I don't get it. Are you saying it's skinny or weak? There is no way on this planet someone could break through that. Just the last long is 2 inches in diameter but it doesn't really matter. The one at the end is the skiniest unusally and even so it has no flex. The rest are between 3-4-5 inches thick. Try break through those fat bastard.
Cedar is rot resistant. It will take years for any damage to become apparent. Wherever the wood is in contact with the ground is a potential problem area, but the wood is so thick and heavy that it will last many years. The wood up top will last even longer.
http://www.pinkbike.com/photo/2190935/
Lets have a look at the thickness..