Navmesh surface causes performance issues for unity.

Hi,

I am new to unity and I have a large terrain piece 32000 by 32000 for my entire game. When I added a Navmesh surface so that I could put enemies in my game it caused unity to become really slow.

I am running on a pretty good Mac but any edits I make or even just opening up the project causes the loading wheel to spin for about a minute or two. It wasn’t like this before I baked the Navmesh.

Also, it took about an hour to fully bake but from what I have heard this is understandable. My suspicion is, that the large terrain piece is causing it to act like this but I don’t believe there is any way to split up the already made terrain. Is there any way I can make it faster?

Thanks,