Take photographs and make certain you mark your boundary clearly in those photos. Get an estimate for a replacement (tree + delivery + planting) and ask the neighbor to reimburse you. If they refuse you could file suit in small claims court.
The tree trimmer or his insurance company.
Get an attorney to advise you.
A neighbor cannot make you cut a tree down. BUT if your tree encroaches on a neighbor's property, causes a risk to a neighbor or their property, or causes a situation that prevents a neighbor from full enjoyment of their property, the neighbor can ask a court to make you cut back the limbs that are causing problems for their property. Your rights end where the property line begins; same for your neighbor.
um u need to talk to your neighbor and ask if he or she can allow you to cut it down
The carpenters son.
If a human cuts down a tree that was giving shade the sun can erode rocks below the tree.
a lumberjack... leaping from tree to tree in the mighty rivers of british Colombia
If your neighbor refuses to cut down the tree, use insurance or savings to cover taking down your fence (and putting up a new one), get him/her to sign a paper that says he will hand his tree over to you in exchange for a portion of money from, then put up the fence (or wall, in this case), and do with what you will to the tree. If that doesn't work, move, or trespass property by cutting down the tree, and risk getting sued.
If the tree belongs to your neighbor, it is their responsibility to maintain it. Try talking to your neighbor about the situation and see if you can resolve it together.
a lumberjack... leaping from tree to tree in the mighty rivers of british colombia
In the state of AZ can your neighbor's tree be liable for damage of your sewer?