The rates of soil erosion and sediment yield in tropical and subtropical savannas around the world have increased dramatically in the past century leading to widespread land and water degradation. The loss of permanent natural vegetation and soil disturbances through the expansion of croplands and overgrazing is widely accepted to be the main driver of increased surface and gully erosion. However, the timelines of change and underlying hydrological and geomorphological mechanisms are complex. In the Brazilian Cerrado, expansion of industrial agriculture since the second half of the 20th century has drastically increased the rates of surface erosion. In East Africa, the scramble for livelihoods and associated combination of a loss of permanent savanna and increasing livestock densities have resulted in accelerated rates of soil erosion, and rapidly incising landscape by expanding gullies. In the tropical savannas of Australia, a significant proportion of sediment yield originates from large alluvial gully complexes on cattle paddocks, whose origins and expansion can be traced to the introduction and increasing densities of livestock from the 1860s onwards. In all cases, land degradation and gully incision triggers geomorphic regime shifts by accelerating the removal of soil, nutrients, water, and seeds from the landscape, prohibiting natural stabilization and recovery. These degraded landscapes expose the natural vulnerability of underlying tropical soils. They lose their buffering capacity to extreme climatic events, wherein high erosion and sediment yield can completely strip the topsoil from large areas of the landscape. This situation requires both alleviation of land use pressures and active landscape restoration efforts tailored to local environmental and socio-economic conditions. Since the resource needs of the human population continue to grow, urgent and widespread action on halting soil and water degradation is required.

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