Assessing Major Environmental Issues in the Caribbean and Pacific Coasts of Colombia, South America

Abstract

Caribbean and Pacific rivers of Colombia exhibit the highest sediment yields of all medium- to large-sized rivers of South America due to the interplay of (1) high rates of runoff (1750–7300 mm yr −1 ), (2) steep relief within catchments, (3) low values of discharge variability ( Q max − Q min ), (4) episodic sediment delivery due to either geologic events or climatic anomalies, and (5) high rates of deforestation and soil conversion due to human activities. In the Magdalena River, many anthropogenic influences, including a forest decrease by 40% in a 20-year period, an agricultural and pasture increase of 65%, poor practices of soil conservation and mining, and increasing rates of urbanization, may have accounted for the overall increasing trends in sediment load on a regional scale. These increasing trends in sediment load coincide with the overall decline of live coral cover in a 145 km 2 coral reef complex in the Caribbean Sea, the Rosario Islands. After three decades of sampling, live coral cover remaining in the area is only 23%. In the Pacific coast, the diversion of the Patía River has caused major environmental impacts, including distributary channel erosion, sediment deposition, mangrove die-off, delta-front erosion, changes in fishing resources, transportation and communication difficulties, and changes in lifestyles. This is the most impressive environmental change documented for any coastal system along the western coast of South America. The synthesis presented in this chapter is just the first step toward understanding the natural and human-induced factors that have produced the observed patterns of water discharge and sediment load into Pacific and Caribbean coasts of Colombia and to relating these processes to the impact on coastal ecosystems.