RAW is Perception or Survival, with Herbalism or Region Lore as complementary skills. So if you dropped Perception, it would be Survival as the skill for searching for natural things in a natural environment.
Which, if you think about it, makes all kinds of sense.
Maybe it comes from our way of thinking: there are (at least) two ways of learning how to do something. The first is by actually learning that particular thing. The second is by being immersed in an environment where you have to do that thing to thrive, even if you don't learn it specifically.
The first leads to one or more perception skills.
The second leads to one or more active skills that happen to include perception in the corresponding environment.
For those who don't mind the bookkeeping and the long skill list, having both makes sense (but then again, it would probably be better to have perception skills cost a fraction of the DPs of active skills to balance things out a bit).
For those who prefer to keep a short skill list (including specialties), then the second option is probably preferable.
The same logic can also be applied to knowledge in a number of cases. You have an apothecary skill ? You probably know something about herbs, and something about reagents as well, and a fair deal about poisons and diseases, and basic medicine, though at various 'equivalence levels' if you want to nitpick. You have a guard skill ? You certainly know how to look for suspicious activity, and to discern lies, but you also know the basics of the most common trade languages in the area, and basics of administrative work, and common trade routes and what usually is traded. This really favours a 'occupations as skills' kind of system, which I find easy to use but requiring quite a bit of on-the-fly judgment call (but then again, that's GMing for you).