The temperate_dead_forest.xml actor is being removed because it remains visible even if someone builds a structure on top of it.
@wow was okay with them to be deleted from the maps.
IRC 0ad-dev (27/Jan/22)
[18:31:44] Langbart_ Dr. wowgetoffmang can I remove the actor file from the belgian_bog map? #6425 [18:32:56] wowgetoffmang They were placed there as a test, honestly. [18:33:02] wowgetoffmang So, you can remove them. [18:33:41] wowgetoffmang The full-featured solution is that some actors should have a flag that allows them to be removed if something is built on top of them. [18:34:01] wowgetoffmang Various grass actors, for instance. [18:34:41] wowgetoffmang Most modern games have something like that I've seen.