How does a tree die? When it is cut down with an axe. But, sometimes, we may end up hurting or killing a tree without meaning to. It may happen when we carve our names or draw a heart on a tree trunk by cutting away the bark of the tree with a knife. For, along with the bark we also cut away an important tissue called phloem. This tissue carries the food made by the leaves to the other parts of the tree.
If you cut a circle around the tree by removing the bark, you end up strangling the tree. The food supply to the trunk and the roots below stops. The roots die.
When the roots die, the tree loses its supply of minerals and water that it collects from the soil. If the leaves do not get enough water, they lose the ability to make food. The tree suffers more and dies.
Sometimes, farmers cut a circle around the tree knowingly. It is called ringbarking. They do it when they have to cut down that tree later.
But it is not just humans who ringbark a tree. Even animals do it. Hungry rabbits nibble at smaller plants all the time and ringbark it. When deer rub their antlers against trees they do the same. And what about frisky cats who keep clawing plants? No wonder the best way to keep a plant alive and growing is to encircle it with a wire mesh.