How Do Bogs Form?

What Is a Bog?

While the word "bog" conjures up images of Irish and Scottish highlands or quaking tar pits for most of us, the truth is that bogs are quite common around the world. Literally defined, a bog is a nutrient-poor, acidic wetland. Most bogs are rich in sphagnum moss, wildflowers, heath plants, insects and plants that prey on insects.

How Bogs Form

Bogs form when thick mats of vegetation like sphagnum moss and sedges decay in a waterlogged environment. You're especially likely to find bogs around the edges of lakes or ponds that are slowly filling in with sediment. Over time the decaying, waterlogged plants form a fibrous layer known as peat. New plants take hold in the peat, holding it together with their root systems, then die, decay, and become part of the peat layer themselves.

Low Biodiversity

The dense, fibrous peat that makes up a bog stifles the flow of water. Nutrients needed for plant growth, such as nitrogen, are in short supply. As vegetation decays, it releases organic acids into the bog. The more acids are present the slower nutrients like nitrogen will be released into the bog. The bog becomes a hostile growing environment for most plants, although some plants such as sphagnum moss and cranberries have adapted specifically to the bog environment. As the peat layer grows thicker it further inhibits the circulation of water and nutrients, in turn slowing the process of decay and nutrient release.

Dangerous Bogs

Bogs may contain anywhere from 90 to 98 percent water and only 2 to 10 percent solid peat. While a thick carpet of growing material, especially sphagnum moss, over the top of the peat may make the bog seem as though it's solid, it's easy to punch straight through this living carpet into the watery mass below, which may be anywhere from 6 to more than 60 feet deep.

Burning Peat

Peat was traditionally cut out of the bogs, dried, and burned for fuel in countries like Ireland, Scotland and Wales. In some small communities you may still find this practice being pursued. Workers, usually the men, cut a trench into a peat bog, lift the peat out in bricks, and leave them to dry. Once dried, the peat bricks are stacked and then used for fuel as needed.

The Difference Between Fens and Bogs

Fens and bogs are similar, waterlogged habitats, but have one critical difference. While bogs are acidic and receive their nourishment from a stifled flow of nutrient-poor rainwater, fens are nourished by mineral-rich groundwater and thus tend to be alkaline in nature.