Soil erosion in agricultural watersheds consists of a natural (geologic) component and an accelerated (human-induced) component. There is little information available, particularly in developing countries, on the accelerated component of soil and nutrient erosion, or its effect on agricultural sustainability. Lakes and watersheds are physically linked ecosystems, and lake sediments preserve historical records of material export from watersheds. We used paleolimnological methods to calculate sediment accumulation rates for four lakes in Yunnan Province, China. We estimated trap efficiencies of three of the lake basins, calculated recent erosion rates for their watersheds, and calculated low-disturbance rates that approximate natural erosion. Human activities in recent centuries caused a 15-fold increase relative to natural erosion rates of non-carbonate, clastic materials from two small [350 km2 (135 mi2)] watersheds. Phosphorus export from these watersheds increased approximately 19 fold. The degree of human influence appeared to differ between the two larger [2700 km2 (1042 mi2)] watersheds. Accelerated soil and nutrient erosion rates from Yunnan watersheds are high, and may ultimately destabilize agricultural productivity and the agrarian economy.