A harsh environment is really needed for Unturned A air that carries disease is a good example and that air occurs randomly in random places that carried disease and could decrease your Green Bar thingy and makes you slow and give you damage per second if your in the way of the Polluted air the air moves in the whole map for like 10 Minutes or something
Another Examples
An earthquake that could deal huge amount of damage of your base
Some UV rays that raises your body temperature depleting your water bar and forcing you to get in a nearby shelter and give you sunburn and damages you
An acid rain that could damage your base and you if your outside
I think besides making survival more difficult, events like these would encourage survival gameplay by discouraging sedentarianism. Although I don’t particularly like any of the examples, I do agree with the general idea of the post.