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The watershed-ecosystem concept provides a spatially bounded framework within which many aspects of material flux and consequent ecological change can be characterized and quantified, and their interactions studied on a wide range of temporal and spatial scales. Thus in any analysis of the environmental aspects of desertification, lakes and near-shore marine environments provide some of the most favourable opportunities available. This is especially so with the advent of several new techniques using magnetic and short lived radioisotope measurements. The present account focuses on these new techniques and their applications. ‘Mineral’ magnetic measurements can be used to (i) speed and enhance quantitiative estimates of both past and present sediment yields in eroding catchments (ii) identify past and present sediment sources (iii) establish areas of soil depletion and redeposition and …