I've just started running Tomb of Annihilation, and the party are gearing up for their first foray into the jungles of Chult. From the equipment list, the focus on dehydration etc. I had assumed that managing supplies and water, and therefore carrying capacity or even encumbrance should be important.

One of the PCs is a Barbarian with the Outlander background. The Wanderer feature cuts all this out entirely, making worries about supplies and dehydration irrelevant.

I don't want to nerf the feature and therefore weaken the PCs niche, but does removing these elements hurt the campaign?

Should I possibly say that due to his unfamiliarity with the terrain it only gives Advantage on Foraging rolls for a while, play up the survival/expedition elements early, and then once that's gone from exciting to busywork say that he is now familiar and the feature is back to full effect?

Honestly,

It becomes pretty moot pretty quickly with magic.  A single Druid makes "Don't Starve" irrelevant.

It would cost the Druid two level 1 spells to create 10 Goodberrys (enough food for 10 people) and Create Water makes 10 gallons of water (enough water for 10 people normally and 5 people even in hot conditions).

Worrying about the Barbarian's Outlander backgrund making foraging too easy with Outlander just reduces the spell requirement.  It's nullified with a different mechanic.  Instead of 2 spell slots it's nullified at the cost of a background.

I will admit, back in 2nd Ed some of my hardest memories was playing "Don't Starve" the RPG.  Having to plan out each expedition, equipment, supplies, plus carrying animals and carts.

I would focus on the things the PC can't just magic out of thin air.  In the Tomb of Annihilaton they are going to need a LOT of supplies.  Recommend they get sherpas, a cart, a mule, to carry all the gear.

The players have made a party where the paladin is the only spellcasting class, so I hadn't thought much about magic.

I think I'll sweat the players for a few sessions for a bit of low level fun, and switch it back on after three of four sessions in the jungle.

Not having any full caster and a single paladin....   I think your party is going to die, horribly. :)

Foraging is on p111 of DMG.  Diseases are on p256 of DMG.

Sadly the diseases listed are all, super bad.  they don't have anything like dysentery.

I don't know if your party is old enough to remember the game Oregon Trail...  but I just had an idea.

You don't have to nerf the Barbarian's ability.  The ability lets you find water and food, but it never says the water has to be totally clean.  If they don't take supplies, porters, carts, with them... then just make simple checks to see if any of the water they find is contaminated.  The Rogue might die from dysentery.  The Paladin by level 2 can cure Disease, but it will use up a lot of resources and that will push them to plan more effectively in the future.

Jungles are just awful places to be in.  Remember jungles are difficult terrain, so the party are going to crawl across the map.

Unless your Barbarian PC is from Chult, I would argue that her/his ability to use the wanderer feature is not so simple. Based on a strict reading of the feature, it seems to apply mostly to areas they already know.

You have an excellent memory for maps and geography...

I'm not suggesting you disallow the feature, only that it may not work as perfectly out of the gate as it would if she/he were in their "home" area. For example, perhaps for the first couple of days he/she must make a survival check vs a low DC of 5 or 8. Failure doesn't mean they find nothing, but perhaps just the barest minimum, leaving them hungry or thirsty, but alive. If they fail two in a row, the party gets one level of exhaustion. Over the course of the first couple of days, the barbarian starts to learn more about the area until he/she really starts to identify the good from the bad for eating drinking, and then the feature works as usual.

If you don't want to have them make checks, let the feature work as usual, but make them play it out so its not book-keeping. Yes, the barbarian can located food and water, but when they find it, there are dinosaurs or undead there they must defeat before they can eat!

As for a Druid's goodberry canceling out the need for bookkeeping of survival, I'd argue that it is balanced by the need to use up previous spell slots.

mjsoctober,

you're forgetting the other half of the ability

In addition, you can find food and fresh water for yourself and up to five other people each day, provided that the land offers berries, small game, water, and so forth.

That said I agree with your conclusions.  A lot of it comes down to how much book keeping the party thinks is fun.  I've played a lot of games where the planning for the book keeping was a lot of the fun and adventure (because you really think of your characters as people when they have to do things like sleep, eat, and *@% in the woods).  That could just be me and I'm weird... I also like speadsheets and am usually the "Party Treasurer"

@FMB, I didn't forget, I think it's logical to conclude that the feature is meant to work in an area you know. If you travel to a new place with some very different flora and fauna, you wouldn't yet know which ones are safe to eat, and which aren't. You'd have to ask locals, study predators and prey, watch which plants animals eat, or which water holes are safe. You'd have to learn the new area. I think it's completely logical for a DM to require a PC with this ability to learn the new area.

"In addition, you can find food and fresh water for yourself and up to five other people each day, provided that the land offers berries, small game, water, and so forth."

I don't think the Outlander ability to find water is very useful in Chult. The PC will have no problem finding water. However, ALL groundwater is contaminated with bacteria, parasites and other jungle diseases. The Outlander skill will only allow the character to find something that exists. If there is NO potable water in the jungle environment (which may well  be the case) then there is NO way for the character to find something that does not exist since the ability does not allow for the magical creation of food or water.

This is why the ToA rules provide rain catchers for purchase. Direct rain water is the only water that can be consumed in the jungle without boiling.

As one of the other posters mentioned, there are a number of easy ways around the problem of food and water. Create water, create food and drink, goodberry and perhaps the easiest Purify Food and Drink (this one is available to the paladin if I recall). So an organized party with the right kind of spell caster is unlikely to have a problem. However, if that spell caster is incapacitated or otherwise unable to create safe food and water the party could run into trouble very quickly if they don't have backup supplies and rain catchers.

As was listed earlier.

 In addition, you can find food and fresh water for yourself and up to five other people each day, provided that the land offers berries, small game, water, and so forth.

Of course, this dictates that the land must have it available. As was stated before finding food and drink and rendering it safe to consume are not the same thing. Now a good guide should be able to tell characters to boil water, and collecting rainwater is always safer than drinking groundwater. Any meat they eat should be cooked until the juices run clear to prevent parasites. That's just the real world stuff too. Remember that to forage you have to move at a slower pace, nothing in Outlander says you can find the food while traveling at a normal pace. I have to concur though, ToA with only a Pally is a good way to kill some PCs. Paladins are a good mix of offense, defense, utility, and healing but they are not life clerics or even grave clerics. They are going to be resting a lot (which can trigger random events) and long rests don't give you back all your HD even if it does refresh your HP. Chult is a dangerous place, moving slowly to find food and stopping frequently to recuperate will make traveling the jungle very slow and even more dangerous. Good luck to your players. 

Now for a quick aside on why Outlander can find food and water in areas they have never been before. As one travels one will see beauty and wonder. Nature and the world are vast and complex, and once you have seen one tree they all look about the same. Water flows downhill, from one source to another. Game trails lead to water in one direction and to food in another. Moss may not always grow on a specific side of a tree but trees are great places to check for birds nests and eggs. Assuming something is not affecting/duplicating/redirecting/or misaligning it, the sun typically sets in one direction at night and rises in the other the next day. While areas may be different, and the ground underfoot new, the world is the world and it follows its laws. At least usually, I mean...come on, there is a cat-man walking around the port playing the ukulele, weird stuff is going to happen. So don't drink the groundwater, cook your food, and assume anything you encounter is going to want to kill/eat/desecrate you and/or the parts that used to be you. 50 GP seems cheap when you are bleeding out. 

Foraging p11 of the DMG says you can Forage while moving at normal or slow pace.

Travel Pace p182 of PHB says you travel 3 miles an hour or 24 miles a day at a normal pace and 2 miles an hour or 18 miles a day at a slow; halve these numbers for Difficult Terrain.

The benefit of traveling at a slow pace is they can attempt Stealth.

In addition each party member can do one other "Activity" while moving these are:

• Noticing Threats
• Navigate
• Drawing a Map
• Tracking
• Forage

Over all I think this is well balanced.  the Barbarian's ability means they can provide food for the entire party (it's a small party).  This leaves other members available to do other tasks like Tracking, Navigation, or Noticing Threats.

for completeness IF you have a Ranger in your party and they have Favored Terrain: Forest

While traveling for an hour or more in your favored terrain, you gain the following benefits:

• Difficult terrain doesn’t slow your group’s travel.
• Your group can’t become lost except by magical means.
• Even when you are engaged in another activity while traveling (such as foraging, navigating, or tracking), you remain alert to danger.
• If you are traveling alone, you can move stealthily at a normal pace.
• When you forage, you find twice as much food as you normally would.
• While tracking other creatures, you also learn their exact number, their sizes, and how long ago they passed through the area.

@FullMetalBunny

Thank you! I think I was misremembering the foraging rules, that or I was taking into account the difficult terrain of Chult or thinking of the reduced speed/exploration effects from ToA. Not sure. Anyway, thank you again.