## 2 Materials and Methods  
### Field of the Research  
The aim of this study was to carry out monitoring of forest cover change and its trends over the longest possible period of time with the use of different data sources; application of historical GIS technologies; and spatial, statistical, and analysis methods, including the analysis of data of different origins in a combined manner. In most cases, only one type of data source is used for studies of the forest area change. It can be maps, cadastral data, pollen remains, and other things depending on the research methodology. Also, the past and present forest cover of the territory is often assessed separately. This narrows the scope of the results and prevents researchers from obtaining a complete picture of changes in forest cover and the identification of change trends. This article, through the application of the methods of historical GIS analysis, proposes to apply a complex methodology of data use, including former forest coverage that was present over a period of 158 years, forest coverage that is currently declared, and an actual one are estimated by combining different data sources. The areas of permanent forest cover were determined and the age of the trees was analyzed. This proposed research methodology makes it possible to evaluate past and present situations comprehensively and perform an analysis of changes in forest cover over a period of a couple of hundred years or more. The research period is limited only by the availability of data. The research area was selected using the case analysis and taking the administrative unit of the Republic of Lithuania in order to demonstrate the proposed methodology for the assessment of changes in forest cover. First, the decision was based on the choice of administrative division of the territory since it has changed several times in the last 200 years. In order to make the territory chosen for the study more suitable to the modern user, the current administrative division of the territory was chosen for the case analysis (Figure 1). The current Republic of Lithuania is divided into 60 administrative units--district municipalities (Figure 1). Jurbarkas District, located in the middle part of Lithuania, was chosen for the case analysis through the application of the criteria listed below. Figure 1: Administrative division of the Republic of Lithuania and Jurbarkas District (with land productivity scores in them). Jurbarkas District occupies an area of 1507 km\({}^{2}\), population density is 17 people/km\({}^{2}\). There is Karsuva forest in the western part, since ancient times. Viesvile State Nature Reserve has been established there. The forest itself is included in the network of Natura 2000 sites. Economic activity has been suspended in some of the state-owned forest plots. The following criteria were applied when choosing the location of the case study, in order to select the most optimal region:  
Criterion I. After reviewing the studies published by other researchers about the shrinking of forests in Europe, it can be seen that in research papers [10; 13; 36; 38; 45; 47; 54], the shrinking of forests is associated with anthropogenic activities and the size of areas suitable for agricultural activities. In order to investigate the extent to which the productivity score influenced the change in forested areas, the land productivity score was taken into account when choosing the research area; therefore, an analysis of the districts was carried out according to the size of the prevailing land productivity score. The land productivity score in Lithuania is from 27.16 to 55.27 (in elderships) ([[https://www.geoportal.lt/map/#](https://www.geoportal.lt/map/#)]([https://www.geoportal.lt/map/#](https://www.geoportal.lt/map/#)), accessed on 3 March 2022). There are no data for one eldership (Figure 1). The aggregated productivity score in the district municipalities ranges from 28.32 to 51.64. The study grouped productivity scores in 5-point increments starting at 27.1. Five groups were obtained (hereinafter--gr.