To deter cats from climbing and damaging your Christmas tree, there are several methods you can try. First, try using a deterrent spray or cat repellent around the base of the tree. This will create an unpleasant smell that cats will want to avoid. Another option is to place double-sided tape on the trunk and branches of the tree, which will make it uncomfortable for the cat to climb. You can also try placing a few prickly objects around the base of the tree, like pine cones or pieces of cardboard, to deter the cat from approaching.