Drainage divide migration and implications for climate and biodiversity

Drainage divides separate Earth’s surface into individual river basins. Divide migration impacts the evolution of landforms, regional climate, ecosystems and biodiversity. In this Review, we assess the processes and dynamics of divide migration and offer insights into the impact on climate and biodiversity. Drainage divides are not static: they can move through the processes of gradual migration that is continuous in unsteady landscapes, or sudden through infrequent river capture events. Divides tend to move in the direction of slower erosion, faster uplift or with horizontal tectonic advection, with rates typically ranging between 0.001 and 10 mm year −1 , and a global average of 0.6 mm year −1 . Evidence of river capture, such as a sharp change in flow direction with an upstream waterfall, can constrain divide migration history. Topographic metrics, such as cross-divide steepness, can predict the migration of drainage divides towards directions with a lower topographic steepness. Divide migration influences the spatial distribution of regional precipitation, temperature and topographic connectivity between species, thereby affecting biodiversity. For example, freshwater fish can migrate into a new drainage basin through river capture, potentially increasing the species richness. Future research should couple advanced landscape evolution models and observations from field and remote sensing to better investigate divide migration dynamics.