I have seen several beavers, but usually in the backs of creeks, although a family used to live under the old ski ramp up towards Real Island. We would tie up to the ramp and catch crappie underneath it while the beavers just watched us from the low side.
There are beavers that come into to lake. My neighbors have lost several trees to beavers. All they ever take from my yard is turnip greens in the winter. Unfortunately if the bark is gone all the way around the tree it is already dead, it just doesn't know it yet. You can wrap the base with wire to try and stop them. Heavy chicken wire will do. Good luck. They are persistent.
After more thought and re-reading your post I don't think its beavers. You wrote "trees" and eating only the bark off multiple trees doesn't seem like typical beaver behavior to me. Can you peel bark off by hand where it was cut? Some beetles manifest by the bark peeling off. I learned that one the hard way.