This paper recapitulates very briefly on the results on many years of landscape-based research into the structure and change of forests in the Kostomukshsky Strict Nature Reserve (Zapovednik) and the Kalevalsky National Park, which has been administratively merged with the former (occupying nearly 1240 km2 in total). Forests cover, respectively, 90 and 80 % of land in these protected areas. They are the key biotic component that shapes and maintains the environment of these ecosystems. The studies were based on an original classification and map of landscapes designed according to the zonal-typological principle. Both areas lie within a tectonic-denudation, hilly-ridge (with a complex of glacial landforms) moderately paludified landscape, with a prevalence of pine habitats. Within this landscape we have distinguished, mapped and described geographical localities (or local landscapes) – its largest morphological units (several thousands of hectares on average). As opposed to geographical landscape, geographical locality features not just a prevalence but a predominance (> 90 % of the area) of certain landforms, of the same genesis, with very narrow variation in open mire and paludal forest percentage, as well as an obvious prevalence of pine or spruce stands. Three and four types of localities have been identified and described for the strict nature reserve and the national park, respectively. Their descriptions are roughly structured as follows: 1) general landscape characteristics of the area (geological-geomorphological features, paludification, soil cover); 2) forest massif structure (dominant composition and types of forest, their ratios and spatial arrangement); 3) genesis and natural dynamics of forests. We specifically highlight the conservation significance of the zapovednik’s and park’s forests inside the protected areas network. Overall, the structural dynamic organization of the massifs constituting the forest cover has been demonstrated to vary substantially, and in some types of localities even strikingly. Almost all the forests have emerged in the sites burnt by forest fires of varying intensities at different times in the past. We argue that the forest cover can only continue to develop in a natural way if the natural fire regime is maintained or lightning-ignited fires are allowed to propagate. This way, the forest cover can exist in a steady dynamic equilibrium, governed only by global climate fluctuations. The zapovednik and the park have preserved within their territories pristine, chiefly pine, forests, which constitute the largest massif in the west of the Eurasian boreal zone. Hardy any of such forest has survived in the extensive land span west of this area and to Norwegian fjords. These forests have formed in Fennoscandia’s most common and widespread type of geographical landscape. The significance of these areas as components of the protected areas network and a key element of the Green Belt of Fennoscandia is demonstrated.