Ykhjuy

I have an alien planet with the entire world landmass arranged in two giant rings roughly 10 degrees north and south of the equator. Everything above sea level is beach or tropical rainforest. The rest of the world is ocean. Other than these main details (plus whatever secondary effects such conditions would have), the world size, atmosphere, chemistry, etc. can be assumed to be Earth-like.

Flora and fauna on this planet have evolved in a manner consistent with Earth. (e.g. fish here are functionally the same as fish on Earth, with only minor/cosmetic differences) The main difference is the significantly-reduced variety of life present here.

The human-analogous alien population sit comfortably at a tech level where they can exploit their natural resources, and global trade is commonplace, so for the purpose of this question, all native foods and food ingredients are available anywhere on the planet.

A ship of Star Trek-esque interstellar humans have landed on this planet to sample the planet's cuisine and restock their food supplies. Considering the limited nature of the planet's resources, what is the range of food types they might find here?

I imagine fish and tropical fruit would be commonplace. Meanwhile, any kind of plant that can't stand heat or humidity would be non-existent, which means there probably aren't any grains to produce baked goods like bread from. If I want to avoid inventing wildly fantastical alien flora to fill out the menu, is fish with jam the only thing my explorers are going to find here?

A little reality first :

This world's biochemistry would, by definition, be completely alien, so there's a very good chance everything could be poisonous or carry infectious organisms, at least as far as the visitors are concerned. Even breathing the atmosphere could potentially be lethal as it may carry airborne bacteria and other small organisms, never mind be toxic in some way (too much oxygen can even kill).

This works the other way as well. The visitors could introduce their alien organisms, parasites, bacteria, etc. to the world and it's inhabitants. Even in human history there are multiple examples of visitors from one place visiting an area previously isolated from them which resulted in one or both passing a disease on to the other than they had no defense against. And that's just within the same species and planet - the dangers of actually meeting completely alien life are pretty hard to estimate to quite real.

What kind of food ...?

Well as you describe it it would be very strange if the natives did not exploit the sea where it was possible. That would be the norm along the coastal areas. The areas inland where travel to the sea was not a realistic daily option would probably undertake agriculture of some sort and possibly trade with the coastal regions for e.g. dried sea foods.

However how diverse and what kinds of food would be possible is impossible to say. We have only one example of life (Earth) and from what we can tell life will develop and adapt to a wider range of conditions that even the surface and sea provide normally. There's really no way to say how your vaguely outlined planet's life might be, except that it would be surprising if it were not equally diverse and complex. What food humanoid natives might make from that is beyond guess work.

But the visitors would have to be extremely careful to manage potential biohazards from trying to eat the natives' food.

Meanwhile, any kind of plant that can't stand heat or humidity would be non-existent, which means there probably aren't any grains to produce baked goods like bread from.

Your natives would doubtless have something that fills the role of grain and bread for them. Plants grow in all sorts of extremes of heat and humidity just on Earth, why would this not be the case on your world ? If memory serves me Cassava Flour is used to make baked food stuffs in e.g. Brazil. It's gluten and grain free, AFAIK.

is fish with jam the only thing my explorers are going to find here

Fish would again be off the menu for any but the most suicidal explorer. Jams are a way to preserve fruits and while they're probably less dangerous in terms of biological infection, they'd be just as dangerous in terms of potentially toxic side effects for the visitors.

You're also neglecting all sorts of potential food stuffs (for the natives). Insects are one example. Again the wide range of what qualifies as food for humans just on Earth is limited only by personal taste and whether we've figured out a way to eat it safely. Heck we drink alcohol and that's a poison ! Likewise caffeine. If offered a drink by the natives the odds are high it would at best make the visitors ill and at worst kill them instantly.

We cook foods to eliminate most health threats in food. However just because the natives handed the visitors something cooked does not mean it is safe for the visitors. It could still contain chemicals and even bacteria and other organisms which don't affect the natives at all, but would be extremely dangerous (or lethal) to the visitors.

Stephen's Rules for Planetary Exploration :

1. If it goes down to the planet it stays there, to avoid infecting the ship. That includes people.


2. What goes down has to be sterile (meaning lifeless, not just clean).


3. Look, don't touch. We have sensors, we use them.

Those clearly aren't TV rules !

It can be anything you want

The conditions you have specified do not greatly restrict the ways that life could have evolved; all sorts of stable ecosystem solutions are available, including ones that we could never even imagine. In fact the number of possible alien solutions is so large that it is unlikely that anything will even slightly resemble anything you have ever seen before.

However "beyond all imagination" is not very helpful for writing, so most people stick to the trope of getting exotic things from the real world and tweaking them to make them a little less recognisable: the floral equivalent of the man in a rubber suit.

By the way,

which means there probably aren't any grains to produce baked goods
like bread from

is not correct. There are plenty of cereal or pseudo-cereal crops grown in the tropics. The most obvious is rice, but there are also amaranth, sorghum, millet, most varieties of maize, and probably many others. Amaranth might be particularly suitable to your story because the plant looks very different to conventional cereals. (For that matter, maize seemed very weird to Europeans when they first encountered it, but of course has now become familiar.)

Another small issue:

A ship of Star Trek-esque interstellar humans have landed on this planet
to sample the planet's cuisine and restock their food supplies.

The odds of the local life being nutritious to humans, and safe for us to eat, are probably quite low. The basic chemical structure of alien life could be very different to terrestrial life, perhaps not even water-based. There is an argument that basic polymer structures like carbohydrates and proteins are reasonably likely to have evolved more than once; but there is no reason that the monomers of these molecules would be digestible by us. All vitamins would almost certainly be missing, and there is a high probability that some of the biomolecules would be significantly toxic to us because we haven't evolved alongside them to develop detoxification mechanisms.

Your travellers will be better off growing their food in hydroponic plants on board their ship.