The arborist concerns themselves with the continuance of the tree civilization. Trees are valuable. They are very generous in the gifts they give mankind. Trees give us oxygen we breathe, filter the air of pollutants, provide shade, wood, fruits and nuts, absorb sound, provide visual pleasantries, and a place for humans to play under or in. Trees can also become problems as they try to coexist with human beings of this planet.
Trees grow old and get sick.
They eventually die. They can topple and kill people or drop branches unpredictably. It's important to keep trees around. It's equally important to be aware of a tree's problems so they can be properly cared for and replaced when it is necessary. This falls into the expertise of a certified arborist.