A characteristic of the variety of mire ecosystems of the Green Belt of Fennoscandia (GBF) within the area of the Republic of Karelia is presented. Spectra of mireland types, their size, structure, and dynamics in various landscapes of the GBF were shown. All types of mirelands typical for the western and central regions of Karelia are represented in this territory correspondingly. Most of them are in the natural state, which in general allows the majority of Karelian and Eastern Fennoscandia mire flora species to inhabit the territory. 24 species of vascular plants listed in the Red Book of the Republic of Karelia are found in the mirelands of the GBF. A high growth rate of peat in the narrow interridge depressions of mires was detected during the Holocene. The existing network of protected areas within the GBF does not include the full range of mire ecosystems and their flora, thus it must be optimized and expanded.