In the real world nature can be brutal, with tornadoes, volcanoes earthquakes, and even tsunamis, wich all have alot of destructive power and the ability to change the face of the earth (some more than others). this should also affect the world in dwarf fortress, things like tornadoes and thunderstorms would affect areas on a per fotress/town basis, while earhtquakes volcanoes and tsunamis affect the world. these would be rare, as no one wants a new section of chasm dug into their fortress. but others like volcanoes would be a double edged sword, YES the elephants ran away scared as they bashed through your front gate, but the ASHES have killed most of the outdoor plants and killed most of the fish in the river. YES the hurricane has torn the outside up and flooded it, But the nearby goblin outpost took heavy casualties. things like hurricanes and tsunamis would affect coastal cities, while earthquakes and volcanoes affect the inland. other things include that fortress you were going to build, last you looked it was calm and had lots of trees and underbrush, but after that volcanoe erupted miles away, the plants are mostly dead and the animals mostly gone. All of these may happen once or twice during your time on the world (maybea not at all if your lucky) while thuinderstorms and tornadoes would happen every once in a while while at your fort.