> On the other hand, if the entity owns itself, you can’t legally harm it without consent, which can’t be given.

By the same token, the forest can't exactly start a lawsuit either (unless someone acts on its behalf, in which case we are back at the same person).

Just because they declared it a legal person, doesn't mean it actually is, in terms of how that phrase is normally used. At the very least a legal person normally can enter into contracts, buy and dispose of property. Like you said, the forest can't consent, and being able to consent is what it means to be a person.