general tree trimmer: the training is in why a tree is failing, not only in how to cut it. The Georgia Forestry Commission advises having tree care done by a certified arborist trained in tree diagnosis, and TreesAreGood.org: Why Hire an Arborist lays out what the credential covers and when removal is warranted.
When the answer is pruning rather than removal, our trimming page covers how that work goes.
tree trimming in Alpharetta