UPDATE: I have been running about and figured that the top two locations for Birch Bark are Ravine and The Birch Forest that surrounds the Lonely homestead on Pleasant Valley Map.
LITTLE KNOWN FACT: I've watched a lot of playthroughs and almost everyone completely ignores the Cattails that are due east (if you are lonely homestead, look to where the closest waterfall is. THAT IS WEST. Go the opposit direction between two rock outcroppings.) of Lonely Homestead. Over there is a marsh area that is rich in cattails. It's fairly isolated and since I started visiting it, I have yet to get jumped by wolves.
Of course, I just jinxed myself.
Of the two, the Ravine Map is superior to Pleasant valley birch forest, both because of the lack of predators, and because of the close proximity to shelter. However, numerically, PV seems to beat out Ravine in NUMBER of birch bark harvested. (But not by much).
Just another reason why Ravine is my Cabin Fever recovery/must-see vacation home-away-from-home/tourist trap.
Oh. And now that I have been playing Interloper more, My estimates of "Effective" Harvest numbers of Birch Bark tea have dropped. I'm lucky to get enough birch bark on average to equal one cup every three days. I dunno if it's a Interloper thing. or what.
Frankly, I am using BirchBark tea as "Compressed Fluid" not really as a healing agent.
For example. Birch Bark is .22 water, but .1 weight. AND it can have up to 125 calories a cup. The 2? points recovered (I'm sorry. Since they took away the EXACT condition percentages, I'm having a hard time determining the EXACT amount of healing) is not much, but I have figured out something:
If I'm going to be traveling, and I drink a hot cup of Birch Bark right before I go, and the weather allows me to remain above freezing, and maybe I eat a Cattail before hand, I believe I recover 3 points total? 3-Ish? Which seems to translate into 3 hours of starvation, I can get away with. In the beginning of Interloper, before I get situated, I tend to see-saw between Starvation living and Well Fed, depending on my plans. Well Fed for shipping and long distance traveling, Starvation when settling down in an area to get crafting done. That sort of thing.
I recommend hording Birch Bark tea, until it is time to travel long distances. With the low weight to water ratio, the token calories, the fact it can be heated, and the minor amount of healing, means it is vastly superior to any other fluid, including water and soda.
Since you can drink one every 2 hours for full effect, I recommend it mostly for Interloper, where the higher thirst rate makes it, ironically, much more useful.
Effectively 3 cups of birch bark replace .66 liters of water. And 2.5 cattails. So, in theory, you could drink one every 2 hours while traveling. So it is possible to JUST take BBT with you and save on the weight. However, I don't think that's the best way.
I suggest instead to carry .5 liters of water for every 1 BBT. Upon waking up sleep, drink 1 cup and max out with the water, if you aren't at max condition. If you are at max, save the cup and starve for a bit, drinking it as the day goes on to remain hydrated. Figure on using it around 2 hours, ten minutes after waking up on interloper. The thirst rate seems to out pace the BBT by ten minutes, so you should carry SOME water around.
Although, I am experimenting with 2 BBT for every .5 liters of water. Drink one waiting up, max out thirst, a second cup at 2 hours 10 minutes.
Soda MIGHT be a substitute for water, IF you are trying to maintain Well Fed. Soda weighs .25 for .22 of fluids. So from a strictly fluid perspective, soda is the worst. However, if you are TRYING to maintain your calories, then it is a candidate for Water replacement.
Not everyone uses my play style (which is, first thing, power level cooking), but if you do as I do, then use BBT alone for long trips, and combine BBT and Soda for long trips when you are trying to keep the Well Fed Bonus. Which means, save up your BBT and Soda for the right time.
YES, I know, popular wisdom is that Soda never causes food poisoning. Well, I'm here to tell you I finally got food poisoning from a can of 6% soda. It doesn't happen often, but it does. Because soda spoils so quickly outdoors, I recommend, if you are stock piling soda, to wait until you have cooking 5, just in case.