How Arborists Work

Arborists are experts in proper tree care, providing many services that include planting, maintaining, saving and removing trees.
Arborists are tree care experts, providing many services that include planting, maintaining, saving and removing trees.
Lester Lefkowitz/Getty Images

­Whether you're in small town with forests that spread for miles or a large, developed city with arboreal parks, it's easy to see that people have strong connections with the trees in their areas. They provide us with shade from the hot sun during the summer months when their leaves are full, and trees planted next to a home can reduce air conditioning costs by as much as 15 percent [source: International Society of Arboriculture]. During the winter months, when trees lose their leaves, they let sunlight in to warm our homes. Depending on the type of trees you select to plant around your home, they may even be able to act as wind obstructions, blocking cold, blustery weather.

Large groups of tree in cities­ can reduce what's called the "heat-island effect," the significant warming that comes from replacing large areas of natural land and vegetation with buildings, roads and asphalt. The temperature around a shade tree is significantly cooler than the temperature around a parked car, and several trees planted over a stretch of sidewalk can give shade and reduce reflected heat.


Our breathing processes are also mutually beneficial -- while we breathe in oxygen and expel carbon dioxide, trees take in carbon dioxide and produce oxygen. Their leaves can also filter out pollutants from the air.

­Trees can also make your real estate more attractive and possibly increase the price of your home if you're ­looking to sell. Which brings us to the most basic aspect of our relationship: Trees are a pleasant sight to take in, and we simply enjoy admiring them for their beauty.

Keeping trees healthy is difficult, however, and not everyone has the skills to take care of them properly. Doing so usually involves dangerous climbing and hazardous situations. That's why it takes an arborist, a certified specialist in taking care of trees, to look after trees. Read on to learn about what an arborist does.


Arborist Services

An arborist's job can range from routine -- sprucing up tree branches -- to dangerous -- removing tree branches from power lines. Here, arborist John Massing sprays pesticide at the base of a horse chestnut tree in Central Park, New York City.
Arborist John Massing sprays pesticide at the base of a horse chestnut tree in Central Park in New York City.
Melanie Stetson Freeman/The Christian Science Monitor/Getty Images

­Arborists are well-versed in arboriculture, the study of trees and how they grow, and they spend years receiving specialized training to secure their positions as proper custodians of trees.

Because the health of the trees around us is important to the entire environment, and not just humankind, arborists must know every angle there is to tree care. Taking care of trees is a very specialized practice, and it not only requires a great deal of knowledge but a lot of skill and experience. Much of tree care involves climbing high into the branches, which can be very dangerous and requires serious training.


One of the main services an arborist provides for cities, states and other organizations is pruning. Although branches are­ certainly important to a tree, there are times when it's necessary to remove branches to promote proper health and growth. Branches that rub against each other, for instance, damage a tree's bark, so arborists can and will remove them if they grow too close together. An arborist can also remove branches that are weak, diseased, insect-infested or in the process of dying, since one dead branch can cause the entire tree to decay. Any limbs that create a hazard or obstruction for people, including drivers, should also be cut for safety's sake.

Entire trees sometimes have to be removed by arborists, too, although it's a last resort. An arborist will only remove a tree if it's dying or dead, if it causes an obstruction or hazard that can't be fixed by pruning or if it rests in a spot that will undergo construction. If a business wants to remove a certain number of trees to develop buildings and other infrastructure, an arborist can approve or deny any plans and provide consulting on future plans for tree planting around the development. If businesses illegally remove trees without permission, arborists have the ability to issue citations with big fines -- movie director and actor Tyler Perry, for instance, was fined $177,000 for illegal deforestation around his Atlanta home in 2008 [source: Brown].

Storms can cause lots of damage to trees, and after a storm it's an arborist's job to safely clean up the mess. They clear away any branches or limbs that fall onto the road or on top of houses, cars and power lines. They also remove any trees irreversibly damaged by the storm.

Finally, many arborists are typically eager to promote tree planting and tree growth, and have extensive knowledge about how and where to plant trees. Location is especially important in tree planting. Knowing the specific climates and regions in which a tree can thrive and being aware of the various diseases and insects a tree can fall prey to will ultimately affect the success of that tree.

How does an arborist actually become an arborist? Find out on the next page.


Arborist Certification

The International Society of Arborists certifies professional arborists in several levels of professional skills.
The International Society of Arborists certifies professional arborists in several levels of professional skills.
Reza Estakhrian/­Getty Images

­If you thought taking care of trees was a simple, straightforward job, think again. Anyone who wants to become an arborist must spend a great deal of time studying, preparing and getting experience in the world of trees, and becoming a licensed professional can take years of hard work. Arborists will typically study at any number of two- or four-year college programs, getting a degree in arboriculture, horticulture or a combination of the two studies.

After joining any number of arborist associations, including the Tree Care Industry of America (TCIA) and the American Society of Consulting Arborists (ASCA), the main goal is to get certification from the International Society of Arboriculture (ISA). There are essentially five different licenses an arborist can acquire from the ISA along his or her career path. Before receiving each one, arborists must take an exam that tests their knowledge, abilities and experience. The largest group of licensed arborists is the Certified Arborist, the first certification an arborist can receive. These credential holders generally have basic knowledge of tree science and basic skill in tree care. ISA Certified Arborists must have at least three years of experience before they take the exam, which covers all areas of arboriculture.


Within this group, however, arborists can take another test to receive a second, more specialized certification: the Certified Tree Worker, which designates the arborist as a climber specialist. An arborist who wants to become a Certified Tree Worker needs to have at least 18 months of professional tree climbing and should have the necessary skills, including pruning, tree removal, cabling and safety. The exam is both written and skill-based, the latter of which is conducted by skilled evaluators.

Above the Certified Arborist are two positions: the Utility Specialist and the Municipal Specialist. Utility Specialists have the specific job of caring for trees around power lines. Any time there's a fallen tree near dangerous electrical equipment, a Utility Specialist must be able to safely remove any potentially hazardous branches from the scene. A Municipal Specialist, on the other hand, works more broadly in urban areas, working in city and state parks often alongside contractors and consultants.

The highest certification an arborist can achieve is ISA Board-certified Master Arborist, meant for experts in the field of arboriculture with years of professionalism in tree care. The Board-certified Master Arborist must meet a list of specific prerequisites that cover experience and education and also complete a 150 question exam developed by industry experts. The number of Board-certified Master Arborists around the world should tell you how challenging the certification is -- there are only 120 Board-certified Master Arborists internationally [source: Autumn Tree Care Experts].

For lots more information on trees and tree care, see the links on the next page.


Lots More Information

Related HowStuffWorks Articles
More Great Links

  • Brown, Robbie. "Atlanta tree lovers see victory for developers in arborist's firing." The New York Times. Aug. 5, 2008. (Dec. 1, 2008)
  • DeGeeter, Jayson. "Arborists receive ISA's highest honors." Autumn Tree Care Experts. April 21, 2006. (Dec. 1, 2008)
  • International Society of Arboriculture. "ISA Board-Certified Master Arborist." (Dec. 1, 2008)
  • International Society of Arboriculture. "ISA Certified Arborist." (Dec. 1, 2008)
  • International Society of Arboriculture. "ISA Certified Arborist/Municipal Specialist." (Dec. 1, 2008)
  • International Society of Arboriculture. "ISA Certified Arborist/Utility Specialist." (Dec. 1, 2008)
  • International Society of Arboriculture. "ISA Certified Tree Worker/Climber Specialist." (Dec. 1, 2008)
  • International Society of Arboriculture. "The ISA Certification Credentials: the Right Certification for the Right Job." (Dec. 1, 2008)
  • Trees Are Good. "Benefits of Trees." (Dec. 1, 2008)
  • Trees Are Good. "Why Hire an Arborist." July 2005. (Dec. 1, 2008)
  • United States Environmental Protection Agency. "What is an urban heat island?" Oct. 16, 2008. (Dec. 1, 2008)