The future for tropical rivers: Scientific discovery in an age of rapid change
Tropical rivers harbor an extraordinary diversity of freshwater organisms and continue to be frontiers for new scientific discovery. Biological inventories of previously unexplored geographies and application of modern research techniques have led to a rapid growth of knowledge of tropical freshwater biota in recent years. The life histories of tropical freshwater biota, which includes many migratory organisms, are adapted to the hydrologic, chemical, and geomorphologic characteristics of tropical rivers. However these conditions are increasingly subject to change. Shifts in climate patterns, particularly precipitation and temperature, affect the hydrology of tropical rivers, as well as the tropical freshwater biota that are adapted to natural flow regimes. Tropical rivers are now frontiers for dam construction, evidenced by the hundreds of hydropower projects in operation, under construction, or planned for the Amazon and other large tropical river basins. The emergence of megaprojects unprecedented in size and investment—such as the Nicaragua Canal—is further transforming freshwater ecosystems. Landscape change, as a result of deforestation, agricultural expansion, and urbanization, is accelerated in parts of the African and American tropics when compared with the temperate zone, with varied consequences for freshwater ecosystems.
Tropical rivers present a range of opportunities for ecological studies, and the rapid changes occurring worldwide have created an urgent need for applied research. We summarize global trends in transformation of tropical rivers as a consequence of climate change, megaprojects, and landscape alterations, with focus on East Africa, Central America, and the tropical Andes regions. We also identify critical research needs for elevating scientific understanding of tropical freshwater biota, given these global trends transformation of tropical rivers. Finally, we provide recent examples of how ecological research has helped inform management strategies for tropical rivers in light of ongoing change.