Land use in watersheds of the Venezuelan Andes: A comparative analysis

The influence of deforestation on tropical watersheds has received limited study. We compared seven catchments in the Venezuelan Andes to examine variation in the relative extent of forested versus disturbed land and the potential consequences of changing land use on river ecosystems. These watersheds formed a northeast (Río Acarigua) to southwest (Río Bumbun) transect and exhibited a gradient in readily observable human settlement and disturbance. Overall, forest cover increased and agriculture and pasture land decreased from the Acarigua to the Bumbun. Human building density and road density showed a parallel trend. Catchments varied in intrinsic characteristics as well. Catchments to the northeast originated at lower elevations and had wider, flatter valleys in the lowest piedmont zone, compared with rivers to the southwest. All seven catchments had broadly similar forest cover at approximately 50-60% within the lowest (200-800 m) elevation zone, but they exhibited a strong gradient in the amount of forested versus disturbed land in zones at 800-1400 m and 1400-2600 m. Although the number of buildings was greatest in the 200- to 800-m zone, building density was greater in the 800- to 1400-m zone for the more disturbed catchments, possibly reflecting the areas suitable for coffee production. Land-use change within these catchments is likely to alter hydrology, sediment transport, and habitat conditions within river systems, with adverse consequences for aquatic biodiversity.