Andean ecosystems are among the most diverse and threatened ecosystems in the world. Only very general data on the extent and impacts of the transformation processes that have affected ecosystems in Colombia are available to date. This study analyzes the transformation of forests in part of the Eastern Colombian Andes, using the landscape ecological approach, with remote sensing, fieldwork, and GIS. There are two levels of analysis: a regional level (1: 500,000) covering 4.1 million ha and a subregional level (1: 50,000) covering 225,000 ha. The former covers the central portion of the East-Andean Cordillera, where the remaining forest and páramo areas were quantified and their spatial distribution analyzed. The subregional analysis level is located in the Middle Chicamocha Watershed. The effects of human activities on the ecosystems were analyzed, taking current farming systems into consideration. The historical human impact in the region has been intense, especially in the drier parts of the study area. At the regional level, only 22% of the original forests remain, of which 28.7% are located in the national parks. In the subregional study area, only 7.6% remain, mainly at altitudes of more than 3000 m. Of five identified forest types, the two with considerable covered areas were the High-Andean Polylepis Forests (33.6%) and the High-Andean mixed forests (35.1%). The original land cover of the sub-Andean dry forests has been almost totally replaced by seminatural shrublands, pastures, crops, and severely degraded areas. The largest fragments are Andean mixed forests and the Andean oak forests, with sizes up to 866 and 1182 ha. Of 19 identified farming systems at the subregional level, only 5 include substantial proportions of their original forest covers.