Underdark Ecology

[s/LaSH]

The big problem with fungi is, as stated, biomass. You can't expect to have a couple of pads of fungus in a cavern and have that support an entire ecosystem. What you need is a more surface-style ecology. That is to say, most of the caverns are choked with fungi, and rock is rarely seen.

In this way, biomass is at a high level; fungus can reclaim dead bodies, be eaten by fungivores (fungi aren't plants), and then by carnivores and monsters. There would be very little left to rot in the caves. Note that fungi are pretty high in protein and chitin.

Because it's not a plant and has no woody fiber, fungus seems incapable of reaching the heights of the tallest trees (I'm not sure how far the chitin in its structure goes to support mass). However, it can easily climb above your head, and if species dealing with calcium (bones) have evolved, they might attain a metallic kind of trunk structure. Many regions, the fungus would probably just cover the ground like grass in between clumps of really big fungi; grass is flexible, fungus isn't, so walking over it will leave a heck of a trail.

Atmosphere is a concern. There will be virtually no weather systems in the Underdark, simply because of all the winding tunnels and lack of sunlight to baffle and deprive the system of energy. If a region has no oxygenating fungi in it, the air will stagnate and quickly become unbreathable. Diffusion from neighbouring areas will not be enough, because the air is so cool and still. It could take centuries to reoxygenate if there's no life there. There are a couple of solutions to this. Volcanoes in the lower regions heat air; if they operate on a tidal cycle, something vaguely similar to katabatic air currents might spring up as they 'pulse' hot air up once a day, creating an expansion pulse that could affect caves for miles around. The compression pulse as the air cools would likely be less violent. If the volcanoes were close and in series, they might create a sort of stuttering global/tidal shift of atmosphere that sets up an even better circulatory system. Another idea is massive, massive organisms living within the crust of the planet, probably older than land-based life, growing to miles in size and occasionally breathing. The 'blast zone' around their gills/air pores would be untenable for all but the hardiest lichen, but a couple of corridors away the fungi would be going, 'ah, a breeze of CO2, how nice'.

I think I think too much...

 

[MerakSpielman]

Real caves "breath" a bit - rock is slightly porous, and there's always a way to the surface. Variations in air pressure create air current which, though slight, keep the air more or less breathable in all caves on earth (unless there's no surface access or some other toxic gas present). Oxygen is still replenished more slowly than on the surface, though, since you don't have plants to recycle the CO2.

In a magical world, where you have tens of thousands of oxygen-breathing humanoids in a cave, you might have a magical version of fungus that recycles CO2 into breathable O2.

The temperature is stable all year round, since the heating and cooling influence of the sun is virtually eliminated. The air-circulation serves more to equalize air temperature than to bring cold-hot air from the surface. I belive the constant temperature at the bottom of Carlsbad Caverns is around 55-60 °F - but that's going on memory from my visit there years ago.

Food would be scarce down there. Fungi require moisture and nutrients to thrive. Most cities will be located next to a river or lake, since it's hard to dig wells, and probably have fungus-farms based on the river ecosystem. Underdark Druids probably have a Fungus Growth spell that can increase the yield of such farms substantially. Since there are no seasons, fungi can be grown year round.

A tremendous volume of supplies for Underdark civilizations are probably imported from the surface as trade goods in exchange for mineral wealth. Clerics might spend a lot of time casting Create Food and Water to ease the expense of supporting their temples.

Economy-wise, mineral wealth would be less valuable than it is on the surface, while such mundane goods as cloth, rope, leather, wood, paper, beer, spices, and any other product based on plant growth would be in great demand (leather isn't itself plant-based, but you need pastures for cattle).

It would be beneficial to have a rapid way to the surface for raids, trades, etc... Perhaps there's a few permenant teleportation circles set up?

To steal an idea from Morrowind, Underdarkers might cultivate giant ants (who would have their own surface access) and harvest their eggs and larvae for food. Some ants collect a sugary liquid that could be used as honey, or brewed into liquor.

Cities would throw nothing away. Waste (i.e., sewer waste) would be collected and used as fertalizer. It doesn't take much to get a good, stable rat population growing. Underground lakes and rivers would be heavily fished - probably with nets strung across the entire width of the river to catch any edible thing that might have washed down from the surface.

Goblinoids/Kobolds (and similar filthy species) probably eat other humanoids if they get a chance.

With the plethora of evil races, and the scarcity of food, undead labor becomes attractive. Skeletons and zombies never tire, never talk back, can perform basic tasks, don't need sustenance, and can be pressed into service as shock-troops at a moment's notice. In fact, they'd probably be cheaper than slave labor, which is what the evil races are generally portrayed as using. Commonplace undead-raising also helps solve the problem of what to do with dead bodies when space is at a premium.

Pack animals (for trade caravans, etc...) might include giant lizards and monstrous spiders.



Just a few thoughts! Hope I helped!

 

[I'm A Banana]

Well, aside from buying Into the Black or Underdark, which have a LOT of detail on the ecology and conditions of the underground (especially Into the Black), I'd basically imagine an ecology based on mushrooms and fungus instead of green plants, devoid of large herbivores, and replete with insects and arachnids of various styles and sizes.

 

[nikolai]

Anyways, I am planning on having the players venture to the Underdark shortly and I am trying to think of a way to explain the ecology of the Underdark...

Here's my suggestion; it's not what you asked for, but it may be worth giving a second thought to how you go about constructing the underdark. There's no need for an "ecology" in the conventional sense. It's anachronistic; the whole idea of food chains and nutrient cycles is very modern and alien to this sort of fantasy environment. It's also difficult to import these ideas and make them work; the reason there aren't vast underground cities supported by fungus on earth is because the real world doesn't work that way.

So why not use medieval ideas instead? For example, there was a division between higher creatures (people, dogs, sheep, lions, etc.) and lower creatures (spiders, snakes, worms, insects, etc.). Higher creature reproduce in the usual way, but lower creatures were spontaneously generated from matter. So they just automatically come into being from water, earth, rock, filth, decomposing organic material, or whatever depending upon the creature being generated. So ecosystems which would be impossible by modern ideas, could be sustained logical this way.

It seems a way to explain the underdark, but not generate fantasy and campaign killing problems.

 

[monboesen]

In my latest dungeon crawl I started with bacteria. Bacteria can derive energy and therefore live of almost anything, even inorganic minerals. I decided to go with hot springs, not unlike what you find in the deep sea.

The mineralfilled water in my cavesystem originates from vulcanic activity deep under the mountains and wherever it leaks out into caves and tunnels, thick patches of brightly colored bacteria grow. They in turn are grazed by slugs and insects, whom are predated by large insects/animals. Fungi live of both bacteria and dead slugs/insects/animals.

My "underdark" is only sparsely populated. Consisting of long stretches of barren rock linking oases of life dependent on the scolding water.

Goblinoids live in these deep caves, and have developed a kind of agriculture based on the bacteria. They build shallow tanks and have pipes that lead the water there. In the tanks they keep giant slugs that they eat. They also grow and cultivate several species of fungi for food. Any dead goblin is, as part of their burial ceremony, dumped in the watertanks.

They still raid the surface for other kinds of food and covet real meat (be it human or animal). But they can survive solely on their own foodproduction.

As for oxygen, I did not really give it much thought, but it could be a wasteproduct from some of the bacteria, depending on the minerals they "eat".

The point of it all is. We, on the surface, have a diverse and large group of organisms (plants) that can survive and produce biomass from inorganic nutrients and solar energy.

The bacteria can also survive on inorganic nutrients, if they have an energy source. But that energy can come from inorganic materials as well. So with a large enough supply you could in theory have a diverse and high biomass ecosystem not dependent on the sun.

Well enough rambling. I hope this is in some way useful to you.

 

[DM Storn]

Thanks again folks for the terrific responses ... this is great stuff! I am certainly glad I found this forum


DM Storn

 

[glass]

How about a large monster that tunnels through rock, digesting it and giving off oxygen? That would kill two birds with one stone, by explaining how people breath and why there are so many conveniently sized tunnels.

BTW this is not my idea, I have a vague recollection was actually in one of the 2e Monstrous Compendia. Can't remember which one but I would guess Greyhawk.


glass.

 

[MerakSpielman]

You could use delvers for this if you wanted.

 

[Hand of Evil]

I say think circle of life, listing out each group.

12 o'clock top of the chain - Mind-flayers
01 o'clock what the Mind-Flayers eat and prey on - Drow, other...
02 o'clock what those at 01 prey on, you can be nasty here and say something like trogs. Hey they are evil in the underdark and the eating of other races would more than likey take place.
03 o'clock what those at 02 prey on - gaint rats, gaint insects, eggs from gaint lizards...

What you need up with is your ecology and a ramdom encounter table.

Side note: sometime ago I posted a link on the use of waterway in the creation of a hydroponics that was used in Pre-Columbus South America, four feet wide by four feet deep waterway surrounding growing area four feet wide, repeat, use terracing (small degree) to move the water downhill.

 

[MerakSpielman]

You know, beholders are probably up there above humanoids, too, maybe on a par with mind flayers. Not sure where the Yuan-Ti fit in.