Assessing the value of a natural asset is a complicated business. "Everything is connected to everything else" and "the whole is more than the sum of its parts." For instance, how does one put a price tag on a forest? He measures and assigns a value to one ecosystem service it provides while holding others constant, he runs the risk of under-assessing its true worth. Finding an equation to describe the pain of family members left behind by their breadwinners who perished in a landslide after a freak amount of rain was dumped on a denuded forestland is quite tricky.

Be that as it may, one has to pick one quantifiable aspect of natural capital somewhere to start moving. This is where the gift of science becomes a potent tool to allow the interplay of observations and assumptions to be tested.

sednet lecture 300pxMembers of the national and local technical working groups of the Philippine Wealth Accounting and Valuation of Ecosystem Services (Phil-WAVES) for Southern Palawan went through a four-day hands-on training on the use of SedNet, a modeling tool that can assist technical professionals, planners, and policy-makers understand the impacts of land use changes in the upstream region of a watershed on riverine health in terms of sediment deposition and nutrient transport.

Organized by the Phil-WAVES Technical Assistance Team with support from the World Bank, the training was held on April 21 to April 24, 2015 in Puerto Princesa City.

The SedNet, which stands for Sediment and Nutrient Budgets for River Networks, was developed by Australia's CSIRO Land and Water Flagship. The "sediment and nutrient budgets" as used in this context simply refers to the major sources, flow, and deposition of sediment and nutrients in the river network.

The tool can give an account of suspended sediment deposits in floodplains and accumulated sand and gravel in river beds which reduce production of freshwater planktons and algae, which ultimately affect negatively fish and benthic invertebrates that depend on them, and more importantly the sources of these sedimentation and nutrient deposits.

sednet all 300pxThe effect of any changes in watershed, such as conversion of forest to agricultural crop, on erosion of sediments can be simulated to project future riverine sediment loads and determine the optimum combination of management strategies within the watershed (e.g. "Should we leave barren land to sit idly for the years to come?"), especially in the upstream or headwater area, to enhance watershed's ability to support life and maintain natural balance in the entire ecosystem. #

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