Watershed services of tropical forests: from hydrology to economic valuation to integrated analysis

‘Watershed services’ provided by forest ecosystems are receiving increasing attention in the research and policy arena. Changes in forest cover in tropical regions take many different forms and result in multi-dimensional changes in watershed processes: soil erosion rates, peak and low-flow levels, groundwater recharge rates, and water quality. These changes are in turn mediated by the socio-technical context to create a variety of context-specific human impacts, which constitute watershed ‘services’ (or ‘dis-services’). Over the past decade, understanding of the biophysical linkage has generally become nuanced. But large gaps remain in regions like south Asia and Africa and on the question of how different types of forest transitions affect low flows, and the socio-hydrological links are inadequately studied. Economic valuation studies are still plagued with conceptual errors, oversimplified biophysical models, lack of social and technological context, and focus on lump-sum numbers. Greater integration of concepts, methods and latest results, and attention to context-specificity, are required for generating policy-relevant insights.