Banana Crop Expansion and Increased River-borne Sediment Exports to the Gulf of Uraba, Caribbean Coast of Colombia

摘要

Sedimentation is a major environmental issue in the Gulf of Uraba (southern Caribbean coast of Colombia) (1), yet driving forces and influences on coastal ecosystems are poorly known by local scientists and natural resource managers. This is partially a result of the small temporal and spatial windows employed in scientific studies and management strategies that hide the complex interactions among hydrologic, geographic, and socioeconomic processes operating at basin level. For instance, sediment accumulation in the nearshore has been managed at a local scale by dredging access channels in shoaling areas and by constructing barriers to prevent littoral erosion at other sites, with little recognition of sediment sources and transport (2). Moreover, causes of such problems have not been investigated throughout entire river basins, several of which are world-class producers of banana, and therefore become potential sources of sediments to be transported to the coastal zone. Elsewhere, conversion of native forest to agriculture lands has been implicated as a major driver of increased land erosion and sediment yields (3). Specifically, deforestation and urbanization may have accounted for a positive trend in sediment delivery to the Caribbean Sea through the Magdalena River basin, Colombia's largest system (4). Agricultural lands doubled in area between 1970 and 1990, while sediment loads increased in 17 out of 32 river subbasins. Maximum water discharge and a deforestation index explained 96 percent of the variation in sediment yield across the upper Magdalena basin. Here, I discuss the hypothesis that sediment yields in the Uraba region are greater in river basins with extensive banana crops than in basins under other land covers.