The Flow Country is one of the largest and most intact known areas of blanket bog (a globally rare ecosystem type) in the world. It demonstrates the development of unusually diverse systems of patterned surfaces on blanket bog, whereas elsewhere in the world, though analogous patterns occur, they are on different forms of mire. The floristic composition of the vegetation is unique in the world and represents a highly Atlantic influence on plant distribution and vegetation development.
The area supports a tundra-type breeding bird assemblage showing general similarity to, but specific differences from, that occurring on arctic-sub-arctic tundras. Significant proportions of the total breeding populations of certain bird species in Europe occur here. In essence, the outstanding importance of these peatlands lies in their total extent, continuity and diversity as mire forms and vegetation complexes, and in the total size and range of species composition of their bird populations.