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Headwaters are the zero-to-first-order catchments that form the upstream margins of all river basins. Environmental changes in headwaters, not least deforestation, can affect the quantity and quality of the water resources downstream. Headwater control is a philosophy that strives to link the perspectives of the applied scientist with the practitioner and policy maker. It emphasises practical, field scale, action research and integrated environmental management strategies that work within nature and with local communities. In Slovakia, Central Europe, where economic transition has affected forest management, measurements of sediments in 27 small headwater reservoirs showed a negative correlation with the degree of forest cover. In Honduras, Central America, where forest conversion is caused by the agricultural colonisation of very steep slopes, accelerated sediment production is not constrained by conventional cross-slope barriers of Vetiveria zizanioides (vetiver grass). Assailed by Hurricane Mitch, the steepest (65–75%) slopes became source areas for landslides that removed around 600 times more sediment than that removed annually by surface wash, producing sediments that buried fields and choked water courses down-slope. The grass barriers did little to prevent landslide generation, but deep-rooted trees might have been more effective. Achieving sustainability in such environments will require a longer term perspective on the significance of environmental extremes and the dangers of building reliance on structures that halt only smaller range events. [Copyright &y& Elsevier]