Certified GKH Gardening Expert
What kind of trees are these? How old are they? And do you know what caused their decline? This information will help us to give you accurate information about the care for these trees.
As for whether or not the trees are actually dead, you can check this yourself by gently scrape the bark to see if there is any green underneath, and if so, it is still alive. If it's brittle and brown, then it's dead. Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/trees/tgen/what-does-a-dying-tree-look-like-signs-that-a-tree-is-dying.htm