An arborist (or tree surgeon ) is a professional who manages and maintains trees (generally in an urban environment). This can include planting, pruning, structural support, the treatment of disease, insect, or abiotic disorders, lightning protection, and tree removal. It also can include planning, consulting, report writing and even legal testimony. Because trees provide many benefits to the landscape and to people, but they are also very large, heavy, and complex organisms , they require monitoring and care to ensure survival and safety in the human landscape
Trees may require pruning to keep them away from wires, fences and buildings, to improve long-term health and/or structure, for aesthetic reasons, and to permit people to walk and sit under them. They might also require other care to improve their chances of survival and longevity, or treatments in response to damage from biotic or abiotic factors. Trees in urban landscape settings are often subject to human disturbances, as well as natural disturbances. Timing or methods depend on the species of tree and the purpose of the work. A thorough knowledge of local species and environments is necessary to determine the best practices.
Pruning should only be done with a specific purpose in mind. Every cut is a wound, and every leaf lost removes some amount of photosynthetic ability. Proper pruning can be very helpful in many ways, but should always be done with the minimum amount of live tissue removed for the individual situation.