A negotiation support tool for assessment of land use change impacts on erosion in a previously forested watershed in Lampung, Sumatra, Indonesia

Land use is changing rapidly in SE-Asia from forest to landscape mosaics with various degrees of tree cover. The relations between impacts at these different scales should recognize a range of 'lateral flow' and 'filter' phenomena. To develop concepts and an appropriate methodology, ICRAF and partner institutions study land use and its change in Sumberjaya, West-Lampung, Sumatra an area of about 730 km2, which encompasses a watershed, that was transformed in the past three decades from a large forest cover to a mosaic of coffee farms with rice paddies in the valleys and which has seen quite some conflict over the past 10 years. For risk assessment of erosion and consequent delineation of protection areas various stakeholders convinced of their own ‘rightness’ often only use their own mental model, often based only on strong perceptions and beliefs. The (weak) knowledge base used for evaluating these issues for landscape mosaics covering the wide range between pure forests and purely cropped lands is now challenged by the development of different erosion equations and models over the past ten years. In an erosion modeling exercise various scenarios for the USLE, WEPP and GUEST (Rose) equations are compared at different scales. Results are strikingly different. The methodology is inspired by the one developed for 'Sustainable coastal-zone management, a case study for Southwest Sulawesi'. Aim is to test and validate that methodology in a completely different setting and use it as a discussion tool for various stakeholders.

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