Is it dead or alive? Is there anything I can do to treat it or do I need to cut it down and re-plant?
Certified GKH Gardening Expert
I'm not sure what I'm looking at here, but there's a scratch test you can do that will help you determine whether the tree has died. It's described here: https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-scratch-test.htm
I suggest you consult with an arborist if you aren't sure; it would be a shame to remove the tree if something could be done to save it. This article on magnolia diseases may help: