Bark girdling is a real issue, and it can kill a landscape tree. This type of girdling occurs when too much bark is lost around the circumference of the tree. When this occurs, the inner layer of bark is no longer there to aid in the transport of nutrients to the branches above, which will eventually cause the tree to die. Fortunately, you can prevent this from happening if you know the main causes and how to prevent them.
In the average yard, mechanical damage is likely the main culprit. Hitting the tree bark with a weed trimmer or ramming a lawnmower against it can eventually cause bark to crumble and fall off. Mechanical damage is completely avoidable. The simplest option is to change your landscaping. Install a buffer zone around the base of each tree by removing sod and installing mulch. This way, you never need to mow or trim weeds adjacent to a tree trunk. Just make sure the mulch isn't piled too high, or it can trap moisture and cause the bark to rot.
Domestic animals don't generally cause major damage to tree bark, but wild animals can. Animals like deer, squirrels, and porcupine will peel off the bark to eat. In time, too much bark is lost and the tree dies. Exclusion can help protect your tree if it is exposed to this sort of damage. Tree guards are made of plastic. They slip around the trunk of a tree so that no animal can reach the bark. They are designed to expand as the tree grows. You can also create your own guard from chicken wire. Form it into a tube around the trunk, making sure it is a few inches larger than the trunk's diameter, but not so large that smaller pests like squirrels can get down the tube and to the bark. This homemade version won't expand, so you will need to replace it with larger wire tubes as your tree grows.
A tree can be a handy place to rig up a clothesline or hang a hammock. Unfortunately, ropes left around the trunk too long can also cause girdling. Combine this with bark loss from rope friction, and you have a real problem. Placing a wide strip of cloth around the tree before tying a rope in place cuts down on friction damage to bark. Then, make sure ropes are removed promptly after use and never leave one in place for more than one season.
For more help, talk to a tree service professional like those at S.A. Total Tree Service.