Formation

What are peatlands?

Peatlands, mires, bogs and fens - what are they and how do we tell the difference between them? The multitude of terms and inconsistencies in their definitions complicates any attempt to study peatlands. To clarify the situation and reflect the accepted terms used in recent European literature, we will use the following definitions of these keywords throughout this site;

• Peatland - an area with a naturally accumulated peat layer at the surface
• Mire - a peatland where peat is currently forming and accumulating
• Bog - a peatland which receives water solely from rain and/or snow falling on its surface
• Fen - a peatland which receives water and nutrients from the soil, rock and groundwater as well as rain and/or snow

Peat

The simple definition of a peatland is an area where peat is found. Peat, or turf as it is often called in Ireland, is a type of soil that contains a high proportion of dead organic matter, mainly plants, that has accumulated over thousands of years. Close inspection can reveal the types of plants that grew, died and accumulated to form a piece of peat.

Unlike most other ecosystems, the dead plants in peatlands do not decompose. This is because of waterlogged conditions, where the lack of oxygen prevents micro-organisms such as bacteria and fungi from rapidly decomposing the dead plants. The formation of peat is a very slow process, and it takes approximately 10 years for 1cm of peat to form.

The factors which cause peat to accumulate may be the same the world over, but different types of peatlands develop because of differences in climate, soil type and plant species. Even within Ireland, different types of peatlands have developed because of varying conditions.

Our peatlands can vary in terms of the plants that grow there, the colour and composition of the peat, the water content and the amount of nutrients the peat contains. There are many different systems for classifying peat. For example, traditional turf-cutters simply classified the peat depending on its colour, as this indicated its fuel value.

In Ireland we can divide our peatlands into three main groups: fens, raised bogs and blanket bogs. The main differences between the three peatland types are listed below: