I also believe that the skills learnt in one climate will not, necessarily, translate into a different one. If you took an Eskimo from Alaska with incredible foraging and survival skills, how long would they last in the Australian outback with 50c temperatures and no water? Would the skills learnt from Alaska help in this environment?
Hehe... I'm having the same arguement with my flatmate. I agree with you in this area of disparity. Although an extreme arguement. If the Inuit was to slowly traverse, they would adapt their skills slowly. If they were dumped in the desert, it would depend on whether they knew what was going on or not. If they didn't know what was happening, then it would depend on their innate survival skills and adaptablility. If they were the beast in their own environment but unable to adapt easily, then they will die quickly.
My arguement is this... If a character chooses to speicalise in Foraging/Survival: Arctic at first level, they will be able to use this skill in tundra, steppes, areas of permafrost and ice caps and other infertile lowlands in cold climates. This person will know how to
safely gather water which is applicable in all environments (unless you're a dwarf in which case you just brew beer), gather food (stalking prey, tracking, knowing what is/isn't safe to eat e.g. bear cubs when mama bear isn't around) and the provision of shelter (creating an area where you are protected from the elements). The fact that the character is not conditioned/trained for an environment is where the -25 penalty comes from. I suppose it could be raised to -50 or maybe have all difficulties raised by three. Anyway... the principles of the providing the three necessities to human(oid) survival should all be the same.
If Bob (from my previous example) took Foraging/Survival: Waste (covers deserts) and Arctic (he's half Aborigine and Inuit), he'll know that to look for water in the Arctic you have to find a stream or safely melt and boil the water. In the desert, he would know to look for areas of vegetation for cactus type plants, oases or waddis (middle east). The point is, if water isn't on the surface, it's either in the sky or underground. Certain areas will have a predisposition to where it is located.
In regards to shelter, one would know that being too hot or too cold is dangerous. Therefore you seek shelter from wind and heat or to provide an enclosd space to contain warmth.
Trying to argue that hunting/gathering wouldn't work isn't too hard. I'ld make character roll just to ensure they don't choose poisonous foods.
Foraging/Survial by climate suffers from the fact that some places can have two or more climates (e.g. NZ where I'm from)
and multiple terrain types (e.g. NZ). New Zealand crosses sub-tropical and temperate zones.
Anyway, must save my words so I can babble more later and you're probably tired of listening to me.