These are not lichens. These are decay fungi. It means the branch contains a great deal of dead wood. The branch is either partially dead or completely dead, depending on what the top of the branch looks like. The fungi are not the problem. They are just indicators to very dead wood below them. Lichens are much smaller and more subtle. Removing the fungi will not correct the problem. Take a good look at the branch. It may need to be removed. This wood will never return to being alive.
Thank you very much for your response! Yes, the tree branches are dead however half of the tree is still living with no indication of fungi. If the dead portions are removed will the remainder of the tree remain healthy or is it a matter of time before the entire tree succumbs? I've included a few more photos, do you know what species tree we're working with here? Are there any regional trends to the overall health of this specimen?
Removing the dead branch is important. But since there are no leaves visible, I can't guess what the tree is or what happened to the branch that died. Sometimes smaller branches can be shaded by others or suffer wind or ice damage that might kill them. The two photos are the same picture, just darker and lighter.
Just remove the dead ones back to where they join a live branch. Do not cut flush with the live branch. Leave an inch or two protruding. This is the branch collar area that causes the branch stub to heal.
There is no way of guessing what's going on with the tree but the loss of an occasional branch is rarely fatal.