an arborist who has passed an independent exam administered by the International Society of Arboriculture. and maintains the credential through continuing education.
Certified Arborist (Wikipedia)
The Certified Arborist credential identifies professional arborists who have a minimum of three years' full-time experience working in the professional tree care industry and who have passed an examination covering facets of arboriculture. The Western Chapter of the International Society of Arboriculture (ISA) started the certification program in the 1980s,[citation needed] with the ISA initiating it in 1992.
