Too many Tamarisk Trees. The AI doesn't know that villagers cannot gather wood from this tree so they try. They chop and chop until the tree is destroyed(hit points to 0) without getting a single log. Then they will go to another one and try again. I guess they figure the 20000 wood it is supposed to have is better than the 150 of a normal tree. Seems like a bug, either the AI shouldn't try or they should get wood for their efforts.