Can you tell a swamp from a fen from a bog?

Today’s song comes from Tool – Swamp Song.  Artwork © Lauren Delora Sears.

I remember my first trip to Stewart Island. We had been dreaming about it for years and the whole family had wanted to go.

Ever since the children are small we had taken them tramping.The eldest of our three girls had regular overnight trips. Back then, there was no Kathmandu clothing stores. If I wanted it I had to make it myself. It wasn’t the done thing to be taking young children out into the wilds. Some of our friends and family thought we were mad but, for us, it seemed pretty natural. After all, babies are extremely portable and it doesn’t take long for them to become accustomed to sleeping in strange and often uncomfortable places. Which is more than I can say for some adults.

The second time we flew in and landed on Mason Bay. The beaches are spectacular and the peaceful surroundings is nothing short of idyllic. Apart from the sandflies, of course.

These holidays I’ll be returning to Stewart Island. This time without the kids.

I have been bemoaning the lack of exercise, lately, due to the nature of the study I’m undertaking. So my partner has kindly organised a trip around the Northwest Circuit. By all accounts it is relatively straightforward for someone with the level of tramping experience that I have. Nevertheless, there is the mud to contend with. Mud and I have never really got on ever since my early tramping days in the Waitakere ranges in Auckland. If there is a chance of me ending up on my backside in it, I will. Goodness knows how I survived the Dusky Track, in Fiordland. Mind you, eighteen months ago I was a lot fitter.

So we’re off for two weeks R&R in the middle of next month.

I started to wonder why it is that Stewart Island is so famous for its mud? Everyone who goes there talks of its bogginess. Is it different from other wetlands? Come to think of it, what is the difference between a swamp, a bog and a fen?

It’s something I haven’t really thought about before; one soggy patch of ground seems much like another. Especially when you’re up to your shins, or worse, in it.

Apparently, different wetlands have different geology, topography, water regime and levels of acidity and nutrient levels.

Swamps often form in depressions surrounded by slopes of adjacent land which provides a rich supply of nutrients. There are usually small streams and the water table is above ground. The typical vegetation is flax, sedges, reeds and rushes.

Wire rush credit: Lauren Delora Sears

Fens are slightly acidic and form on slight slopes or at the toe of hillsides. They are peaty because they are waterlogged and don’t have enough oxygen present to allow full decay of the plants. Fens lie in between swamps and bogs on the wetland scale.

It’s the bog that we’ll most likely encounter on Stewart Island. The island has a lot in common with the peaty, blanket bogs of Scotland. They are poor in nutrients because they usually occur on level ground or very gentle slopes and the only source of water is rainfall. They don’t support the larger vegetation of swamps and fens. You’re more likely to encounter mosses and cushion plants. In fact Stewart Island has widespread cushion bogs. And on the North West circuit there will be lots of heath plants – which is where ‘heather’ comes from. Stewart Island has a mass of granite outcrops, again like, Scotland. They often go hand in hand with peat bogs.

We’ll get to spend a lot of time up close and personal with the bogs on Stewart Island. I wonder if they ever made whisky there…