Since the early days of Mortal Kombat, the series has had a wonderfully B-movie-like approach to universe building. Gods, portals to other realms, skeletal ninjas returning from the dead, shapeshifters, cyborgs, monsters, and things you figured would never really be explained because they were just there for the hell of it.
Why were there screaming trees in the background of Mortal Kombat 2? I never felt the need to know as a kid; just looking cool was enough.
Turns out the trees—excuse me, the Living Forest—has a fan wiki entry and a multi-game-appearance track record, because of course it does. The Mortal Kombat team has developed a fanatical devotion to building out their game world over the decades. Their dedication is matched only by the enthusiasm of the franchise’s fan base to consume and dig into this backstory.
Source: Ars Technica – Unsolved Mysteries of the Mortal Kombat Universe