Wetlands - What They Are and How To Use Them

Bog, swamp, marsh, fen. If you’ve ever wondered what the difference is, then this is for you. We’re going to look at each one and see, on the technical level, what the difference between each type of wetland is.

After that, we’ll look at some more ideas for world building, like local resources and hazards, and we’ll finish off by looking at some legends associated with wetlands.

By the end, you’ll be a wetlands expert and able to make better ones for your worlds. Let’s jump right in.

Types of Wetlands

The main types of wetlands can be broadly separated by their water source and the types of vegetation that grow there. If you know these two points, you’ll be able to correctly identify the types of wetland you have.

Tidal Vs Non-Tidal

Before we get to the main types, it’s important to get one piece of terminology out of the way. That is a tidal and, its opposite, the non-tidal wetland. As you can probably guess from the names, the difference between these is where they get their water from.

Tidal: Tidal wetlands get their water from the ocean; they are coastal areas that become flooded as tides roll in. This means tidal wetlands have brackish or saltwater. This leads to unique flora and fauna living there that are adapted to the salinity. They are found along coastlines, as you might have already guessed.

Brackish - Salty waters where the level of the salt (salinity) is between that of freshwater and seawater. In increasing amounts of salt: Fresh water -> Brackish Water -> Salt water

Non-Tidal: All other forms of wetlands are going to fall into the non-tidal category, that is they get their water from places other than the sea. This also means that they are going to be freshwater instead of saltwater. They can be found all over; we’ll get into how they form a bit more in the next section.

Now, keep in mind that the line between these can be blurry. Some wetlands might have both a tidal and non-tidal source of water. In some cases, this might be a permanent state, but other things, like strong storm surges or human activity, can create a temporary mixture.

In general, most wetlands are going to be of the non-tidal variety simply because they have more options for how they’re formed, and a wider range of areas in which they can form.

Marshes

Marshes are areas of land that are always or mostly covered in water. This water is usually fairly shallow. Most of this comes from surface water; things like river runoff, precipitation, or rising groundwater levels.

Marshes are home to a variety of soft-stemmed plants like reeds or grasses that are adapted to the high moisture environment. Animal life can be plentiful, with larger marshes home to a wide variety of species.

Marshes can be both tidal and non-tidal. Tidal marshes are often called “salt marshes”, which makes sense.

Example: The Everglades (sawgrass marsh) in Florida, USA.

Swamps

Swamps are wetlands that are dominated by woody plants like trees or shrubs. In fact, swamps are usually categorized into forested swamps or shrub swamps depending on the dominant foliage. These aren’t mutually exclusive, though, and oftentimes you’ll find both next to each other.

Like marshes, swamps get most of their water from surface water sources like precipitation and river run-off. Swamps often have deeper and more persistent water than a marsh, though. While marshes might see long periods of dryness, swamps are often waterlogged permanently, with standing water being present year-round in many cases. Swamps can also be tidally fed when coastal.

Example: Sundarbans in India

Bogs

Bogs are peaty areas of acidic waters with floors of sphagnum moss. Bogs form when the decaying matter and moss traps in water. Because of this, bogs are mostly fed by precipitation. Many bogs form in glacial depressions as moss and decaying matter take over.

These factors all mean that bogs are generally nutrient poor and retain water for long periods of time. Bogs are primarily found in the northern hemisphere. The mix of cool, wet climate and glacial activity makes it the prime area for bogs to form.

Bogs are important as they absorb water and prevent downstream flooding. They are also home to a variety of species that are adapted to the acidic nature of the water. Some varieties of pitcher plants, for example, only grow in bogs.

Example: Bjældskovdal - Denmark

Fens

Fens are similar to bogs in that they are peat-forming wetlands, but differ in how they get their water. Unlike bogs, fens get most of their water from runoff or groundwater. This makes them much less acidic than a bog, which means they support a wider variety of animal life.

Over time, as more decaying matter builds up, it’s possible that a fen becomes a bog. This usually happens when peat builds up and cuts off the fen’s access to groundwater.

Example: The Great Fen - UK

Mire

I wanted to add mire here, even though it’s not technically its own wetland, because it is used so frequently and would be helpful to know. Technically, it’s a broad description that includes both fens and bogs. So when you hear mire, it’s usually referring to one of those two wetlands.

Resource & Economy

Now that we understand the different wetlands we might include in our worlds, it’s important to consider how they might fit and what motivation people have to live there.

Of course, you can always use the “inhospitable swamp” trope, there’s nothing wrong with that. Wetlands can be dangerous, remote places with little reason to explore them. However, I think it’s more interesting to consider the scenario where people do live near the wetland.

To help with that, let’s go over some of the key resources and reasons that people might live near a wetland, or interact with it.

Bog Iron

Bog Iron is a form of iron that forms in wetland areas, in particular bogs, hence the name. This could then be harvested and forged into weapons and tools.

While implements made this way were more brittle than traditionally mined iron, they had the advantage that it was quicker and easier to use bog iron over alternatives. In some regions, mostly in the north where bogs are more common, bog iron was the most commonly used method of iron tool/weapon making.

Bog iron also has the advantage that it is “renewable” in a sense. Once an area has been bled dry of its iron deposits, it only takes about 20-30 years for it to naturally replenish. This isn’t instant, but depending on the population and size of the bog, it might be quick enough to effectively never run out.

World Building Example

The Manuia are a group of several small tribes with a shared culture who live in and around the Great Bog. Here, they harvest bog iron to create tools and weapons. They largely live off the land, frequently moving about the wetland as deposits of the iron wane and replenish. For what they can’t harvest, hunt, or grow themselves, they trade their iron implements with distant towns for; making the trek as a trader is seen as a right-of-passage for young men.

Peat/Turf

Peat (turf) is a natural fuel that has been harvested from bogs for thousands of years. It was particularly popular in Ireland and Scotland, and served as a good fuel source where trees were scarce.

The fuel forms in waterlogged conditions from decaying plant life, particularly the sphagnum moss that makes up bogs. Once dried, it turns into a long-burning fuel that has a very distinctive smell.

Peat has been a historically important fuel and didn’t start to see decline until the Industrial Revolution. It’s still used in some parts of the world today, but is largely being phased out due to environmental concerns.

World Building

One of the most important resources for the Manuia tribes is the peat they harvest for fuel. Trees are scarce in the bog, and the few that are there are often used to make shelter or tools. This leaves the peat as the primary source of fuel. Warriors from the tribe venture nearly every day out into the swamp to harvest the peat. This ensures there is a constant supply. This is especially important during the colder months when long adventures into the bog are impossible.

Transportation and Trade

Some wetlands with access to the other waterways can also function as trade routes. Connections to rivers or out to the ocean can make a swamp a strategic area that connects inland areas further afield.

If going this route, bear in mind the logistics of it. The wetland will need to be deep enough and persistent enough to allow consistent navigation through it. An unnavigable swamp is of little use to those looking to it as a trade route.

You might also consider having the swamp be the source of a resource, such as fish or fur, and have traders travel from it out to other towns.

World Building

The Twisted Glades swamp has long been a confusing labyrinth of shallow streams, thick foliage, and dangerous inhabitants. Recently though, a daring trader was able to make his way from the head of the swamp, where it’s fed by a mighty river, out to sea. This is the first time it’s been successfully navigated, and it opens up immense opportunities for trade. All the local powers are now eyeing the swamp and working to swiftly make their move to stake claim over it.

Fertile Soil

The rich, decaying-matter filled soil that wetlands hide is often filled with nutrients and is perfect for agriculture. This made wetlands popular places for farmers to want to grow their crops.

During the Middle Ages, many wetland areas in Europe, and elsewhere, were drained for just that purpose. Using a variety of water management techniques, people would drain swamps and prevent them from refilling with water. This would leave behind fertile soil, perfect for agriculture.

Other Resources

Lastly, I wanted to quickly go over some other resources that people might find in a wetland area.

Wood and Reeds - Important for construction, housing and otherwise. Wood has a large variety of construction uses, and reeds were often used to make thatched roofs, insulation, or baskets.

Food - Many wetlands are filled with life, perfect for hunters. Deer, fish, birds, and eels are just some examples of food sources available to wetland hunters.

Fur - Fur is another big resource found in many wetlands. Various types of wetlands are key habitats for animals like beavers and muskrats, both prime targets of fur trappers.

Clay - Wetlands are also a source of clay. Potters in the Middle Ages would often dig up areas of wetlands in order to obtain usable clay.

Salt - If your wetland is tidal, it can also be a location to harvest salt from. Using various techniques, people are able to remove the salt from the water. Salt marshes were an important source of salt during the Middle Ages.

Hazards Beyond "Difficult Terrain"

It’s easy to see a wetland as “difficult terrain” and slow to move through, or home to the legendary swamp beast. But what other sorts of dangers might be present? In this section, we’ll look at some broad ideas for introducing danger into your wetlands that aren’t just combat-related.

Disease

Wetlands are notorious for being a hotbed of disease. Mosquitoes use wetlands to breed, which only furthers a disease's propensity to spread. Malaria is a deadly example of one such disease.

Having the threat of disease can be an interesting way to challenge a group of players without using combat. Having them need to expend resources preparing for a disease-filled trek through a swamp, or having them deal with the consequences of a lack of preparation, are both good ways to test the players.

Gas Pockets

As matter decays in bogs and other wetlands, it produces methane. This can lead to gas pockets in the swamp, where trapped methane is able to escape into its surroundings.

Methane is highly flammable, so a lit torch or fireball spell can set off a chain reaction of explosive consequences. It’s also odorless and colorless, making it the perfect trap.

That’s just one example of “swamp gas,” but there’s no reason you can’t branch out from there. Maybe a gas that causes hallucinations is leaking from the decaying corpse of a magical beast? This is a good way to take a real-life, grounded occurrence and twist it to be a bit more fantastical.

Insects

We mentioned mosquitoes above, which are a threat on their own, but they’re not the only insect danger in the swamp. Things like centipedes or even ants can be deadly, especially in large numbers.

You can also play on the psychological health of the party. Persistent biting flies attack the party constantly without a second of reprieve. This prevents them from resting properly; each day they spend in the swamp brings them closer and closer to total exhaustion.

Liminality & Preservation

Bogs are anaerobic, which means they lack oxygen. This also means that things decompose very slowly, if at all, in bogs. This is a common trope in murder mysteries, but that doesn’t mean we can’t use it in our own worlds!

It can also be a good gateway into something a bit more supernatural. The preserved bodies of the dead don’t rest in the Swamp of Sorrows; they rise to vengeance on those who put them there! That’s just a quick example of a hook that utilizes this idea. I’m sure you can come up with more!

Folklore & Legends

I wanted to wrap up with a brief look at some folklore surrounding wetlands. There’s certainly no shortage of it.

I think folklore offers an excellent way to start generating ideas for your own worlds. Hopefully, these examples will inspire you too.

The "Will-o'-the-Wisp”

The classic “ghost light” in the swamp. They’re often portrayed as tricksters or mischievous spirits that want to lure travelers astray. While reality is not nearly as malevolent, there’s no reason it can’t be a bit more so in your worlds.

Bog Bodys

Over the years, scientists have uncovered thousands of bodies that were preserved in bogs. Due to the preservative nature of bogs, some of these bodies are thousands of years old.

Many of the bodies shared a handful of characteristics, which led scientists to believe that many of the bodies may have executed criminals or used as human sacrifices. Now, there’s no way to truly prove it, but it does make for a good story.

Hideouts

Bogs are dense, dangerous, and difficult to navigate; the perfect place to go if you want to disappear. There’s no shortage of stories of outlaws or hermits hiding out in the wilderness, and wetlands fit that bill perfectly. Sometimes, these swamp-dwellers are benign and just want to be left alone. Other times, not so much.

TODO - add 10 from the things to find in a swamp supplement - we can then link to it from here once we post it. Make a task for this on the main milestone when we post this so we don’t forget.

Encounters

To end things, I wanted to provide a handful of encounters that are ready to drop into any wetlands. Use these as is, or as inspiration for your own adventures.

D10
1	Swamp Town - A small town, if it can be called that, materializes in the fog of the swamp. It consists of a dozen or so small shack-like buildings propped up on stilts, raising them a few feet out of the mud. A single tower stands vigil over the community.
2	Giant Water Lilies - A giant lake dominates the swamp. On its surface, thousands of massive water Lillies, most able to support the weight of at least a full-grown man, if not several. Be careful, though, moving between them is fraught with danger and you absolutely do not want to fall into the lake.
3	Hag Hovel - A dirty-looking hole in the swamp that tunnels into the rotting husk of a long-dead tree. Crisscrossing roots create a set of makeshift stairs that descend far deeper than the outward appearance would suggest. At the bottom, an open space containing a myriad of macabre displays: bodies of lost adventurers, cursed potions tempting the unwise, and a cauldron of thick, bubbling, green liquid. Behind you, something else starts the descent…
4	Olrad’s Moss - A moss species discovered by a secretive explorer named Olrad. The moss grows in small quantities, is pink like pork flesh, and is extraordinarily filling.
5	The Huskmen - The towns and villages that border the swamp all speak of the legend of the Huskmen. The legend goes that those who die lost in the swamp become mindless zombies known as the Huskmen. The poor souls are doomed to wander the swamp for eternity, always looking for a way out that they’ll never find.
6	A Dock With Fishing Gear - A clearly old, but still solid, dock juts out about 10 feet into a large pond. On the dock, a tackle box filled with reels and a few live worms, and three fishing poles.
7	Wrecked Boat Parts - Some pieces of a small, wrecked, boat. They’re made of various animal parts, and the larger pieces are covered in a kind of water-resistant wax.
8	Termite-Infested Log - A small log infested with an entire termite colony, queen included. Perhaps a witch or a rodent could find use with it.
9	Altar to Swamp Beast - An altar made of crudely carved stone, covered in moss and other plant life, and caked in most places in a thick layer of mud. Atop it, blood stains and the viscera of what could only be sacrifices to whatever cruel master this altar serves.
10	Werewolf tracks - Clear in the mud, a set of large human footprints. They stagger for some distance, then abruptly stop. Where they do, a large set of canine footprints continues further into the swamp.