"Survival" games can be, in my experience, difficult to run. Most players (for the D&D crowd, anyway) expect to fight monsters, get treasure, and thwart enemies (be they good or evil). Running a game where the goal is simply to survive can be a challenge. If you do it correctly, however, it can be a great game.
I am not familiar with this series personally (at least, I don't think so, the author's name sounds familiar...), but if there are few humans, then what pushes the story forward? In most "survival" stories, if the protagonist is not opposed to some intelligent life form, there are only a few other options:
- Man vs. Man
- Man vs. Machine (only a slight variation of Man vs. Man)
- Man vs. Monster (again, usually a simply variation of Man vs. Man)
- Man vs. Himself (inner conflict, but this would make for an unexciting role-playing game in most of the standard senses)
- Man vs. Nature (in a looser sense, Nature simply refers to the environment, including urban cities and the depths of space)
It looks like this last one is what you want. If you intend to run a 'traditional' style RPG (traditional, here, referring to one in which the players have both combat and non-combat encounters, and in which victory over said encounters provides some reward, whether it is loot, an escape, or at least some experience points), I suggest creating at least some sort of small settlement of people. It could be anything from a small village to a simple farmhouse where the players can return and rest, trade goods, etc. It is certainly possible to run a campaign without this, but you will need to make sure that the players have access to food, water, weapons, supplies, etc. in some other manner. Perhaps they stumble across a hidden (well, not hidden any longer) cache of equipment.
Also, the mechanics of such a game would be significantly different than any system with which I am familiar. The D&D 3.5 rules have very little to say about food, water, and sleep, other than explaining that most kinds of creatures require these things. You will need to modify and adapt these rules if you intend to run a survival game, or simply use a different system (unfortunately, I have few suggestions here).
So, to wrap up my overly long post, I'll say this:
- This sounds like a Man vs. Nature game
- The focus should probably be gathering/purifying food and water and collecting other necessary supplies.
- You should consider at least a few NPCs, even if it is just a single family in a farmhouse.
- D&D and d20 are not built to handle this kind of mechanic (eating, drinking, and sleeping). However, d20's Wealth system would work well as an abstract bartering skill, if you decide to use some NPC interaction.
And finally, a thought that just occurred to me, this game would be much easier to run in large tim increments, rather than small. Every week the PCs might have to trek out into the wilderness to find food for next week, making appropriate skill checks or bringing down a bear in a straight fight. You don't need to alter the mechanics too much for this, no- to low-magic D&D would work or the d20 Modern classes could be adapted. Although I suggest looking for a more appropriate system or playing a rules-lite game.
If you provide more details on what you are looking for, I would be happy to help more.