Survival - Desert

[Jeminai]

I am going to be starting a Dark Sun game pretty soon and in that setting (mostly desert) there are many types of desert landscapes (just like on earth).

How should I handle suvival rolls on different types of desert landscapes?

Darksun has some of the following desert types among others. These landscapes are very different and IMO should require different penalty types off of Survival (Desert).

Scrub Plains: typical mojave or australian outback landscapes with ample vegetation including desert hardy shrubs and cacti.

Sandy Wastes: typical sahara or Namib desert landscape. sandy dunes with almost no vegetation for as far as the eye can see and much farther.

Rocky Badlands: typical Utah canyon lands with mazes of canyons. Plenty of shade in anytime of the day that is not high noon or the couple of hours around that time. vegetation can be readily found in canyon bottoms where water is most likely to collect.

Salt Flats: typical Uyini Salt Flat or Bonneville Salt flat. Large expanses of of flat open salt crusted land. Any standing water is fouled by the salt, plants are exceedingly rare.

In typical games a Salt Falt is a desert and would default off of Survival (Jungle) at -3. I just don't think this fits. A Salt flat is much harder to survive on that the Utah Canyon lands (which has more water, plants and animals).

If i am misunderstanding how Survival works, please enlighten me. Survival is an important part of the game experience in Dark Sun.