###### Abstract
Forest coverage depends on the amount of land suitable for agriculture in the territory of the country. In Norway where there are many mountainous areas, the lands suitable for agriculture were utilized, while the unsuitable ones remained overgrown with forest. Since there was not much land suitable for agriculture, the territory of the country remained forested [13]. Dynamics of forest cover were different in different countries over time, determined by historical and socioeconomic reasons [13; 20; 21]; therefore, in order to get a complete picture of the change, it should be examined in more local areas, without generalization of regions. The forest coverage was quite high in the territory of the Republic of Lithuania compared with Western Europe, although the area was suitable for the development of pastures and agricultural activities. In the study of [PERSON] et al. [13], the territory of the Republic of Lithuania is studied as a single research unit together with the republics of Latvia and Estonia. It was determined that there are 35.1% of land suitable for agriculture in this territory. There was 93% of forest areas on the land suitable for farming in 1000 BC, 91.8% in 500 BC, 84.4% in 1 AD, 77.9% in 500 AD, 71.7% in 1000 AD, 37.2% in 1350 (plague pandemic period), 43.9% in 1400 AD, and 6.1% in 1850 AD. This study reveals the general trends of forest cover loss on this territory; however, it is a generalized study that covers three states as a single unit and does not reflect the situation in Lithuania. In order to learn the processes that took place more thoroughly and understand their trends, the study should use local territories and more accurate and less generalized data that can be obtained from contemporary studies, statistical data, and cartographic material. After the examination of the statistical data and the contemporary studies, it can be said that there were much more forests in the territory of Lithuania [15; 22]. Scientists use different methods to study forest change: they study lake sediment, pollen deposits, historical data, statistics, historical military topographic maps, etc. [23; 24; 25; 26; 27; 28]. Topographic maps are great sources of information as they are a unique image of the area mapped out at a given time. They capture spatially oriented information; examining the old military topographic maps makes it possible to look at the surface cover that existed at that time [29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39]. Comparison of the information in the maps compiled chronologically, it is possible to monitor changes over time. Various scientists use this material as a source of information to study landscape changes, cover changes, urbanization development, etc. [39; 40; 41; 42; 43; 44; 45; 46; 47]. Remote monitoring data can be used in a complex way. The use of historical GIS technology allows us to spatially orient all data obtained from different sources according to a unified system, unify the data format, and perform modelling, spatial, and statistical analyses. This helps better understand the processes, dynamics, and trends that took place. In order to plan forest areas and implement their regulation, it is important to know and understand trends of their change, understand which forest areas have remained unchanged over the centuries and how many areas have been cut down/replanted. In different regions, the trends of forest cover area change are different [27; 48; 49; 50; 51; 52; 53; 54]. This study can help understand the importance of the application of historical GIS technology to studying the extent of forest cover change and the factors influencing it in Eastern European countries. These countries are related by similar historical and environmental conditions. Estonia, Latvia, Lithuania, and Poland are in the same climate zone, have similar areas of land suitable for farming, and have a similar history. They were all part of the Russian Empire since the 19 th century. Exploitation and maintenance of forests were influenced by the same legal base and the same state interests.