The possibility of analyzing environmental data using a GIS approach is a very useful assistance in forest management. A case study was performed in some parts of the northern forests of Iran with an area equal to 1033 km2. These forests have individual economical and environmental characteristics, so it is necessary to protect them, seriously. To provide a comprehensive protection planning in these forests, it is essential to study spatial distribution of forest changes related to environmental parameters. Five environmental parameters were concerned including slope, aspect, elevation above sea level and distance from roads and residential areas. The aim of this study was to provide a description of spatial distribution of forest changes related to the above environmental parameters. To meet this aim, environmental factors have been derived from different data sources. Based on aerial photos dating 1967 and 1994, digital topographic – thematic maps in these two years have been prepared. According to these maps, the forest area in the north of Iran was decreased about 141572 hectares (7.1%) in this period. In this research, as a part of a comprehensive project, forest maps including an area of 78806 hectares were extracted from 1: 25000 digital maps in 4 watershed basins separately at the first and the end of the period. These maps later converted from vector to raster format. By comparing these two maps, forest decrease map was obtained. A precise digital elevation model (D EM) having a spatial resolution of 30 meters was produced. Based on the digital elevation model, different parameters including elevation, slope and aspect classes were achieved. The roads and residential areas were also extracted from digital maps and then related classes representing the distance from these features were concluded. Each of these classified maps was multiplied by forest decrease map to determine the role of them in reducing the area of the forest. By comparing forest decrease m
