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Mountain Research and Development

Vol 20

No 3

Aug 2000: 236–245

Andrés Etter and L. Alberto Villa

236

Andean Forests and Farming Systems in part of the Eastern Cordillera (Colombia)
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 inColombia 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 theEast-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 drierparts 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 originalland 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. Keywords:Landscape change; biodiversity; landscape ecology; farming systems; forest remnants; tropical mountains; Eastern Andes; Colombia. Peer reviewed: April 2000. Accepted: May 2000.

Introduction
The ecosystems of the Andes are currently considered high-priority conservation areas. The reasons for this include their high levels of biodiversity and endemism (Andrade 1993; Gentry 1993; Dinerstein et al1995), their great value in terms of environmental services such

as hydrologic regulation and soil conservation, and especially their accelerated rates of destruction (Etter 1998). Andean ecosystems are thought to host over 40,000 plant species (Gentry 1995), contributing significantly to Colombian and global biological diversity. Depending on the altitude belt, only 18–25% of the originalColombian Andean forest ecosystems remain (Etter 1998). These ecosystems are being threatened by colonization and planting of illegal crops (Cavelier and Etter 1995). Human occupation of the Colombian Andes dates back to at least 13,000 BP (Van der Hammen 1974, 1992). Etter and Van Wyngaarden (2000) developed a general analysis of ecosystem transformation relating rural population density totransformation at the national level over the last 500 years. This study shows the long and extensive impact of human activities, especially in the Andean region. In Colombia, the spatial distribution of natural remnants is uneven (Etter 1998). The inner side of the main Andean mountain ranges has historically been subject to greater impacts since they have been more intensely and permanently occupied.When the Spaniards arrived, the study area in the Chicamocha region was already occupied by well-established chiefdoms, with high population densities, at altitudes ranging from 1000 to 3000 m (Langebaeck 1987). Man has thus played a highly significant role in the historical configuration of the actual landscapes. The transformation of the original ecosystems by different farming systems caused...