Globally, peatlands are highly diverse, especially with respect to species and community composition. They have, however, much in common with respect to their ecohydrological functioning. A classical distinction is between bogs – which lay higher than their surroundings (“high mires”) and are only fed by precipitation – and fens in landscape depressions (“low mires”) – which are also fed by water that has been in contact with mineral soil or bedrock. Bogs prevail in wet climates whereas fens are ubiquitous.

Brown = peat. Arrows = water flow.