Does in make sense in a Fantasy Setting to make Survival a skill by terrain. Desert, Forest, Plains etc. Or will this be too much spend for players.

As in a survival skill for each type of terrain rather than a "blanket" skill?

Yes, it makes a lot of sense since a desert dweller that has barely visited a forest will only know how to survive in a desert.

As long as the same rule applies to everyone at the table, that's a very interesting option, However, by using the background of where the PC has come from, you can apply several setback dice, increase the difficulty or upgrade the check if the PC is from a desert environment, but is tracking in snow for example.

The system should be made simpler not harder in my opinion.

Right, Hooly. That's how I would do it. Select your home terrain (Desert, Snow, Grasslands, Jungle, and Underground/Dark) and any terrain outside your home terrain gains one or two setback dice depending on just how different from your home it is.

I think it makes sense to customise the rules to suit the setting or type of campaign that's being run. In this instance, exploring different landscapes and environments could be a core part of the experience so it might make sense to split Survival up. You could even be in situations where you need to hire an NPC to help guide you through a desert/swamp/etc if a group has never had any experience in these situations.

If you don't want to have separate skills, you can always impose setbacks for unfamiliar terrain. Alternatively, create a talent (probably Tier 1 or 2) that grants a boost for a single type of terrain if you want to allow someone to specialise in a certain environment.

Survival is pretty universal regardless of terrestrial environment. I'd be more inclined to use Setbacks and Boosts, if I even bothered, than to nitpick each one as a Skill.

If I felt compelled to do this at all (in some kind of world-spanning fantasy game), I'd go by climate: arctic/temperate/desert/tropical.

No, I don't think it would be helpful.

1) It creates a boatload of skills, something Genesys does not seem to favor.

2) Survival is survival. Personally I have some survival skills learned in Maine (cold forest when I was there) and lived in the Mojave desert for a decade camping often and rock climbing. The skills are basically the same. If cold, don't sweat, drink water, keep core temp. level, risk vs. reward on caloric costs, etc....knowing oleander bad or amaranth good is inconsequential, knowing how to test if either plant is bad or good is universal.

Another option is have a talent than focuses on a terrain type, adding advantage when in it, or whatever.

Just my two cents

Yah I agree. It creates bloat. Are Melee Light and Heavy enough? Should we have blunt, piercing and slashing sub categories? How many different martial arts should there be, etc.

So do I, any specialisation, if at all, should come on top; i.e. in the guise of a Talent that removes Setback/adds Boosts.

I'd do it as a Tier 1 talent. Home terrain: Choose from Desert, Forest, Plains etc. When making a Survival check while in this terrain, decrease the difficulty by 1 to a minimum of easy.

I think this is the correct option. It allows a character to spec into a specific terrain without contributing to skill bloat, and even if you don't put points into the skill the character still has an easier time with the terrain. You could even make it a ranked skill, or put an "improved Home Terrain" at Tier 2/3 with some additional benefits.

Plus, as a Tier 1 talent, a player can do a flavorful dip into it, or have it be put into a career/species template.

I'd say it depends on what you want to be focus of your campaign. If it is heavily survival related, then yes, own skill to every environment, at normal game, where focus is at somewhere else, it's not worth it in my opinion. Rather than separate skills, I'd make it so that player needs to choose a focus for survival, and maybe gain boost to it, and setback for other terrain/climate types. Maybe custom talents to buy new focuses?

Disclaimer: I haven't yet gotten my Genesys so I cannot comment anything unique to it, but I have quite much experience GMing FFG SW (nearly 100 sessions). And before FFG SW game, I GMed a game where there were separate skill for almost everything imaginable. Currently I value universal skills, and IMO FFG SW has fairly good skill coverage.

The Talent's not a bad idea, but even that shouldn't be necessary. The character's backstory should make it clear where they learned their survival skills; using Survival there gets no penalty. Other terrains get 1 or 2 Setbacks, which will disappear if the character rolls Triumphs and cashes them in on new environmental expertise, or if the character spends enough time there at the GM's discretion. (In a sense, this is the same as GURPS' "familiarity" rules.)