Tree Damage Series: Engulfing Forgotten Chains and Inconvenient Barriers
This Honey Locust (Gleditsia triacanthos) with an old lock and chain that had been left around its trunk.
This tree has already been given its death sentence. The chain left around its trunk is being engulfed by the tree, but upon being embedded into the bark it will eventually cut off the flow of water and nutrients above the chain.
Though the subject of many a tree meme, the item, whether a chain or a fence, is not "being eaten" by the tree, but rather the tree is continuing to grow while overcoming the obstacle in a way the may ultimately injure or kill it. The repeated rubbing against a fence or pole will continuously injure the tree's bark, opening up wounds for pathogens to enter. When the tree grows around an item that is along its trunk's perimeter. it will effectively strangle itself, and starve to death over time. This process is known as girdling.
Courtesy of Instagram
You may see trees engulfing fences and poles and seem to be doing fine. This could indeed be the case, because if only part of the trunk is girdled, then the tree should be able to survive. However, this weakens the integrity of the trunk and increases the chances of it toppling over during a strong storm or if weighed down by ice and snow.
A type of girdling is also commonly used as a way of passively killing invasive trees, referred to as ring-barking, which is achieved by stripping the bark around their circumference and causing their eventual death. There have been cases of illegal ring-barking in several nature preserves and state parks around the country, most notably a case of a "serial tree killer(s)" in Michigan that killed over 30 cherries and .
Courtesy of City of Burnsville
The motive may have been to return and poach (harvest) the wood, and many theorize it would be a contractor that wishes to be hired to remove the trees after they perish, so that they in turn could use the wood in carpentry and make a profit.
If you notice a badly girdled tree, especially if it has died and could potentially be in danger of falling over, please call 311 and have them connect you to the proper channels to have it safely removed.