CHANGE DETECTION OF THE EFFECT OF SEVERE DROUGHT ON SUBSISTENCE AGROPASTORAL COMMUNITIES ON THE BOLIVIAN ALTIPLANO

The purpose of this study was to identify the ecological effects of dr ought on the vegetation resources of subsistence agropastoral communit ies on the Bolivian Altiplano. The objectives of the study were to (1) characterize vegetation cover response during a typical year, and (2) identify vegetation cover type's response to drought using an image d ifferencing change detection technique. A geographical information sys tem (GIS), which included multi-temporal (from 1972-1987) Landsat sate llite imagery, was used as the assessment tool. Vegetation index diffe rence images showed that (1) all vegetation types were impacted by dro ught, but the wet meadow vegetation cover type had the least response, and (2) approximately 90 per cent of vegetation cover had not changed between 1972 and 1987. Crop and animal production in agropastoral sys tems are dependant on the availability of vegetation resources. The we t meadow vegetation type was the most resistant to drought, which sugg ests that during drought periods it is a key resource upon which the l ivestock of the community would depend. Little change in vegetation co ver over the 15-year span of the study, and the rapid recovery of this parameter following the drought of 1983-84, suggest that agricultural practices (especially livestock grazing) are not contributing to reso urce degradation when measured only in terms of change in vegetation c over.